Engine Controls - Tests W/codes: Diagnosis Chevrolet Metro I

DTC Types

DTCs are divided into 4 categories: type "A", type "B", type "C" and type "D". Each DTC is directly related to a specific diagnostic test. PCM sets a DTC based on failure of tests during trip(s). A trip is defined as a KEY ON/RUN/KEY OFF cycle which satisfies certain enable criteria for a given diagnostic test. Certain tests must fail 2 consecutive trips before a DTC is set. The following are the 4 different types (categories) of DTCs and their description

Type "A"

1. Emissions related.
2. Requests illumination of MIL on first trip with a fail.
3. Stores a history DTC on first trip with a fail.
4. Stores a freeze frame record on first trip with a fail (if empty).

Type "B"

1. Emissions related.
2. Armed after one trip with a fail.
3. Disarmed after one trip with a pass.
4. Requests illumination of MIL on second consecutive trip with a fail.
5. Stores a history DTC on second consecutive trip with a fail (DTC will be armed after first fail).
6. Stores a freeze frame record on second consecutive trip with a fail (if empty).

1. Special Cases Of Type "B" Diagnostic Tests Misfire diagnostics has a unique ability to alert vehicle operator to potentially damaging levels of misfire. If high misfire levels exist that could damage catalytic converter, PCM will command MIL to flash once every second. When catalyst damaging misfire condition no longer exists, PCM will command MIL to stop flashing.

Type "C" (If Equipped)

1. Non-emissions related.
2. Requests illumination of service light or service message on Driver Information Center (DIC) on first trip with a fail.
3. Stores a history DTC on first trip with a fail.
4. Updates fail record each time diagnostic test fails.

Type "D" (Type "D" Non-Emissions Related Are Not Used On Certain Vehicle Applications)

1. Non-emissions related.
2. Does not request illumination of any light.
3. Stores a history DTC on first trip with a fail.
4. Does not store a freeze frame record.

DIAGNOSTIC PROCEDURE

Diagnosis of computerized engine control system should be performed in the following order

1. Ensure all engine systems not related to computer are operating properly. Check for any Technical Service Bulletins (TSBs) that may apply. DO NOT proceed with testing unless all other problems have been repaired. Perform «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) before diagnosing Diagnostic Trouble Codes (DTCs).
2. If DTC(s) were displayed, determine whether codes are hard or intermittent trouble codes. Hard codes will cause MIL to illuminate continuously while engine is running. See «HARD OR INTERMITTENT TROUBLE CODE DETERMINATION»(ref-189-S37217182882000030800000) . For diagnosing hard codes, proceed to appropriate DTC test. See «DIAGNOSTIC TESTS»(ref-189-S01713383122000030800000) . For diagnosing intermittent codes, proceed to INTERMITTENTS in appropriate TROUBLE SHOOTING - NO CODES article.
3. If no DTCs are present and a driveability problem exists, refer to SYMPTOMS in appropriate TROUBLE SHOOTING - NO CODES article. Doing so will help identify proper system or component to check. See appropriate SYSTEM & COMPONENT TESTING article for diagnosis of faulty component.
4. After necessary repairs are made, clear DTCs, verify vehicle will enter "closed loop" operation, and ensure DTC does not reset.

ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK

Note. Do not perform this check if a driveability complaint is not present.

On-Board Diagnostic (OBD) system check is an organized approach in identifying a problem created by an electronic engine system malfunction. It must be the starting point for any driveability complaint diagnosis, because it directs service technician to the next logical step in diagnosing a complaint. Understanding and using it correctly will reduce diagnostic time and prevent unnecessary replacement of good parts.

1. Check for one or more of the following conditions: Malfunction Indicator Light (MIL) illuminated with engine running. Confirmed customer driveability concern. Suspected fault in computerized engine control system. If any conditions are present, go to next step. If specified conditions are not present, system is okay at this time. Check for an intermittent problem. See INTERMITTENTS in appropriate TROUBLE SHOOTING - NO CODES article.
2. Turn ignition on, with engine off. Observe MIL. If MIL illuminates, go to next step. If MIL does not illuminate, go to appropriate NO MALFUNCTION INDICATOR LIGHT under «CIRCUIT TESTS»(ref-189-S26970648042000030800000) .
3. Turn ignition off. Install scan tool according to manufacturer's instructions. Turn ignition on, with engine off. If scan tool displays PCM data, go to next step. If scan tool does not display PCM data, go to «DATA LINK CONNECTOR DIAGNOSIS»(ref-189-S19988114522000030800000) under CIRCUIT TESTS.
4. Attempt to start engine. If engine starts and runs, go to next step. If engine will not run, go to appropriate NO START-ENGINE CRANKS OKAY under NO START DIAGNOSIS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
5. Observe DTC data. If no DTCs are set, go to next step. If any DTCs are stored, save freeze frame data using scan tool, and go to appropriate Diagnostic Trouble Code (DTC). See «DIAGNOSTIC TESTS»(ref-189-S01713383122000030800000) .
6. If MIL is illuminated and no DTCs are set, go to appropriate MALFUNCTION INDICATOR LIGHT ON STEADY under «CIRCUIT TESTS»(ref-189-S26970648042000030800000) . If MIL is off and no DTCs are set, go to next step.
7. Compare scan tool data with values shown in appropriate SCAN TOOL DATA VALUES table under «SCAN TOOL DATA»(ref-189-S01138772912000030800000) . If displayed values are within specified ranges, suspect an intermittent fault. See INTERMITTENTS in appropriate TROUBLE SHOOTING - NO CODES article. If displayed values are not within specified ranges, diagnose suspect component. See appropriate SYSTEM & COMPONENT TESTING article.

DTC DEFINITIONS

1. The DTCs indicate failure of a specific sensor and/or circuit. Sensor/circuit diagnosis may indicate replacement of PCM.
2. If PCM is replaced at any point during diagnostic testing and if condition is still not corrected after replacing PCM, the following may be the cause: An incorrect PCM may cause a malfunction, which may or may not set a DTC. The PCM connector may be the problem. Connector terminals may have to be removed from connector to be properly checked. Replacement PCM may be faulty. Intermittent problem. Make a careful physical inspection of affected sensor/circuit. A shorted solenoid, coil relay, or harness may be the cause of PCM failure. Use Short Circuit Tester (J-34636) to check for short circuits.

DTC IDENTIFICATION (METRO)

DTC IDENTIFICATION (PRIZM)

HARD OR INTERMITTENT TROUBLE CODE DETERMINATION

Note. DTCs will be recorded at various operating times. Some codes require operation of related sensor or switch for 5 seconds; others require operation for 5 minutes or longer at normal operating temperature, vehicle speed and load. Therefore, some DTCs may not set in a service bay operational mode and may require road testing vehicle in order to duplicate conditions under which code will set.

During any diagnostic procedure, determine if DTC(s) are hard failure codes or intermittent failure codes. Diagnostic procedures will not always help analyze intermittent codes. To determine hard codes and intermittent codes

1. Enter diagnostic mode. Read and record all stored DTCs. Exit diagnostic mode, and clear DTCs. See «CLEARING DTCS»(ref-189-S39841518842000030800000) .
2. Apply parking brake, and place transmission in Neutral or Park. Block drive wheels, and start engine. MIL should turn off. Operate warm engine at specified RPM for 2 minutes and note MIL.
3. If MIL illuminates, enter diagnostic mode. Read and record DTCs. This will reveal hard failure codes. Oxygen sensor related codes may require a road test to reset hard failure after DTCs were cleared.
4. If MIL does not illuminate, all stored DTCs were intermittent failures, except as noted above.

Diagnostic Aids

Diagnostic aids (located in many circuit tests) are provided as additional tips to help with diagnosis when inspected circuit is okay.

SPECIAL TOOLS (DIAGNOSTIC)

Note. Diagnosis of computerized engine control system requires using a scan tool. Use of a scan tool saves a great deal of diagnostic time and prevents replacement of good parts. Computer related diagnosis without a scan tool is NOT recommended.

Computerized engine control system is diagnosed using a Tech 1 or 2 scan tool, or other OBD-II compatible scan tool. However, other tools are needed to aid in diagnosing problems. These tools include a tachometer (inductive pickup), a non-powered test light, digital multimeter with 10-megohm input impedance (minimum), vacuum pump and vacuum gauge, High Energy Ignition (HEI) spark tester, fuel pressure gauge, fuel injector test light (noid-light), and fused jumper wires. A test light, rather than DVOM, must be used when indicated by a circuit test procedure.

SCAN TOOL USAGE

Note. Before connecting scan tool to vehicle, diagnostic system should be checked to determine if system is operating properly, and if information received will be accurate. This is done by performing ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . If vehicle does not pass OBD system check, information received may be invalid.

Note. Information obtained by a scan tool is only as accurate as the scan tool itself. A scan tool that displays faulty data should not be used. If faulty data readings are suspected, verify scan tool information using a digital multimeter and wiring schematic.

Scan tool is a specialized tester which, when plugged into DLC, can diagnose on-board computer control systems by providing almost instant access to circuit data without crawling under instrument panel or hood to backprobe sensors and connectors. Scan tools reduce diagnostic time by furnishing input data (sensor values) which can be compared to specification parameters. See appropriate SCAN TOOL DATA VALUES table under SCAN TOOL DATA .

Scan tools also furnish status data of output devices (solenoids and motors). However, status parameters are only an indication that output signals have been sent to devices by PCM. They do not indicate whether devices respond properly to that signal. This must be verified at output device using DVOM or test light.

If DTCs are not present, a problem may still exist. Driveability-related problems with DTCs displayed occur about 20 percent of the time, while driveability problems without DTCs occur about 80 percent of the time. Out-of-calibration sensors may NOT set a DTC, but WILL cause driveability problems. A scan tool is the easiest method of checking sensor specifications and other data parameters. A scan tool is also useful in finding intermittent wiring problems by wiggling wiring harnesses and connections (key on, engine off) while observing data parameters. See appropriate SCAN TOOL DATA VALUES table under SCAN TOOL DATA .

SCAN TOOL DATA

Note. Information contained in the following tables is typical of readings taken on a vehicle with engine idling at normal operating temperature, throttle closed, transmission in Park or Neutral, system in closed loop status, and all accessories off (except as noted in tables). For additional information, see scan tool owner's manual.

SCAN TOOL DATA VALUES (METRO)

SCAN TOOL DATA VALUES (PRIZM)

Circuit Description

Malfunction Indicator Light (MIL) should remain on when ignition switch is in ON position and engine is not running. Battery voltage is applied to indicator bulb. PCM controls indicator bulb and turns bulb on by providing a ground path through MIL control circuit.

Diagnosis & Repair

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Check for an open in IG-COIL fuse (15-amp) located in passenger compartment fuse box. Also, check for an open in FI fuse (15-amp) located in engine compartment fuse box. If fuse is okay, go to next step. If fuse is blown, go to step 20 .
3. Attempt to start engine. If engine starts, go to next step. If engine does not start, go to step 10 .
4. Install scan tool and select data display. If scan tool displays data, go to next step. If scan tool does not display any data, go to step 10 .
5. Turn ignition off. Disconnect PCM 26-pin connector C1. Back out terminal No. 17 (MIL control circuit) from PCM 26-pin connector C1. See WIRING DIAGRAMS article. Connect a fused jumper wire between ground and MIL control circuit. Turn ignition on, with engine off. Observe MIL. If MIL illuminates, go to step 18 . If MIL does not illuminate, go to next step.
6. Turn ignition on, with engine off. Using test light connected to ground, backprobe instrument cluster connector C1 (harness side) terminal No. 2 (MIL power supply circuit). See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 8 .
7. Turn ignition off. Disconnect instrument cluster connector C1. Using test light connected to battery voltage, probe instrument cluster connector C1 (harness side) terminal No. 4 (MIL control circuit). See WIRING DIAGRAMS article. Turn ignition on, and then off while observing test light. If test light illuminates when ignition is on and turns off when ignition is off, go to step 19 . If test light does not operate as specified, go to step 9 .
8. Repair open in MIL power supply circuit between fuse box and instrument cluster. After repairs, go to step 21 .
9. Repair open in MIL control circuit between instrument cluster and PCM. After repairs, go to step 21 .
10. Turn ignition on, with engine off. Using test light connected to ground, backprobe both PCM 26-pin connector C1 (harness side) terminals No. 2 and 15 (ignition positive voltage circuits). See WIRING DIAGRAMS article. If test light illuminates on both terminals, go to next step. If test light does not illuminate on both terminals, go to step 13 .
11. Using test light connected to ground, backprobe PCM 22-pin connector C3 (harness side) terminal No. 20 (ignition positive voltage circuit). See WIRING DIAGRAMS article. If test light illuminates, go to step 14 . If test light does not illuminate, go to next step.
12. Repair open in ignition positive voltage circuit between IG-COIL fuse and PCM. After repairs, go to step 21 .
13. Check for an open in ignition positive voltage circuit between main relay and PCM. Repair as necessary. After repairs, go to step 21 . If circuit is okay, diagnose main relay circuit. See MAIN RELAY CIRCUIT under appropriate NO START-ENGINE CRANKS OKAY in appropriate BASIC DIAGNOSTIC PROCEDURES article.
14. Turn ignition on, with engine off. Using DVOM connected to ground, backprobe PCM 16-pin connector (harness side) terminal No. 1 (5-volt reference circuit). See WIRING DIAGRAMS article. If voltage is 5 volts, go to step 18 . If voltage is not 5 volts, go to next step.
15. Check for a short to ground in 5-volt reference circuit between PCM and TP sensor, MAP sensor or ISC motor. See WIRING DIAGRAMS article. Also, check related components, such as TP sensor, MAP sensor or ISC motor. Repair as necessary. After repairs, go to step 21 . If circuit and components are okay, go to next step.
16. Turn ignition off. Disconnect PCM 26-pin connector C1. Using test light connected to battery voltage, probe PCM 26-pin connector (harness side) terminals No. 1, 13 and 26 (ground circuits). See WIRING DIAGRAMS article. If test light illuminates on each terminal, go to step 18 . If test light does not illuminate on each terminal, go to next step.
17. Repair open in PCM ground circuits between PCM and ground connections. After repairs, go to step 21 .
18. Replace PCM. Program PCM using required equipment. After replacing PCM, go to step 21 .
19. Check for a faulty bulb, a faulty circuit to instrument cluster, or a faulty connection at instrument cluster. Repair as necessary. After repairs, go to step 21 .
20. Repair short to ground in IG-COIL fuse or FI fuse circuits. After repairs, go to next step.
21. Turn ignition on, with engine off. Observe MIL. Start engine and continue observing MIL. If MIL illuminates when ignition is on and turns off after engine starts, system is okay. If MIL remains illuminated, diagnose DTC(s).

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement. Also, check for any of the following conditions

1. If engine runs okay, check for a faulty indicator bulb, or an open in instrument cluster power supply circuit.
2. If engine cranks, but will not start and MIL is inoperative, check for a faulty main relay.
3. If engine cranks, but will not start and MIL is inoperative along with no scan tool data, check for a short to ground in 5-volt reference circuit, such as TP sensor, MAP sensor or ISC motor.
4. Check for a poor PCM electrical connection.

Malfunction Indicator Light (MIL) should remain on when ignition switch is in ON position and engine is not running. Battery voltage is applied to indicator bulb. PCM controls indicator bulb and turns it on by providing a ground path through MIL control circuit.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Attempt to start and idle engine. If engine starts, go to next step. If engine does not start, go to step 6 .
3. Observe instrument cluster operation. If all other instrument cluster functions operate properly, go to next step. If all other instrument cluster functions do not operate properly, diagnose instrument cluster as necessary. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT.
4. Turn ignition off. Disconnect PCM 22-pin connector C3. Turn ignition on, with engine off. Using a fused jumper wire connected to ground, probe PCM 22-pin connector C3 (harness side) terminal No. 5 (MIL control circuit). See WIRING DIAGRAMS article. If MIL illuminates, go to step 21 . If MIL does not illuminate, go to next step.
5. Turn ignition on, with engine off. Using a fused jumper wire connected to ground, backprobe instrument cluster connector C1 terminal No. 3 (MIL control circuit). See WIRING DIAGRAMS article. If MIL illuminates, go to step 14 . If MIL does not illuminate, diagnose instrument cluster as necessary. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT.
6. Check for an open EFI fuse (15-amp) and IGN fuse (7.5-amp), faulty EFI main relay, and no ignition positive voltage. Repair as necessary. After repairs, go to step 22 . If fuse, relay and ignition voltage are okay, go to next step.
7. Remove EFI main relay located in engine compartment fuse/relay box. Using test light connected to ground, probe EFI main relay connector terminal No. 9 (EFI fuse circuit). See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 15 .
8. Using test light connected to ground, probe EFI main relay connector terminal No. 11 (IGN fuse circuit). See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 16 .
9. Connect test light between EFI main relay connector terminals No. 11 (IGN fuse circuit) and No. 12 (ground circuit). See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 17 .
10. Connect test light between EFI main relay connector terminals No. 9 (EFI fuse circuit) and No. 10 (PCM circuit). See WIRING DIAGRAMS article. Attempt to start and idle engine. If engine starts, go to step 18 . If engine does not start, go to next step.
11. Turn ignition off. Remove fused jumper wire. Install EFI main relay. Disconnect all PCM harness connectors. Turn ignition on. Using test light connected to ground, probe PCM 22-pin connector C3 (harness side) terminal No. 12 (ignition positive voltage circuit). See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 19 .
12. Using test light connected to battery voltage, probe the following PCM harness connector terminals: 26-pin connector C1 terminal No. 13 (ground circuit). 26-pin connector C1 terminal No. 14 (ground circuit). 26-pin connector C1 terminal No. 26 (ground circuit). 16-pin connector C2 terminal No. 16 (ground circuit). If test light illuminates on all terminals, go to next step. If test light does not illuminate on all terminals, go to step 20 .
13. Check for short to ground in fuel tank pressure sensor, MAP sensor and TP sensor reference voltage circuits. Check if sensors are internally shorted. Repair as necessary. After repairs, go to step 22 . If circuits and sensors are okay, go to step 21 .
14. Repair open in MIL control circuit. After repairs, go to step 22 .
15. Repair open circuit between EFI fuse and EFI main relay. After repairs, go to step 22 .
16. Repair open circuit between IGN fuse and EFI main relay. After repairs, go to step 22 .
17. Repair open circuit between EFI main relay and ground connection. After repairs, go to step 22 .
18. Replace EFI main relay. After repairs, go to step 22 .
19. Repair open circuit between PCM and EFI main relay. After repairs, go to step 22 .
20. Repair open circuit between PCM and ground connections. After repairs, go to step 22 .
21. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
22. Turn ignition on. If MIL illuminates, go to next step. If MIL does not illuminate, go to step 2 .
23. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Start engine and let idle. Observe MIL. If MIL illuminates, perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. If MIL does not illuminate, system is okay.

Check for an open in EFI, IGN and GAUGE fuses. Ensure EFI main relay is securely mounted in relay/fuse box. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement. Check for a poor PCM electrical connection.

A steady Malfunction Indicator Light (MIL) with engine running suggests a short to ground in MIL control circuit, or a DTC stored in PCM memory.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Turn ignition off. Disconnect PCM 26-pin connector. Turn ignition on, with engine off. If MIL illuminates, go to next step. If MIL does not illuminate, go to step 5 .
3. Check for a short to ground in MIL control circuit between instrument cluster and PCM. Repair as necessary. After repairs, go to step 6 . If circuit is okay, go to next step.
4. Check for a shorted instrument cluster printed circuit. Repair as necessary. After repairs, go to step 6 .
5. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
6. Start engine and observe MIL. If MIL illuminates for about 3 seconds, and then turns off, system is okay. If MIL remains illuminated, diagnose DTC(s).

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Check for a shorted MIL control circuit between PCM and instrument cluster. A shorted instrument cluster printed circuit may cause MIL to remain illuminated. Check for a poor PCM electrical connection.

A steady Malfunction Indicator Light (MIL) with engine running suggests a short to ground in MIL control circuit, or a DTC stored in PCM memory.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Turn ignition off. Disconnect PCM 22-pin connector. Turn ignition on, with engine off. If MIL illuminates, go to next step. If MIL does not illuminate, go to step 4 .
3. Repair short to ground in MIL control circuit between instrument cluster and PCM. After repairs, go to step 5 .
4. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
5. Start engine and observe MIL. If MIL illuminates for about 3 seconds, and then turns off, system is okay. If MIL remains illuminated, diagnose DTC(s).

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Check for a shorted MIL control circuit between PCM and instrument cluster. A shorted instrument cluster printed circuit may cause MIL to remain illuminated. Check for a poor PCM electrical connection.

Data Link Connector (DLC) is used to communicate with PCM. DLC is located under left side of instrument panel.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. If scan tool displays engine data, system is okay. If scan tool does not display engine data, go to next step.
3. Turn ignition on, with engine off. Using DVOM, measure voltage between DLC power supply circuit and ground. See WIRING DIAGRAMS article. If battery voltage is present, go to next step. If battery voltage is not present, go to step 6 .
4. Using DVOM, measure voltage between DLC serial data output circuit and ground. See WIRING DIAGRAMS article. If battery voltage is present, go to next step. If battery voltage is not present, go to step 7 .
5. Using test light connected to battery voltage, probe DLC ground circuits. See WIRING DIAGRAMS article. If test light illuminates on both circuits, go to step 10 . If test light does not illuminate on either circuit, go to step 8 .
6. Repair open or short in DLC power supply circuit. After repairs, go to step 11 .
7. Repair open or short in DLC serial data output circuit. After repairs, go to step 11 . If circuit is okay, go to step 9 .
8. Repair open(s) in DLC ground circuit(s). After repairs, go to step 11 .
9. Replace PCM. Program PCM using required equipment. After replacing PCM, go to step 11 .
10. Scan tool is faulty. Refer to scan tool manual for repairs. After repairs, go to next step.
11. After repairs are completed, operate vehicle within conditions under which original symptom was observed. If system operates properly, repair is complete. If system does not operate properly, go to «DIAGNOSTIC AIDS»(ref-189-S24564712212000030800000) .

Some scan tools require an external power feed. Ensure correct power feed is being used. Try scan tool on another vehicle to ensure scan tool and/or communication cables are not at fault. Ensure correct vehicle, model year and VIN code is selected on scan tool.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

DIAGNOSTIC TESTS

Note. Before clearing DTCs, record FREEZE FRAME and FAILURE RECORDS for reference during testing. Data will be erased when DTCs are cleared.

Note. If PCM is replaced, NEW PCM must be programmed using special equipment.

Note. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM before proceeding with DIAGNOSTIC TESTS.

PCM uses MAP sensor signals to control fuel delivery and ignition timing. MAP sensor measures changes in intake manifold pressure (vacuum). PCM sends a 5-volt reference voltage to MAP sensor. Changes in pressure, resulting from engine load and RPM, are converted into an output voltage monitored by PCM. As manifold pressure changes, sensor output voltage also changes. See MANIFOLD PRESSURE VS. SCAN TOOL VOLTAGE table. By monitoring sensor output voltage, PCM knows the value of manifold pressure.

MAP sensor is also used to measure barometric pressure, allowing PCM to make adjustments for changes in altitudes. DTC P0105 will set when MAP sensor output is zero kPa, or MAP sensor output is 130 kPa or greater with ignition on.

When DTC sets, MIL will illuminate. PCM will record operating conditions at time of failure and information in freeze frame buffer. PCM will enter Fail-Safe Function using MAP sensor value of 6.8 psi (46.7 kPa) and ignition timing fixed value of 5 degrees BTDC.

MANIFOLD PRESSURE VS. SCAN TOOL VOLTAGE

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S18676001422000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Turn ignition on, with engine off. Using scan tool, monitor MAP sensor parameter. If MAP sensor value is 13-16 psi (90-110 kPa), go to next step. If MAP sensor value is not 13-16 psi (90-110 kPa), go to step 5 .
3. Start engine and let idle at normal operating temperature. Using scan tool, monitor MAP sensor parameter. If MAP sensor value is 3-7 psi (20-50 kPa), go to next step. If MAP sensor value is not 3-7 psi (20-50 kPa), go to step 5 .
4. Using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If DTC P0105 resets, go to next step. If DTC P0105 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S05525661872000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
5. Turn ignition off. Disconnect MAP sensor electrical connector. Turn ignition on, with engine off. Using DVOM connected to ground, probe MAP sensor connector (harness side) reference voltage circuit. See WIRING DIAGRAMS article. If voltage is 5 volts, go to next step. If voltage is not 5 volts, go to step 10 .
6. Using DVOM connected to ground, probe MAP sensor connector (harness side) input circuit. See WIRING DIAGRAMS article. If voltage is 4.9 volts or more, go to next step. If voltage is less than 4.9 volts, go to step 11 .
7. Using test light connected to battery voltage, probe MAP sensor connector (harness side) ground circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 12 .
8. Connect a fused jumper wire between MAP sensor connector (harness side) input circuit and ground circuit. See WIRING DIAGRAMS article. Using scan tool, monitor MAP sensor parameter. If MAP sensor value is zero psi (zero kPa), go to step 13 . If MAP sensor value is not zero psi (zero kPa), go to next step.
9. Check for short to voltage in MAP sensor input circuit. Ensure MAP sensor input circuit is not shorted to MAP sensor reference voltage circuit. Repair as necessary. After repairs, go to step 15 . If circuit is okay, go to step 14 .
10. Check for an open, short to ground or short to voltage in MAP sensor reference voltage circuit. Repair as necessary. After repairs, go to step 15 . If circuit is okay, go to step 14 .
11. Check for an open, short to ground or short to voltage in MAP sensor input circuit. Repair as necessary. After repairs, go to step 15 . If circuit is okay, go to step 14 .
12. Check for an open in MAP sensor ground circuit between MAP sensor and PCM. Repair as necessary. After repairs, go to step 15 . If circuit is okay, go to step 14 .
13. Replace MAP sensor. After repairs, go to step 15 .
14. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
15. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

If DTCs P0105, P0110, P0115 and P0120 are also set, sensor ground circuit may be at fault. Using scan tool, check MAP sensor parameter for a fixed value or a slow response when throttle is snapped.

An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Manifold Absolute Pressure (MAP) sensor responds to changes in intake manifold pressure (vacuum). PCM applies 5 volts to MAP sensor. Changes in pressure, resulting from engine load and RPM, are converted into a voltage signal monitored by PCM. A low voltage reading at PCM indicates low manifold pressure, and a high voltage at PCM indicates high manifold pressure. DTC P0106 will set when

1. Engine speed and throttle position is steady.
2. MAP sensor value at engine cranking differs from engine running by less than .19 psi (1.3 kPa).
3. Barometric pressure differs from MAP sensor pressure by less than .19 psi (33 kPa).
4. Conditions must be present for at least 2 minutes.

When DTC sets, MIL will illuminate. PCM will record operating conditions at time of failure and information in freeze frame buffer. PCM will enter Fail-Safe Function using TP sensor and engine RPM. EGR and EVAP purge control will be stopped.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool, monitor MAP sensor parameter and record MAP sensor value. Start engine and record MAP sensor value. If MAP sensor values changed more than 4.8 psi (33 kPa), go to next step. If MAP sensor value does not change more than 4.8 psi (33 kPa), go to step 4 .
3. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If DTC P0106 resets, go to next step. If DTC P0106 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S09574101572000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
4. Check for damaged, disconnected or misrouted vacuum hoses. Check for a plugged vacuum hose or valve. Check for intake manifold leaks, MAP sensor seal leaks or throttle body leaks. Check for a faulty, missing or incorrectly installed PCV valve. Check for restricted air intake or exhaust system. Repair as necessary. After repairs, go to step 11 . If no problems are found, go to next step.
5. Turn ignition on, with engine off. Disconnect MAP sensor electrical connector. Using DVOM, measure voltage between ground and MAP sensor connector (harness side) input circuit. See WIRING DIAGRAMS article. If voltage is 4.9-5.0 volts, go to next step. If voltage is not 4.9-5.0 volts, go to step 7 .
6. Using DVOM, measure voltage between MAP sensor connector (harness side) reference voltage circuit and ground circuit. See WIRING DIAGRAMS article. If voltage is 4.9-5.0 volts, go to step 8 . If voltage is not 4.9-5.0 volts, go to step 9 .
7. Check for open, short to ground or short to voltage in MAP sensor input circuit. Ensure MAP sensor input circuit is not shorted to ground circuit. Repair as necessary. After repairs, go to step 11 . If circuit is okay, go to step 10 .
8. Replace MAP sensor. After repairs, go to step 11 .
9. Repair open or high resistance in MAP sensor ground circuit. After repairs, go to step 11 .
10. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
11. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Check for blocked or pinched vacuum hose to MAP sensor. Check MAP sensor filter for damage, blockage, or water and vapor contamination. Check for engine vacuum leaks. A shifted or incorrectly calibrated MAP sensor may cause a DTC P0106 to set. Check for a poor PCM electrical connection.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

PCM uses MAP sensor signals to control fuel delivery and ignition timing. MAP sensor measures changes in intake manifold pressure (vacuum). PCM sends a 5-volt reference voltage to MAP sensor. Changes in pressure, resulting from engine load and RPM, are converted into an output voltage monitored by PCM. As manifold pressure changes, sensor output voltage also changes. See MANIFOLD PRESSURE VS. SCAN TOOL VOLTAGE table. By monitoring sensor output voltage, PCM knows the value of manifold pressure.

MAP sensor is also used to measure barometric pressure, allowing PCM to make adjustments for changes in altitudes. DTC P0106 will set when

1. MAP sensor output voltage is greater than 3.3 volts for more than 10 seconds, throttle valve is closed, and engine speed is less than 1000 RPM.
2. MAP sensor output voltage is less than one volt for more than 5 seconds, TP sensor voltage is at least 1.82 volts, and engine speed is less than 2500 RPM.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and information in freeze frame buffer. PCM will enter Fail-Safe Function using MAP sensor value of 6.8 psi (46.7 kPa).

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Start engine and allow it to reach normal operating temperature. Using scan tool, monitor MAP sensor parameter. If MAP sensor value is 1.0-2.4 volts, go to next step. If voltage is not 1.0-2.4 volts, go to step 4 .
3. Turn ignition on, with engine off. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Operate vehicle within freeze frame conditions. If DTC P0106 resets, go to next step. If DTC P0106 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S21444473012000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
4. Check for damaged, disconnected or misrouted vacuum hoses. Check for a plugged vacuum hose or valve. Check for intake manifold leaks, MAP sensor seal leaks or throttle body leaks. Check for a faulty, missing or incorrectly installed PCV valve. Check for restricted air intake or exhaust system. Repair as necessary. After repairs, go to step 9 . If no problems are found, go to next step.
5. Disconnect MAP sensor electrical connector. Turn ignition on, with engine off. Using DVOM, measure voltage between ground and MAP sensor connector (harness side) input circuit. See WIRING DIAGRAMS article. If voltage is 4.9 volts, go to step 7 . If voltage is not 4.9 volts, go to next step.
6. Check for an open, short to ground or short to voltage in MAP sensor input circuit. Ensure MAP sensor input circuit is not shorted to ground circuit. Repair as necessary. After repairs, go to step 9 . If circuit is okay, go to step 8 .
7. Replace MAP sensor. After repairs, go to step 9 .
8. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
9. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Using scan tool, check MAP sensor parameter for a fixed value, or a slow response when throttle is snapped. Check for an exhaust restriction. A restriction in catalytic converter can cause MAP sensor to be skewed.

An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Manifold Absolute Pressure (MAP) sensor responds to changes in intake manifold pressure (vacuum). PCM applies 5 volts to MAP sensor. Changes in pressure, resulting from engine load and RPM, are converted into a voltage signal monitored by PCM. A low voltage reading at PCM indicates low manifold pressure, and a high voltage at PCM indicates high manifold pressure. DTC P0107 will set when low voltage input at PCM indicates manifold absolute pressure .7 psi (5 kPa) or less for at least .5 second.

When DTC sets, MIL will illuminate. PCM will record operating conditions at time of failure and information in freeze frame buffer. PCM will enter Fail-Safe Function using TP sensor and engine RPM. EGR and EVAP purge control will be stopped.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Turn ignition on, with engine off. Using scan tool, with throttle closed, monitor MAP sensor parameter. If MAP sensor display is .7 psi (5 kPa) or less, go to step 4 . If MAP sensor display is greater than .7 psi (5 kPa), go to next step.
3. Turn ignition on, with engine off. Using scan tool, clear DTCs. Operate vehicle within freeze frame conditions. If MAP sensor display is less than .7 psi (5 kPa), go to next step. If MAP sensor display is greater than .7 psi (5 kPa), go to «DIAGNOSTIC AIDS»(ref-189-S23957029332000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
4. Turn ignition off. Disconnect MAP sensor electrical connector. Turn ignition on, with engine off. Using DVOM, measure voltage between ground and MAP sensor connector (harness side) reference voltage circuit. See WIRING DIAGRAMS article. If voltage is 5 volts, go to next step. If voltage is not 5 volts, go to step 7 .
5. Using DVOM, measure voltage between ground and MAP sensor connector (harness side) input circuit. See WIRING DIAGRAMS article. If voltage is 4.9-5.0 volts, go to next step. If voltage is not 4.9-5.0 volts, go to step 8 .
6. Replace MAP sensor. After repairs, go to step 11 .
7. Check for an open or short to ground in reference voltage circuit between MAP sensor and PCM. Repair as necessary. After repairs, go to step 11 . If circuit is okay, go to step 9 .
8. Check for an open or short to ground in input circuit between MAP sensor and PCM. Repair as necessary. After repairs, go to step 11 . If circuit is okay, go to next step.
9. Check for poor connections at PCM and MAP sensor. Repair as necessary. After repairs, go to step 11 . If connections are okay, go to next step.
10. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
11. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

If DTCs P0107 and P0122 are set together, reference voltage circuit could be open or shorted to ground. Check for a blocked or pinched vacuum hose to MAP sensor. Check MAP sensor filter for damage, blockage, or water and vapor contamination. Check for a poor PCM electrical connection.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Manifold Absolute Pressure (MAP) sensor responds to changes in intake manifold pressure (vacuum). PCM applies 5 volts to MAP sensor. Changes in pressure, resulting from engine load and RPM, are converted into a voltage signal monitored by PCM. A low voltage reading at PCM indicates low manifold pressure, and a high voltage at PCM indicates high manifold pressure. DTC P0108 will set when high voltage input at PCM indicates manifold absolute pressure of 18.9 psi (130 kPa) or more for at least .5 second.

When DTC sets, MIL will illuminate. PCM will record operating conditions at time of failure and information in freeze frame buffer. PCM will enter Fail-Safe Function using TP sensor and engine RPM. EGR and EVAP purge control will be stopped.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Turn ignition on, with engine off. With throttle closed, monitor MAP sensor parameter. If MAP sensor display is 18.9 psi (130 kPa) or more, go to step 4 . If MAP sensor display is less than 18.9 psi (130 kPa), go to next step.
3. Turn ignition on, with engine off. Using scan tool, clear DTCs. Operate vehicle within freeze frame conditions. If MAP sensor display is greater than 18.9 psi (130 kPa), go to next step. If MAP sensor display is 18.9 psi (130 kPa) or less, go to «DIAGNOSTIC AIDS»(ref-189-S39284138302000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
4. Turn ignition off. Disconnect MAP sensor electrical connector. Turn ignition on, with engine off. Using DVOM, measure voltage between ground and MAP sensor connector (harness side) input circuit. See WIRING DIAGRAMS article. If voltage is 4.9-5.0 volts, go to step 7 . If voltage is not 4.9-5.0 volts, go to next step.
5. Check for an open or short to voltage in input circuit between MAP sensor and PCM. Repair as necessary. After repairs, go to step 11 . If circuit is okay, go to next step.
6. Check for poor connections at PCM and MAP sensor. Repair as necessary. After repairs, go to step 11 . If connections are okay, go to step 10 .
7. Using DVOM, measure voltage between MAP sensor connector (harness side) input circuit and ground circuit. See WIRING DIAGRAMS article. If voltage is 4.9-5.0 volts, go to step 9 . If voltage is not 4.9-5.0 volts, go to next step.
8. Check for an open in ground circuit between MAP sensor and PCM. Repair as necessary. After repairs, go to step 11 . If circuit is okay, go to step 10 .
9. Replace MAP sensor. After repairs, go to step 11 .
10. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
11. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

If DTC P0108 is set, check 5-volt reference voltage circuit for a short to voltage. If DTCs P0108, P0113, P0118 and P0123 are set together, check for an open in ground circuit. Check for a leaking vacuum hose to MAP sensor. Check MAP sensor filter for damage, blockage, or water and vapor contamination. Check for a poor PCM electrical connection.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Intake Air Temperature (IAT) sensor is a thermistor (resistance changes as ambient temperature changes) in series with a fixed resistor within PCM. PCM supplies a 5-volt reference voltage to IAT sensor. As temperature changes, IAT sensor resistance changes, which changes voltage.

As intake air temperature decreases, IAT sensor resistance increases. As intake air temperature increases, IAT sensor resistance decreases. PCM monitors voltage input from IAT sensor and converts it into a temperature value. DTC P0110 will set when temperature value is -40°F (-40°C) for at least .5 second, or 284°F (140°C) for at least .5 second.

When DTC sets, MIL will illuminate. PCM will record operating conditions at time of failure and information in freeze frame buffer. PCM will enter Fail-Safe Function and assume intake air temperature is 68°F (20°C).

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Turn ignition on, with engine off. Using scan tool, monitor IAT sensor parameter. If IAT sensor value is 284°F (140°C) or more, go to step 5 . If IAT sensor value is less than 284°F (140°C), go to next step.
3. Using scan tool, monitor IAT sensor parameter. If IAT sensor value is -40°F (-40°C) or less, go to step 7 . If IAT sensor value is greater than -40°F (-40°C), go to next step.
4. Turn ignition on, with engine off. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Operate vehicle within freeze frame conditions. If DTC P0110 resets, go to step 2 . If DTC P0110 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S01075216302000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
5. Turn ignition on, with engine off. Disconnect IAT sensor electrical connector. Using scan tool, monitor IAT sensor parameter. If IAT sensor value is -40°F (-40°C), go to step 13 . If IAT sensor value is not -40°F (-40°C), go to next step.
6. Turn ignition off. Disconnect PCM 16-pin connector. Check for a short to ground in PCM 16-pin connector (harness side) IAT sensor input circuit. See WIRING DIAGRAMS article. Ensure IAT sensor input circuit is not shorted to ground circuit. Repair as necessary. After repairs, go to step 15 . If circuit is okay, go to step 14 .
7. Disconnect IAT sensor electrical connector. Using a fused jumper wire, connect IAT sensor harness connector circuits together. Using scan tool, monitor IAT sensor parameter. If IAT sensor value is 284°F (140°C) or more, go to step 9 . If IAT sensor value is less than 284°F (140°C), go to next step.
8. Using a fused jumper wire, connect IAT sensor harness connector input circuit to ground. See WIRING DIAGRAMS article. Using scan tool, monitor IAT sensor parameter. If IAT sensor value is 284°F (140°C) or more, go to step 10 . If IAT sensor value is less than 284°F (140°C), go to step 11 .
9. Check for poor connections at IAT sensor. Repair as necessary. After repairs, go to step 15 . If connections are okay, go to step 13 .
10. Turn ignition off. Disconnect PCM 16-pin connector. Check for an open in PCM 16-pin connector (harness side) IAT sensor ground circuit. See WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step 15 . If circuit is okay, go to step 12 .
11. Turn ignition off. Disconnect PCM 16-pin connector. Check for an open or short in PCM 16-pin connector (harness side) IAT sensor input circuit. See WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step 15 . If circuit is okay, go to next step.
12. Check for poor connections at PCM. Repair as necessary. After repairs, go to step 15 . If connections are okay, go to step 14 .
13. Replace IAT sensor. After repairs, go to step 15 .
14. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
15. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Check for a poor PCM electrical connection. Check for a shifted IAT sensor. See INTAKE AIR TEMPERATURE (IAT) SENSOR RESISTANCE table. A shifted sensor could result in poor driveability complaints.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

INTAKE AIR TEMPERATURE (IAT) SENSOR RESISTANCE (1)

Intake Air Temperature (IAT) sensor uses a thermistor (a variable resistor) in series with a fixed resistor inside PCM to control signal voltage to PCM. PCM applies 5 volts to IAT sensor. PCM monitors voltage across IAT sensor and converts it into a temperature reading. When outside air temperature is cold, IAT sensor resistance is high. When outside air temperature is warm, IAT sensor resistance is low. DTC P0111 will set when engine is running and IAT sensor signal voltage indicates a smaller change than expected in voltage input during a warm-up cycle.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of diagnostic failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Turn ignition on, with engine off. Allow engine to cool to ambient air temperature. Compare IAT sensor value with ambient air temperature. If IAT sensor value is within 0-9°F (0-5°C) of ambient air temperature, go to next step. If IAT sensor value is not within 0-9°F (0-5°C) of ambient air temperature, go to step 4 .
3. Disconnect IAT sensor electrical connector. Remove IAT sensor from air cleaner assembly. Reconnect IAT sensor electrical connector to IAT sensor. While monitoring IAT sensor parameter on scan tool, wrap a cool damp shop towel around IAT sensor to lower temperature. Remove cool shop towel and replace with a warm shop towel while continuing to monitor IAT sensor parameter. If IAT sensor value skips, jumps or is fixed, go to step 9 . If IAT sensor value does not skip, jump or is not fixed, go to «DIAGNOSTIC AIDS»(ref-189-S24028953882000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
4. Disconnect IAT sensor electrical connector. Using a fused jumper wire, connect IAT sensor harness connector circuits together. If IAT sensor value is 246°F (119°C), go to step 9 . If IAT sensor value is not 246°F (119°C), go to next step.
5. Remove fused jumper wire. Disconnect PCM 16-pin connector. Using DVOM, measure resistance of IAT sensor input circuit between IAT sensor and PCM. See WIRING DIAGRAMS article. If resistance is less than .5 ohm, go to next step. If resistance is .5 ohm or greater, go to step 7 .
6. Using DVOM, measure resistance of IAT sensor ground circuit between IAT sensor and PCM. See WIRING DIAGRAMS article. If resistance is less than .5 ohm, go to step 10 . If resistance is .5 ohm or greater, go to step 8 .
7. Check for a short to ground or high resistance in IAT sensor input circuit between IAT sensor and PCM. Repair as necessary. After repairs, go to step 11 .
8. Check for an open or high resistance in IAT sensor ground circuit between IAT sensor and PCM. Repair as necessary. After repairs, go to step 11 .
9. Replace IAT sensor. After repairs, go to step 11 .
10. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
11. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Check for a poor PCM electrical connection. Check for a shifted IAT sensor. See INTAKE AIR TEMPERATURE (IAT) SENSOR RESISTANCE table. A shifted sensor could result in poor driveability complaints.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Intake Air Temperature (IAT) sensor uses a thermistor (a variable resistor) in series with a fixed resistor inside PCM to control signal voltage to PCM. PCM applies 5 volts to IAT sensor. PCM monitors voltage across IAT sensor and converts it into a temperature reading. When outside air temperature is cold, IAT sensor resistance is high and PCM will receive a high voltage input. When outside air temperature is warm, IAT sensor resistance is low and PCM will receive a low voltage input. DTC P0112 will set when IAT sensor signal voltage indicates an intake air temperature greater than 246°F (119°C) for at least .5 second.

When DTC sets, MIL will illuminate. PCM will record operating conditions at time of failure and information in freeze frame buffer. PCM will enter Fail-Safe Function and assume intake air temperature is 68°F (20°C). EGR control will be stopped.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Turn ignition on, with engine off. Using scan tool, monitor IAT sensor parameter. If IAT sensor value is 246°F (119°C) or more, go to step 4 . If IAT sensor value is less than 246°F (119°C), go to next step.
3. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If DTC P0112 resets, go to next step. If DTC P0112 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S10928989462000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
4. Disconnect IAT sensor electrical connector. Using scan tool, monitor IAT sensor parameter. If IAT sensor value is -40°F (-40°C) or less, go to step 7 . If IAT sensor value is greater than -40°F (-40°C), go to next step.
5. Turn ignition off. Disconnect PCM 16-pin connector. Check for a short to ground in PCM 16-pin connector (harness side) IAT sensor input circuit. See WIRING DIAGRAMS article. If circuit is shorted to ground, go to step 8 . If circuit is okay, go to next step.
6. Check for a short to voltage in PCM 16-pin connector (harness side) IAT sensor ground circuit. See WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step 10 . If circuit is okay, go to step 9 .
7. Replace IAT sensor. After repairs, go to step 10 .
8. Repair IAT sensor input circuit. After repairs, go to step 10 .
9. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
10. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Check for a poor PCM electrical connection. Check for a shifted IAT sensor. See INTAKE AIR TEMPERATURE (IAT) SENSOR RESISTANCE table. A shifted sensor could result in poor driveability complaints.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Intake Air Temperature (IAT) sensor uses a thermistor (a variable resistor) in series with a fixed resistor inside PCM to control signal voltage to PCM. PCM applies 5 volts to IAT sensor. PCM monitors voltage across IAT sensor and converts it into a temperature reading. When outside air temperature is cold, IAT sensor resistance is high and PCM will receive a high voltage input. When outside air temperature is warm, IAT sensor resistance is low and PCM will receive a low voltage input. DTC P0113 will set when IAT sensor signal voltage indicates an intake air temperature less than -40°F (-40°C) for at least .5 second.

When DTC sets, MIL will illuminate. PCM will record operating conditions at time of failure and information in freeze frame buffer. PCM will enter Fail-Safe Function and assume intake air temperature is 68°F (20°C). EGR control will be stopped.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Turn ignition on, with engine off. Using scan tool, monitor IAT sensor parameter. If IAT sensor value is -40°F (-40°C) or less, go to step 4 . If IAT sensor value is greater than -40°F (-40°C), go to next step.
3. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If DTC P0113 resets, go to next step. If DTC P0113 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S22663611972000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
4. Disconnect IAT sensor electrical connector. Using a fused jumper wire, connect IAT sensor harness connector circuits together. Using scan tool, monitor IAT sensor parameter. If IAT sensor value is 246°F (119°C), go to step 6 . If IAT sensor value is not 246°F (119°C), go to next step.
5. Using a fused jumper wire, connect IAT sensor harness connector input circuit to ground. See WIRING DIAGRAMS article. Using scan tool, monitor IAT sensor parameter. If IAT sensor value is 246°F (119°C), go to step 7 . If IAT sensor value is not 246°F (119°C), go to step 8 .
6. Check for poor connections at IAT sensor. Repair as necessary. After repairs, go to step 12 . If connections are okay, go to step 10 .
7. Turn ignition off. Disconnect PCM 16-pin connector. Check for an open in PCM 16-pin connector (harness side) IAT sensor ground circuit. See WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step 12 . If circuit is okay, go to step 9 .
8. Turn ignition off. Disconnect PCM 16-pin connector. Check for an open in PCM 16-pin connector (harness side) IAT sensor input circuit. See WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step 12 . If circuit is okay, go to next step.
9. Check for poor connections at PCM. Repair as necessary. After repairs, go to step 12 . If connections are okay, go to step 11 .
10. Replace IAT sensor. After repairs, go to step 12 .
11. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
12. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

If DTC P0113 is set, check IAT sensor input circuit for a short to voltage. If DTCs P0108, P0113, P0118 and P0123 are set together, check for an open in ground circuit. Check for a poor PCM electrical connection. Check for a shifted IAT sensor. See INTAKE AIR TEMPERATURE (IAT) SENSOR RESISTANCE table. A shifted sensor could result in poor driveability complaints.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Engine Coolant Temperature (ECT) sensor is a thermistor (resistance changes as engine coolant temperature changes) in series with a fixed resistor within PCM. PCM supplies a 5-volt reference voltage to ECT sensor. As temperature changes, ECT sensor resistance changes, which changes voltage.

As engine coolant temperature decreases, ECT sensor resistance increases. As engine coolant temperature increases, ECT sensor resistance decreases. PCM monitors voltage input from ECT sensor and converts it into a temperature value. DTC P0115 will set when temperature value is -40°F (-40°C) for at least .5 second, or 284°F (140°C) for at least .5 second.

When DTC sets, MIL will illuminate. PCM will record operating conditions at time of diagnostic failure and store information in freeze frame buffer. PCM will default to 176°F (80°C).

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Turn ignition on, with engine off. Using scan tool, monitor ECT sensor parameter. If ECT sensor value is 284°F (140°C) or more, go to step 5 . If ECT sensor value is less than 284°F (140°C), go to next step.
3. Using scan tool, monitor ECT sensor parameter. If ECT sensor value is -40°F (-40°C) or less, go to step 7 . If ECT sensor value is greater than -40°F (-40°C), go to next step.
4. Turn ignition on, with engine off. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Operate vehicle within freeze frame conditions. If DTC P0115 resets, go to step 2 . If DTC P0115 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S40022254802000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
5. Turn ignition on, with engine off. Disconnect ECT sensor electrical connector. Using scan tool, monitor ECT sensor parameter. If ECT sensor value is -40°F (-40°C), go to step 13 . If ECT sensor value is not -40°F (-40°C), go to next step.
6. Turn ignition off. Disconnect PCM 16-pin connector. Check for a short to ground in PCM 16-pin connector (harness side) ECT sensor input circuit. Ensure ECT sensor input circuit is not shorted to ground circuit. See WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step 15 . If circuit is okay, go to step 14 .
7. Disconnect ECT sensor electrical connector. Using a fused jumper wire, connect ECT sensor harness connector circuits together. Using scan tool, monitor ECT sensor parameter. If ECT sensor value is 284°F (140°C) or more, go to step 9 . If ECT sensor value is less than 284°F (140°C), go to next step.
8. Using a fused jumper wire, connect ECT sensor harness connector input circuit to ground. See WIRING DIAGRAMS article. Using scan tool, monitor ECT sensor parameter. If ECT sensor value is 284°F (140°C) or more, go to step 10 . If ECT sensor value is less than 284°F (140°C), go to step 11 .
9. Check for poor connections at ECT sensor. Repair as necessary. After repairs, go to step 15 . If connections are okay, go to step 13 .
10. Turn ignition off. Disconnect PCM 16-pin connector. Check for an open in PCM 16-pin connector (harness side) ECT sensor ground circuit. See WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step 15 . If circuit is okay, go to step 12 .
11. Turn ignition off. Disconnect PCM 16-pin connector. Check for an open or short in PCM 16-pin connector (harness side) ECT sensor input circuit. See WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step 15 . If circuit is okay, go to next step.
12. Check for poor connections at PCM. Repair as necessary. After repairs, go to step 15 . If connections are okay, go to step 14 .
13. Replace ECT sensor. After repairs, go to step 15 .
14. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
15. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

If DTCs P0105, P0110, P0115 and P0120 are also set, ECT sensor ground circuit may be at fault. Ensure engine coolant level is full. Check for a shifted ECT sensor. See ENGINE COOLANT TEMPERATURE (ECT) SENSOR RESISTANCE table. A shifted sensor could result in poor driveability complaints.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

ENGINE COOLANT TEMPERATURE (ECT) SENSOR RESISTANCE (1)

Engine Coolant Temperature (ECT) sensor is a thermistor (resistance changes as engine coolant temperature changes) in series with a fixed resistor within PCM. PCM supplies a 5-volt reference voltage to ECT sensor.

As engine coolant temperature decreases, ECT sensor resistance increases. As engine coolant temperature increases, ECT sensor resistance decreases. PCM monitors voltage input from ECT sensor and converts it into a temperature value. DTC P0116 will set when engine coolant temperature (as indicated by ECT sensor) variation is less than expected value, engine has been running for more than 20 minutes and vehicle has been driven faster than 30 MPH at least once since engine start.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of diagnostic failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Using scan tool, check if DTC P0117 or P0118 is set. If DTC P0117 is set, diagnose DTC. See «DTC P0117: ENGINE COOLANT TEMPERATURE (ECT) SENSOR CIRCUIT VOLTAGE LOW (1.0L & 1.3L)»(ref-189-S03876199962000030800000) . If DTC P0118 is set, diagnose DTC. See «DTC P0118: ENGINE COOLANT TEMPERATURE (ECT) SENSOR CIRCUIT VOLTAGE HIGH (1.0L & 1.3L)»(ref-189-S32374857642000030800000) . If DTC P0117 or P0118 is not set, go to next step.
3. Measure actual engine coolant temperature. Turn ignition on, with engine off. Using scan tool, monitor ECT sensor parameter. If scan tool display value is near actual engine coolant temperature, go to step 11 . If scan tool display value is not near actual engine coolant temperature, go to next step.
4. Disconnect ECT sensor electrical connector. Using scan tool, monitor ECT sensor parameter. If ECT sensor value is -40°F (-40°C), go to next step. If ECT sensor value is not -40°F (-40°C), go to step 8 .
5. Using a fused jumper wire, connect ECT sensor input circuit to ground circuit at ECT sensor harness connector. See WIRING DIAGRAMS article. Using scan tool, monitor ECT sensor parameter. If ECT sensor value is 246°F (119°C), go to step 13 . If ECT sensor value is not 246°F (119°C), go to next step.
6. Using a fused jumper wire, connect ECT sensor harness connector input circuit to ground. See WIRING DIAGRAMS article. Using scan tool, monitor ECT sensor parameter. If ECT sensor value is 246°F (119°C), go to next step. If ECT sensor value is not 246°F (119°C), go to step 8 .
7. Repair open or high resistance in ECT sensor ground circuit. After repairs, go to step 14 . If circuit is okay, go to step 9 .
8. Turn ignition off. Disconnect PCM harness connector C2. Check for short or high resistance in ECT sensor input circuit. Repair as necessary. After repairs, go to step 14 . If circuit is okay, go to next step.
9. Check for poor connections at PCM and ECT sensor. Repair as necessary. After repairs, go to step 14 . If circuit is okay, go to next step.
10. Replace PCM. Program PCM using required equipment. After replacing PCM, go to step 14 .
11. Inspect engine cooling system for a faulty thermostat, low coolant level, incorrect coolant, or faulty cooling system operation. Repair as necessary. After repairs, go to step 14 . If cooling system is okay, go to next step.
12. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Operate vehicle within freeze frame conditions to set DTC P0116. If DTC P0116 resets, go to next step. If DTC P0116 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S42753258662000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
13. Replace ECT sensor. After repairs, go to next step.
14. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

If DTCs P0106 and P0121 are also set, ECT sensor ground circuit may be at fault. Ensure engine coolant level is full. Check for a faulty thermostat. Check for a shifted ECT sensor. See ENGINE COOLANT TEMPERATURE (ECT) SENSOR RESISTANCE table. A shifted sensor could result in poor driveability complaints.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Engine Coolant Temperature (ECT) sensor is a thermistor (resistance changes as engine coolant temperature changes) in series with a fixed resistor within PCM. PCM supplies a 5-volt reference voltage to ECT sensor.

As engine coolant temperature decreases, ECT sensor resistance increases. As engine coolant temperature increases, ECT sensor resistance decreases. PCM monitors voltage input from ECT sensor and converts it into a temperature value. DTC P0116 will set when

1. Engine coolant temperature is less than 20°F (-6.7°C) at start up, and ECT sensor value is 95°F (35°C) or less after engine has been running for more than 20 minutes.
2. Engine coolant temperature is 20-50°F (-6.7-10°C) at start up, and ECT sensor value is 95°F (35°C) or less after engine has been running for 5 minutes or more.
3. Engine coolant temperature is greater than 50°F (10°C) at start up, and ECT sensor value is 95°F (35°C) or less after engine has been running for 2 minutes or more.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of diagnostic failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Using scan tool, check if DTC P0115 is set. If DTC P0115 is set, diagnose DTC. See «DTC P0115: ENGINE COOLANT TEMPERATURE (ECT) SENSOR CIRCUIT (1.8L)»(ref-189-S25031211182000030800000) . If DTC P0115 is not set, go to next step.
3. Measure actual engine coolant temperature. Turn ignition on, with engine off. Using scan tool, monitor ECT sensor parameter. If scan tool display value is near actual engine coolant temperature, go to step 11 . If scan tool display value is not near actual engine coolant temperature, go to next step.
4. Disconnect ECT sensor electrical connector. Using scan tool, monitor ECT sensor parameter. If ECT sensor value is -40°F (-40°C), go to next step. If ECT sensor value is not -40°F (-40°C), go to step 8 .
5. Using a fused jumper wire, connect ECT sensor input circuit to ground circuit at ECT sensor harness connector. See WIRING DIAGRAMS article. Using scan tool, monitor ECT sensor parameter. If ECT sensor value is 284°F (140°C), go to step 13 . If ECT sensor value is not 284°F (140°C), go to next step.
6. Using a fused jumper wire, connect ECT sensor harness connector input circuit to ground. See WIRING DIAGRAMS article. Using scan tool, monitor ECT sensor parameter. If ECT sensor value is 284°F (140°C), go to next step. If ECT sensor value is not 284°F (140°C), go to step 8 .
7. Repair open or high resistance in ECT sensor ground circuit. After repairs, go to step 14 . If circuit is okay, go to step 9 .
8. Turn ignition off. Disconnect PCM harness connector C2. Check for short or high resistance in ECT sensor input circuit. Repair as necessary. After repairs, go to step 14 . If circuit is okay, go to next step.
9. Check for poor connections at ECT sensor and PCM. Repair as necessary. After repairs, go to step 14 . If connections are okay, go to next step.
10. Replace PCM. Program PCM using required equipment. After replacing PCM, go to step 14 .
11. Inspect engine cooling system for a faulty thermostat, low coolant level, incorrect coolant, or faulty cooling system operation. Repair as necessary. After repairs, go to step 14 . If cooling system is okay, go to next step.
12. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Operate vehicle within freeze frame conditions to set DTC P0116. If DTC P0116 resets, go to next step. If DTC P0116 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S34224575292000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
13. Replace ECT sensor. After repairs, go to next step.
14. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

If DTCs P0115 and P0116 are both set, ECT sensor circuit may be open. Diagnose P0115 first. If DTCs P0105, P0110, P0115 and P0120 are also set, ECT sensor ground circuit may be at fault. Ensure engine coolant level is full. Check for a shifted ECT sensor. See ENGINE COOLANT TEMPERATURE (ECT) SENSOR RESISTANCE table. A shifted sensor could result in poor driveability complaints.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Engine Coolant Temperature (ECT) sensor uses a thermistor (a variable resistor) in series with a fixed resistor inside PCM to control signal voltage to PCM. PCM applies 5 volts to ECT sensor. PCM monitors voltage across ECT sensor and converts it into a temperature reading. When engine coolant temperature is cold, ECT sensor resistance is high and PCM will receive a high voltage input. When engine coolant temperature is warm, ECT sensor resistance is low and PCM will receive a low voltage input. DTC P0117 will set when ECT sensor signal voltage indicates an engine coolant temperature greater than 246°F (119°C) for at least .5 second with engine running.

When DTC sets, MIL will illuminate. PCM will record operating conditions at time of failure and store information in freeze frame buffer. PCM will enter Fail-Safe Function and assume engine coolant temperature is 176°F (80°C). EGR, ISC and A/C control will be stopped. PCM will turn on engine cooling fan.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Turn ignition on, with engine off. Using scan tool, monitor ECT sensor parameter. If ECT sensor value is 246°F (119°C) or more, go to step 4 . If ECT sensor value is less than 246°F (119°C), go to next step.
3. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If DTC P0117 resets, go to next step. If DTC P0117 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S07786517042000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
4. Disconnect ECT sensor electrical connector. Using scan tool, monitor ECT sensor parameter. If ECT sensor value is -40°F (-40°C) or less, go to step 7 . If ECT sensor value is greater than -40°F (-40°C), go to next step.
5. Turn ignition off. Disconnect PCM 16-pin connector. Check for a short to ground in PCM 16-pin connector (harness side) ECT sensor input circuit. See WIRING DIAGRAMS article. If circuit is shorted to ground, go to step 8 . If circuit is okay, go to next step.
6. Check for a short to voltage in PCM 16-pin connector (harness side) ECT sensor ground circuit. See WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step 10 . If circuit is okay, go to step 9 .
7. Replace ECT sensor. After repairs, go to step 10 .
8. Repair ECT sensor input circuit. After repairs, go to step 10 .
9. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
10. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

After engine is started, ECT sensor should rise steadily to about 203°F (95°C) and stabilize when thermostat opens. Ensure engine is not overheating and has not been subjected to conditions which would create an overheating condition (i.e., overload, trailer towing, hilly terrain, heavy stop and go traffic, etc.). Check for a shifted ECT sensor. See ENGINE COOLANT TEMPERATURE (ECT) SENSOR RESISTANCE table. A shifted sensor could result in poor driveability complaints.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Engine Coolant Temperature (ECT) sensor uses a thermistor (a variable resistor) in series with a fixed resistor inside PCM to control signal voltage to PCM. PCM applies 5 volts to ECT sensor. PCM monitors voltage across ECT sensor and converts it into a temperature reading. When engine coolant temperature is cold, ECT sensor resistance is high and PCM will receive a high voltage input. When engine coolant temperature is warm, ECT sensor resistance is low and PCM will receive a low voltage input. DTC P0118 will set when ECT sensor signal voltage indicates an engine coolant temperature less than -40°F (-40°C) for at least 5 seconds with engine running.

When DTC sets, MIL will illuminate. PCM will record operating conditions at time of failure and store information in freeze frame buffer. PCM will enter Fail-Safe Function and assume engine coolant temperature is 176°F (80°C). EGR, ISC and A/C control will be stopped. PCM will turn on engine cooling fan.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Turn ignition on, with engine off. Using scan tool, monitor ECT sensor parameter. If ECT sensor value is -40°F (-40°C) or less, go to step 4 . If ECT sensor value is greater than -40°F (-40°C), go to next step.
3. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If DTC P0118 resets, go to next step. If DTC P0118 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S00199864852000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
4. Disconnect ECT sensor electrical connector. Using a fused jumper wire, connect ECT sensor harness connector circuits together. Using scan tool, monitor ECT sensor parameter. If ECT sensor value is 246°F (119°C), go to step 6 . If ECT sensor value is not 246°F (119°C), go to next step.
5. Using a fused jumper wire, connect ECT sensor harness connector input circuit to ground. See WIRING DIAGRAMS article. Using scan tool, monitor ECT sensor parameter. If ECT sensor value is 246°F (119°C), go to step 7 . If ECT sensor value is not 246°F (119°C), go to step 8 .
6. Check for poor connections at ECT sensor. Repair as necessary. After repairs, go to step 12 . If connections are okay, go to step 10 .
7. Turn ignition off. Disconnect PCM 16-pin connector. Check for an open in PCM 16-pin connector (harness side) ECT sensor ground circuit. See WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step 12 . If circuit is okay, go to step 9 .
8. Turn ignition off. Disconnect PCM 16-pin connector. Check for an open in PCM 16-pin connector (harness side) ECT sensor input circuit. See WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step 12 . If circuit is okay, go to next step.
9. Check for poor connections at PCM. Repair as necessary. After repairs, go to step 12 . If connections are okay, go to step 11 .
10. Replace ECT sensor. After repairs, go to step 12 .
11. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
12. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Cooling fan will turn on when DTC P0118 sets. If DTC P0118 is set, check ECT sensor input circuit for a short to voltage.

Check for a poor PCM electrical connection. After engine is started, ECT sensor should rise steadily to about 203°F (95°C) and stabilize when thermostat opens. Ensure engine is not overheating and has not been subjected to conditions which would create an overheating condition (i.e., overload, trailer towing, hilly terrain, heavy stop and go traffic, etc.). Check for a shifted ECT sensor. See ENGINE COOLANT TEMPERATURE (ECT) SENSOR RESISTANCE table. A shifted sensor could result in poor driveability complaints.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Throttle Position (TP) sensor is mounted on throttle body and detects throttle opening angle. When throttle valve is fully closed, at engine idle, about 0.3-0.8 volt is applied to TP sensor input circuit. Voltage will increase in proportion to amount of throttle valve opening angle. At Wide Open Throttle (WOT), TP sensor input circuit voltage is about 3.2-4.9 volts. PCM determines vehicle driving condition from TP sensor input and calculate air-fuel ratio correction, power increase correction and fuel-cut control. DTC P0120 will set when

1. TP sensor input to PCM is less than 0.1 volt and throttle valve is in closed position.
2. TP sensor input to PCM is greater than 4.9 volts and throttle valve is at WOT position.

When DTC sets, MIL will illuminate. PCM will record operating conditions at time of failure and store information in freeze frame buffer. TP sensor angle will default to zero percent.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Turn ignition on, with engine off. With throttle closed, monitor TP sensor parameter. If TP sensor value is greater than 25 percent, go to step 5 . If TP sensor value is 25 percent or less, go to next step.
3. Observe TP sensor with throttle closed. If TP sensor value is less than 6 percent, go to step 12 . If TP sensor value is 6 percent or greater, go to next step.
4. Turn ignition on, with engine off. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Operate vehicle within freeze frame conditions. If DTC P0120 resets, go to step 2 . If DTC P0120 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S34758939312000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
5. Turn ignition off. Disconnect TP sensor electrical connector. Turn ignition on, with engine off. Using scan tool, observe TP sensor parameter. If TP sensor value is greater than zero percent, go to step 7 . If TP sensor value is zero percent, go to next step.
6. Using test light connected to battery voltage, probe TP sensor connector (harness side) ground circuit. See WIRING DIAGRAMS article. If test light illuminates, go to step 8 . If test light does not illuminate, go to step 10 .
7. Turn ignition off. Disconnect PCM 16-pin connector. Turn ignition on, with engine off. Check for a short to voltage in PCM 16-pin connector TP sensor input circuit. See WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step 21 . If circuit is okay, go to step 20 .
8. Turn ignition on, with engine off. Using DVOM, measure voltage at TP sensor connector (harness side) reference voltage circuit. See WIRING DIAGRAMS article. If voltage is 5 volts, go to next step. If voltage is not 5 volts, go to step 11 .
9. Check for poor connections at PCM and TP sensor. Repair as necessary. After repairs, go to step 21 . If connections are okay, go to step 18 .
10. Turn ignition off. Disconnect PCM 16-pin connector. Check for an open in PCM 16-pin connector TP sensor ground circuit. See WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step 21 . If circuit is okay, go to step 20 .
11. Turn ignition off. Disconnect PCM 16-pin connector. Check for an open or short in PCM 16-pin connector TP sensor reference voltage circuit. See WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step 21 . If circuit is okay, go to step 20 .
12. Disconnect TP sensor electrical connector. Using a fused jumper wire, connect TP sensor harness connector reference voltage and input circuits together. See WIRING DIAGRAMS article. Using scan tool, monitor TP sensor parameter. If TP sensor value is greater than 90 percent, go to step 18 . If TP sensor value is 90 percent or less, go to next step.
13. Connect a test light between battery voltage and TP sensor harness connector input circuit. See WIRING DIAGRAMS article. Using scan tool, monitor TP sensor parameter. If TP sensor value is greater than 90 percent, go to next step. If TP sensor value is 90 percent or less, go to step 16 .
14. Turn ignition off. Disconnect PCM 16-pin connector. Check for an open or short in PCM 16-pin connector TP sensor reference voltage circuit. See WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step 21 . If circuit is okay, go to next step.
15. Check for poor connections at PCM and TP sensor. Repair as necessary. After repairs, go to step 21 . If connections are okay, go to step 20 .
16. Turn ignition off. Disconnect PCM 16-pin connector. Check for an open or short to ground in PCM 16-pin connector TP sensor input circuit. See WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step 21 . If circuit is okay, go to next step.
17. Check for poor connections at PCM. Repair as necessary. After repairs, go to step 21 . If connections are okay, go to step 20 .
18. Check for poor connections at TP sensor. Repair as necessary. After repairs, go to step 21 . If connections are okay, go to next step.
19. Replace TP sensor. After repairs, go to step 21 .
20. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
21. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

An open in idle input circuit will not cause DTC P0120 or P0121 to set. If DTCs P0110, P0115 and P0120 are also set, sensor ground circuit may be at fault.

An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Throttle Position (TP) sensor is a potentiometer whose resistance changes along with throttle valve position. PCM provides a 5-volt reference voltage to TP sensor. PCM reads voltage across sensor and converts it into a reference for throttle position. When TP sensor resistance decreases, throttle valve opening is increasing to Wide Open Throttle (WOT) and voltage being monitored at PCM increases. When TP sensor resistance increases, throttle valve opening is decreasing to idle and voltage being monitored at PCM decreases.

DTC P0121 will set when

1. Engine speed is 1600-3000 RPM.
2. Coolant temperature is greater than 158°F (70°C).
3. Intake air temperature is 14-158°F (-10-70°C).
4. Fuel level is greater than 25 percent.
5. Barometric pressure is greater than 11 psi (75 kPa).
6. MAP change is less than 1.9 psi (13 kPa) per 16 firing events.
7. Difference between expected TP sensor and actual input is greater than 20 degrees.
8. Conditions are present for at least 3 seconds.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of diagnostic failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Ensure engine is at normal operating temperature. Turn ignition on, with engine off. Connect scan tool to DLC. Using scan tool, monitor TP sensor voltage parameter. If TP sensor value is 0.2-1.0 volt with throttle at idle position, and 3.0-4.8 volts at WOT, go to «DIAGNOSTIC AIDS»(ref-189-S35232871672000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article. If voltage is not as specified, go to next step.
3. Disconnect TP sensor electrical connector. Using DVOM connected to ground, backprobe PCM 16-pin connector TP sensor input circuit. See WIRING DIAGRAMS article. If voltage is 4-5 volts, go to next step. If voltage is not 4-5 volts, go to step 5 .
4. Using DVOM, measure voltage of TP sensor input circuit at TP sensor connector (harness side) to ground. See WIRING DIAGRAMS article. If voltage is 4-5 volts, go to step 7 . If voltage is not 4-5 volts, go to step 6 .
5. Check for high resistance, short to voltage or short to ground in TP sensor input circuit. Check TP sensor ground circuit for a poor connection. Repair as necessary. After repairs, go to step 9 . If circuits are okay, go to step 8 .
6. Check for an open in TP sensor input circuit between TP sensor and PCM. Repair as necessary. After repairs, go to step 9 . If circuit is okay, go to step 8 .
7. Replace TP sensor. After repairs, go to step 9 .
8. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
9. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Before replacing TP sensor ensure resistance between TP sensor reference voltage and ground circuits is 2500-6000 ohms, and resistance between TP sensor input and ground circuits is 100-20,000 ohms. Check for a poor PCM electrical connection.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Throttle Position (TP) sensor is mounted on throttle body and detects throttle opening angle. When throttle valve is fully closed, at engine idle, about 0.3-0.8 volt is applied to TP input circuit. Voltage will increase in proportion to amount of throttle valve opening angle. At Wide Open Throttle (WOT), TP input circuit voltage is about 3.2-4.9 volts. PCM determines vehicle driving condition from TP sensor input and calculates air-fuel ratio correction, power increase correction and fuel-cut control. DTC P0121 will set when vehicle speed exceeds 19 MPH, and TP sensor output value is out of applicable range.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of diagnostic failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Turn ignition on, with engine off. Using scan tool, monitor TP sensor angle parameter. Monitor scan tool while depressing accelerator pedal several times. If TP sensor value varies steadily between 10 percent (released position) and 80 percent (depressed position), go to next step. If TP sensor value is not as specified, or reading is erratic, go to step 4 .
3. Turn ignition on, with engine off. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Operate vehicle within freeze frame conditions. If DTC P0121 resets, go to next step. If DTC P0121 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S12073302362000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
4. Disconnect TP sensor electrical connector. Using scan tool, monitor TP sensor angle. If TP sensor value is greater than zero percent, go to step 6 . If TP sensor value is zero percent, go to next step.
5. Connect a test light between TP sensor connector (harness side) reference voltage circuit and TP sensor input circuit. See WIRING DIAGRAMS article. Using scan tool, monitor TP sensor angle. If TP sensor value is greater than 90 percent, go to step 8 . If TP sensor value is 90 percent or less, go to step 7 .
6. Check for a short to battery voltage in TP sensor input circuit. Check for an open in TP sensor ground circuit between TP sensor and PCM. Check TP sensor electrical connector for proper connection. Repair as necessary. After repairs, go to step 10 . If circuits and connection are okay, go to step 9 .
7. Check for an open or short in TP sensor input circuit. Check for high resistance in reference voltage circuit between TP sensor and PCM. Repair as necessary. After repairs, go to step 10 . If circuits are okay, go to step 9 .
8. Replace TP sensor. After repairs, go to step 10 .
9. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
10. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Inspect throttle valve linkage and lever assembly for free and normal movement. A binding or misaligned throttle valve can affect TP sensor input. Ensure throttle lever has not been tampered with. Ensure throttle valve opens fully and the lever contacts the throttle stop. Scan tool typically displays TP angle of 8-10 percent at idle, to 76-77 percent at WOT.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Throttle Position (TP) sensor is a potentiometer whose resistance changes along with throttle valve position. PCM provides a 5-volt reference voltage to TP sensor. PCM reads voltage across sensor and converts it into a reference for throttle position. When TP sensor resistance decreases, throttle valve opening is increasing to Wide Open Throttle (WOT) and voltage being monitored at PCM increases. When TP sensor resistance increases, throttle valve opening is decreasing to idle and voltage being monitored at PCM decreases. DTC P0122 will set when a low voltage input (throttle opening is less than 2 percent) is indicated at PCM with engine running for at least .5 second.

When DTC sets, MIL will illuminate. PCM will record operating conditions at time of diagnostic failure and store information in freeze frame buffer. PCM will enter Fail-Safe Function and assume throttle angle is 20 degrees while stopping ISC control.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Ensure engine is at normal operating temperature. Connect scan tool to DLC. Turn ignition on, with engine off. With throttle closed, monitor TP sensor angle parameter on scan tool. If TP sensor angle parameter is 2 percent or less, go to step 4 . If TP sensor angle parameter is greater than 2 percent, go to next step.
3. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If TP sensor angle parameter is 2 percent or less, go to next step. If TP sensor angle parameter is greater than 2 percent, go to «DIAGNOSTIC AIDS»(ref-189-S39435455102000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
4. Disconnect TP sensor electrical connector. Using DVOM, measure voltage of TP sensor input circuit at TP sensor connector (harness side) to ground. See WIRING DIAGRAMS article. If voltage is 4-5 volts, go to next step. If voltage is not 4-5 volts, go to step 7 .
5. Using DVOM, measure voltage of TP sensor connector (harness side) reference voltage circuit to ground. See WIRING DIAGRAMS article. If voltage is 5 volts, go to step 10 . If voltage is not 5 volts, go to next step.
6. Turn ignition off. Disconnect PCM 16-pin connector. Check for an open in PCM 16-pin connector TP sensor reference voltage circuit. See WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step 12 . If circuit is okay, go to step 8 .
7. Turn ignition off. Disconnect PCM 16-pin connector. Check for a short to ground in PCM 16-pin connector TP sensor input circuit. See WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step 12 . If circuit is okay, go to step 9 .
8. Check for poor connections at reference voltage circuit of PCM or TP sensor. Repair as necessary. After repairs, go to step 12 . If connections are okay, go to step 11 .
9. Check for poor connections at TP sensor input circuit of PCM or TP sensor. Repair as necessary. After repairs, go to step 12 . If connections are okay, go to step 11 .
10. Adjust or replace TP sensor. After repairs, go to step 12 .
11. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
12. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

A misadjusted TP sensor, or a binding or stuck throttle plate could cause DTC to set. See THROTTLE POSITION (TP) SENSOR in appropriate ON-VEHICLE ADJUSTMENTS article. Before replacing TP sensor, ensure resistance between TP sensor reference voltage and ground circuits is 2870-5330 ohms, and resistance between TP sensor input and ground circuits is 100-20,000 ohms. Check for a poor PCM electrical connection. If DTCs P0107 and P0122 are set together, check for an open in reference voltage circuit.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Throttle Position (TP) sensor is a potentiometer whose resistance changes along with throttle valve position. PCM provides a 5-volt reference voltage to TP sensor. PCM reads voltage across sensor and converts it into a reference for throttle position. When TP sensor resistance decreases, throttle valve opening is increasing to Wide Open Throttle (WOT) and voltage being monitored at PCM increases. When TP sensor resistance increases, throttle valve opening is decreasing to idle and voltage being monitored at PCM decreases. DTC P0123 will set when a high voltage input (throttle opening is greater than 96 percent) is indicated at PCM with engine running for at least .5 seconds.

When DTC sets, MIL will illuminate. PCM will record operating conditions at time of diagnostic failure and store information in freeze frame buffer. PCM will enter Fail-Safe Function and assume throttle angle is 20 degrees while stopping ISC control.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Turn ignition on, with engine off. Using scan tool, monitor TP sensor angle parameter while opening throttle valve from closed throttle to Wide Open Throttle (WOT). If TP sensor value is 96 percent or more, go to step 4 . If TP sensor value is less than 96 percent, go to next step.
3. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If TP sensor value is 96 percent or more, go to next step. If TP sensor percentage is less than 96 percent, go to «DIAGNOSTIC AIDS»(ref-189-S29674732422000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
4. Disconnect TP sensor electrical connector. Using DVOM, measure voltage of TP sensor input circuit at TP sensor connector (harness side) to ground. See WIRING DIAGRAMS article. If voltage is 4-5 volts, go to next step. If voltage is not 4-5 volts, go to step 7 .
5. Using DVOM, measure voltage of TP sensor connector (harness side) reference voltage circuit to ground. See WIRING DIAGRAMS article. If voltage is 5 volts, go to next step. If voltage is not 5 volts, go to step 8 .
6. Using test light connected to battery voltage, probe TP sensor connector (harness side) ground circuit. See WIRING DIAGRAMS article. If test light illuminates, go to step 9 . If test light does not illuminate, go to step 10 .
7. Turn ignition off. Disconnect PCM 16-pin connector. Turn ignition on, with engine off. Check for an open or short to voltage in TP sensor input circuit. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to step 12 .
8. Turn ignition off. Disconnect PCM 16-pin connector. Turn ignition on, with engine off. Check for an open or short to voltage in TP sensor reference voltage circuit. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to step 12 .
9. Check for a short to reference voltage circuit in TP sensor input circuit. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to step 11 .
10. Turn ignition off. Disconnect PCM 16-pin connector. Check for an open or poor connection in TP sensor ground circuit. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to step 12 .
11. Adjust or replace TP sensor. After repairs, go to step 13 .
12. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
13. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

A misadjusted TP sensor, or a binding or stuck throttle plate could cause DTC to set. See THROTTLE POSITION (TP) SENSOR in appropriate ON-VEHICLE ADJUSTMENTS article. Before replacing TP sensor, ensure resistance between TP sensor reference voltage and ground circuits is 2870-5330 ohms, and resistance between TP sensor input and ground circuits is 100-20,000 ohms. Check for a poor PCM electrical connection. If DTCs P0108, P0113, P0118 and P0123 are set together, check for an open in ground circuit.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

When engine is first started, engine fuel control system operates in open loop. Air/fuel ratio is determined by inputs from Engine Coolant Temperature (ECT), Throttle Position (TP) and Manifold Absolute Pressure (MAP) sensors. PCM will begin using input from HO2S(s) to control fuel delivery (closed loop operation) when engine obtains normal operating temperature.

DTC P0125 will set when

1. Fuel level is greater than 25 percent.
2. Intake air temperature is 14-122°F (-10-50°C)
3. Barometric pressure is greater than 11 psi (75 kPa).
4. HO2S-1 output varies, indicating sensor is not hot enough to operate properly.
5. Engine temperature required for closed loop operation is not reached within a predetermined amount of time.
6. Diagnostic runs only once per drive cycle.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Allow engine to cool to ambient temperature. Connect scan tool to DLC. Turn ignition on, with engine off. Using scan tool, compare ECT sensor temperature to IAT sensor temperature parameter. If temperature readings are close, go to next step. If temperature readings are not close, go to «DIAGNOSTIC AIDS»(ref-189-S11516619322000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
3. Start engine and allow to idle. Using scan tool, monitor ECT sensor parameter. If ECT sensor value increases to greater than 104°F (40°C) within 10 minutes, go to «DIAGNOSTIC AIDS»(ref-189-S11516619322000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article. If ECT sensor value does not increase as specified, go to next step.
4. If any ECT sensor DTCs are set, diagnose DTC(s). If ECT sensor DTCs are not set, go to next step.
5. Check coolant level and fill as necessary. If coolant was added to cooling system, go to step 10 . If coolant level was okay, go to next step.
6. Using scan tool, compare ECT temperature parameter with actual coolant temperature measured with a thermometer. If temperature readings are close, go to step 8 . If temperature readings are not close, go to next step.
7. Check for high resistance in ECT sensor wiring. Check for poor connections at ECT sensor and PCM. Repair as necessary. After repairs, go to step 10 . If circuits and connections are okay, go to step 9 .
8. Check cooling system. Repair as necessary. After repairs, go to step 10 .
9. Replace ECT sensor. Using scan tool, recheck ECT display. After repairs, go to next step.
10. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Ensure thermostat is operating properly. A stuck-open thermostat may keep engine from reaching normal operating temperature. Check for a poor PCM electrical connection. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

A DTC P0125 could indicate a skewed ECT sensor. Using a scan tool and a thermometer, compare engine coolant temperature displayed on scan tool with actual coolant temperature. Replace ECT sensor if displayed coolant temperature is very different from actual temperature.

HO2S-1 produces a voltage that varies between 100-900 millivolts under normal operating conditions. PCM monitors this voltage and determines if exhaust is lean or rich. If voltage input at PCM is about 100 millivolts, exhaust is lean. If voltage input at PCM is about 900 millivolts, exhaust is rich. PCM constantly monitors HO2S-1 signal during closed loop operation and compensates for a lean or rich condition by adjusting injector pulse width as necessary.

DTC P0125 will set when engine is at normal operating temperature, and HO2S-1 output does not indicate RICH with engine speed at 1400 RPM or more, vehicle speed at 25-62 MPH, throttle valve position is open, and engine has been running for at least 180 seconds.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Start engine and allow it to reach normal operating temperature. Using scan tool, monitor HO2S-1 parameter. Snap throttle and monitor HO2S-1 voltage. If voltage varies within 200-900 millivolts, go to next step. If voltage does not vary within 200-900 millivolts, go to step 4 .
3. Turn ignition on, with engine off. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Operate vehicle within freeze frame conditions. If DTC P0125 resets, go to next step. If DTC P0125 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S26074716852000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
4. Disconnect HO2S-1 electrical connector. Turn ignition on, with engine off. Set DVOM to DC volt scale. Connect DVOM positive lead to battery voltage. Connect negative lead to HO2S-1 connector (harness side) HO2S-1 input circuit. See WIRING DIAGRAMS article. Using scan tool, monitor HO2S-1 parameter. If scan tool voltage is greater than 1155 millivolts, go to next step. If scan tool voltage is 1155 millivolts or less, go to step 6 .
5. Using test light connected to battery voltage, probe HO2S-1 connector (harness side) HO2S-1 ground circuit. See WIRING DIAGRAMS article. If test light illuminates, go to step 8 . If test light does not illuminate, go to step 7 .
6. Check for an open or short in HO2S-1 input circuit between HO2S-1 and PCM. Repair as necessary. After repairs, go to step 10 . If circuit is okay, go to step 9 .
7. Repair open in HO2S-1 ground circuit between HO2S-1 and ground connection. Repair as necessary. After repairs, go to step 10 .
8. Replace HO2S-1. After repairs, go to step 10 .
9. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
10. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Ensure HO2S-1 pigtail is not in contact with exhaust system. Ensure PCM-to-engine grounds are okay. Ensure fuel pressure is correct. If fuel pressure is too low, system will go lean and DTC P0125 may be set. Check for lean fuel injector(s). Check for disconnected or damaged vacuum hoses. Check for vacuum leaks at intake manifold, throttle body, and crankcase ventilation system. Check for exhaust leaks near HO2S-1 that can cause faulty HO2S-1 readings and set DTC P0125. Check for fuel contamination from water or excessive alcohol. Before replacing HO2S-1 because of contamination, determine cause of contamination and repair as necessary.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

HO2S-1 produces a voltage that varies between 100-900 millivolts under normal operating conditions. PCM monitors this voltage and determines if exhaust is lean or rich. If voltage input at PCM is about 100 millivolts, exhaust is lean. If voltage input at PCM is about 900 millivolts, exhaust is rich. PCM constantly monitors HO2S-1 signal during closed loop operation and compensates for a lean or rich condition by adjusting injector pulse width as necessary.

DTC P0130 will set when with engine at idle and at normal operating temperature, HO2S-1 maximum voltage average is more than .40 volt, or minimum voltage average is less than .55 volt.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Start engine and allow it to reach normal operating temperature. Using scan tool, monitor HO2S-1 parameter. Snap throttle and monitor HO2S-1 voltage. If voltage varies within 200-900 millivolts, go to next step. If voltage does not vary within 200-900 millivolts, go to step 4 .
3. Turn ignition on, with engine off. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Operate vehicle within freeze frame conditions. If DTC P0130 resets, go to next step. If DTC P0130 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S33747413082000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
4. Disconnect HO2S-1 electrical connector. Turn ignition on, with engine off. Set DVOM to DC volt scale. Connect DVOM positive lead to battery voltage. Connect negative lead to HO2S-1 connector (harness side) HO2S-1 input circuit. See WIRING DIAGRAMS article. Using scan tool, monitor HO2S-1 parameter. If scan tool voltage is greater than 1155 millivolts, go to next step. If scan tool voltage is less than 1155 millivolts, go to step 6 .
5. Using test light connected to battery voltage, probe HO2S-1 connector (harness side) HO2S-1 ground circuit. See WIRING DIAGRAMS article. If test light illuminates, go to step 8 . If test light does not illuminate, go to step 7 .
6. Check for an open or short in HO2S-1 input circuit between HO2S-1 and PCM. Repair as necessary. After repairs, go to step 10 . If circuit is okay, go to step 9 .
7. Repair open in HO2S-1 ground circuit between HO2S-1 and ground connection. Repair as necessary. After repairs, go to step 10 .
8. Replace HO2S-1. After repairs, go to step 10 .
9. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
10. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Ensure HO2S-1 pigtail is not in contact with exhaust system. Ensure PCM-to-engine grounds are okay. Ensure fuel pressure is correct. If fuel pressure is too low, system will go lean and DTC P0130 may be set. Check for lean fuel injector(s). Check for disconnected or damaged vacuum hoses. Check for vacuum leaks at intake manifold, throttle body, and crankcase ventilation system. Check for exhaust leaks near HO2S-1 that can cause faulty HO2S-1 readings and set DTC P0130.

HO2S-1 contaminated with water could cause a shorted sensor. This occurs more often during wet driving conditions. Silicon contamination of HO2S-1 can cause a low voltage signal. Silicon contamination is indicated by a powdery White deposit on portion of sensor exposed to exhaust stream. Check for fuel contamination from water or excessive alcohol. Check for fuel contamination from water or excessive alcohol. Before replacing HO2S-1 because of contamination, determine cause of contamination and repair as necessary. Check for a saturated EVAP canister or faulty EVAP purge control.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

HO2S-1 produces a voltage that varies between 100-900 millivolts under normal operating conditions. PCM monitors this voltage and determines if exhaust is lean or rich. If voltage input at PCM is about 100 millivolts, exhaust is lean. If voltage input at PCM is about 900 millivolts, exhaust is rich. PCM constantly monitors HO2S-1 signal during closed loop operation and compensates for a lean or rich condition by adjusting injector pulse width as necessary.

DTC P0131 will set when

1. Intake air temperature is 14-158°F (-10-70°C).
2. Barometric pressure is greater than 11 psi (75 kPa).
3. Vehicle speed is greater than 30 MPH for 2 minutes, and then idled for 2 minutes.
4. Engine is operating in closed loop.
5. Maximum HO2S-1 voltage is less than 300 millivolts.
6. HO2S-1 voltage remains excessively low for an extended period of time.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer. PCM will enter Fail-Safe Function and EVAP purge control will be stopped.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. If other HO2S-1 DTCs than P0131 and P0132 are set, diagnose DTC(s). If no other HO2S-1 DTCs are set, go to next step.
3. Start engine and allow it to reach normal operating temperature. Increase engine speed to 2000 RPM for one minute. Operate vehicle within conditions required for DTC to set. Using scan tool, monitor HO2S-1 voltage. If voltage decreases to less than 300 millivolts and increases to greater than 600 millivolts, go to next step. If voltage is not as specified, go to step 5 .
4. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If voltage decreases to less than 300 millivolts and increases to greater than 600 millivolts, go to «DIAGNOSTIC AIDS»(ref-189-S21305166762000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article. If voltage is not as specified, go to next step.
5. Disconnect HO2S-1 electrical connector. Using scan tool, monitor HO2S-1 parameter. If HO2S-1 voltage is 0-35 millivolts, go to next step. If HO2S-1 voltage is not 0-35 millivolts, go to step 10 .
6. Using test light connected to battery voltage, probe HO2S-1 connector (harness side) HO2S-1 ground circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 8 .
7. Using DVOM, check HO2S-1 signal voltage. Set DVOM to DC volt scale. Connect DVOM positive lead to battery voltage. Connect negative lead to HO2S-1 connector (harness side) HO2S-1 signal circuit. See WIRING DIAGRAMS article. If scan tool voltage is 1275 millivolts, go to step 11 . If scan tool voltage is not 1275 millivolts, go to step 9 .
8. Check for an open in HO2S-1 ground circuit. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to step 12 .
9. Check for an open or short to ground in HO2S-1 signal circuit. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to step 12 .
10. Check for a short to voltage in HO2S-1 signal circuit. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to step 12 .
11. Replace HO2S-1. After repairs, go to step 13 .
12. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
13. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Ensure HO2S-1 pigtail is not in contact with exhaust system. Ensure PCM-to-engine grounds are okay. Ensure fuel pressure is correct. If fuel pressure is too low, system will go lean and DTC P0131 may be set. Check for lean fuel injector(s). Check for disconnected or damage vacuum hoses. Check for vacuum leaks at intake manifold, throttle body, EGR and crankcase ventilation systems. Check for exhaust leaks near HO2S-1 that can cause faulty HO2S-1 readings and set DTC P0131.

HO2S-1 contaminated with water could cause a shorted sensor. This occurs more often during wet driving conditions. Silicon contamination of HO2S-1 can cause a low voltage signal. Silicon contamination is indicated by a powdery White deposit on portion of sensor exposed to exhaust stream. Check for fuel contamination from water or excessive alcohol. Before replacing HO2S-1 because of contamination, determine cause of contamination and repair as necessary.

Check for a poor PCM electrical connection. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

HO2S-1 produces a voltage that varies within a range of 100-900 millivolts under normal operating conditions. PCM monitors this voltage and determines if exhaust is lean or rich. If voltage input at PCM is about 100 millivolts, exhaust is lean. If voltage input at PCM is about 900 millivolts, exhaust is rich. PCM constantly monitors HO2S-1 signal during closed loop operation and compensates for a lean or rich condition by adjusting injector pulse width as necessary.

DTC P0132 will set when

1. Intake air temperature is 14-158°F (-10-70°C).
2. Barometric pressure is greater than 11 psi (75 kPa).
3. Vehicle speed is greater than 30 MPH for 2 minutes, and then idled for 2 minutes.
4. Engine is operating in closed loop.
5. Minimum HO2S-1 voltage is greater than 600 millivolts.
6. HO2S-1 voltage remains excessively high for an extended period of time.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer. PCM will enter Fail-Safe Function and EVAP purge control will be stopped.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. If other HO2S-1 DTCs than P0131 and P0132 are set, diagnose DTC(s). If no other HO2S-1 DTCs are set, go to next step.
3. Start engine and allow it to reach normal operating temperature. Increase engine speed to 2000 RPM for one minute. Operate vehicle within conditions required for DTC to set. Using scan tool, monitor HO2S-1 voltage. If voltage decreases to less than 300 millivolts and increases to greater than 600 millivolts, go to next step. If voltage is not as specified, go to step 5 .
4. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If voltage decreases to less than 300 millivolts and increases to greater than 600 millivolts, go to «DIAGNOSTIC AIDS»(ref-189-S21385342892000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article. If voltage is not as specified, go to next step.
5. Disconnect HO2S-1 electrical connector. Using test light connected to battery voltage, probe HO2S-1 connector (harness side) HO2S-1 ground circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 7 .
6. Ensure HO2S-1 electrical connector is disconnected. Using scan tool, monitor HO2S-1 parameter. If voltage is less than 100 millivolts, go to step 9 . If voltage is 100 millivolts or greater, go to step 8 .
7. Check for an open in HO2S-1 ground circuit. Repair as necessary. After repairs, go to step 11 . If circuit is okay, go to step 10 .
8. Check for a short to voltage in HO2S-1 signal circuit. Repair as necessary. After repairs, go to step 11 . If circuit is okay, go to step 10 .
9. Replace HO2S-1. After repairs, go to step 11 .
10. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
11. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Ensure PCM-to-engine grounds are okay. Ensure fuel pressure is correct. If fuel pressure is too high, system will go rich and DTC P0132 may be set. Check for leaking or incorrectly calibrated fuel injector(s). Check for a saturated EVAP canister or faulty EVAP purge control. Check for a leaking fuel pressure regulator or EGR valve. HO2S-1 contaminated with water could cause a shorted sensor. This occurs more often during wet driving conditions.

Check for a poor PCM electrical connection. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Heated Oxygen Sensor-1 (HO2S-1) activity is constantly monitored by PCM. PCM counts number of times a lean-to-rich and rich-to-lean response is indicated. A lean-to-rich transition occurs when HO2S-1 voltage switches from less than 300 millivolts to greater than 600 millivolts. A rich-to-lean transition occurs when HO2S-1 voltage switches from greater than 600 millivolts to less than 300 millivolts. Each response time is measured to obtain an average.

DTC P0133 will set when

1. Intake air temperature is 14-158°F (-10-70°C).
2. Barometric pressure is greater than 11 psi (75 kPa).
3. Vehicle speed is greater than 30 MPH for 2 minutes, and then idled for 2 minutes.
4. Engine is operating in closed loop.
5. Response rate average is greater than one second.
6. Switch cycle average is greater than 5 seconds.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If any other DTCs besides P0133 are set, go to «DIAGNOSTIC AIDS»(ref-189-S19602619442000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article. If no other DTCs are set, go to next step.
3. Ensure HO2S-1 is properly installed. Check for corrosion on HO2S-1 connector terminals. Check for excessive tension on harness connectors at HO2S-1 and PCM. Check for a damaged wiring harness. Check for a contaminated HO2S-1. If any problems are found, go to step 6 . If no problems are found, go to next step.
4. Inspect exhaust system for exhaust leak near engine. If an exhaust leak is found, go to step 6 . If no exhaust leak is found, go to next step.
5. Check HO2S-1 for contamination. Before replacing HO2S-1, determine cause of contamination and repair as necessary. Replace HO2S-1. After repairs, go to step 7 .
6. Repair as necessary. After repairs, go to next step.
7. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

If any other DTCs are set, except for fuel trim (P0171 or P0172), misfire (P0300 to P0304), EGR (P0400) and HO2S-1 (P0131 to P0134), diagnosis those DTCs first. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Heated Oxygen Sensor-1 (HO2S-1) activity is constantly monitored by PCM. PCM counts number of times a lean-to-rich and rich-to-lean response is indicated. A lean-to-rich transition occurs when HO2S-1 voltage switches from less than 300 millivolts to greater than 600 millivolts. A rich-to-lean transition occurs when HO2S-1 voltage switches from greater than 600 millivolts to less than 300 millivolts. Each response time is measured to obtain an average.

DTC P0133 will set when response time for HO2S-1 voltage to change from rich-to-lean, or lean-to-rich is one second or more at idle, during closed loop operation. When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Operate vehicle within freeze frame conditions. If DTC P0133 resets, go to next step. If DTC P0133 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S02967476462000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
3. Ensure HO2S-1 is properly installed. Check for corrosion on HO2S-1 connector terminals. Check for excessive tension on harness connectors at HO2S-1 and PCM. Check for a damaged wiring harness. Repair as necessary. After repairs, go to step 11 . If no problems are found, go to next step.
4. Inspect exhaust system for exhaust leak near engine. Repair as necessary. After repairs, go to step 11 . If no exhaust leak is found, go to next step.
5. Disconnect HO2S-1 electrical connector. Turn ignition on, with engine off. Set DVOM to DC volt scale. Connect DVOM positive lead to battery voltage. Connect negative lead to HO2S-1 connector (harness side) HO2S-1 input circuit. See WIRING DIAGRAMS article. If scan tool voltage is greater than 1155 millivolts, go to next step. If scan tool voltage is 1155 millivolts or less, go to step 7 .
6. Using test light connected to battery voltage, probe HO2S-1 connector (harness side) HO2S-1 ground circuit. See WIRING DIAGRAMS article. If test light illuminates, go to step 9 . If test light does not illuminate, go to step 8 .
7. Check for an open or short in HO2S-1 input circuit between HO2S-1 and PCM. Repair as necessary. After repairs, go to step 11 . If circuit is okay, go to step 10 .
8. Repair open in HO2S-1 ground circuit between HO2S-1 and ground connection. Repair as necessary. After repairs, go to step 11 .
9. Check HO2S-1 for contamination. Before replacing HO2S-1, determine cause of contamination and repair as necessary. Replace HO2S-1. After repairs, go to step 11 .
10. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
11. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

HO2S-1 contaminated with water could cause a shorted sensor. This occurs more often during wet driving conditions. Silicon contamination of HO2S-1 can cause a low voltage signal. Silicon contamination is indicated by a powdery White deposit on portion of sensor exposed to exhaust stream. Check for fuel contamination from water or excessive alcohol. Before replacing HO2S-1 because of contamination, determine cause of contamination and repair as necessary.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

HO2S-1 produces a voltage that varies between 100-900 millivolts under normal operating conditions. PCM monitors this voltage and determines if exhaust is lean or rich. If voltage input at PCM is about 100 millivolts, exhaust is lean. If voltage input at PCM is about 900 millivolts, exhaust is rich. PCM constantly monitors HO2S-1 signal during closed loop operation and compensates for a lean or rich condition by adjusting injector pulse width as necessary.

DTC P0134 will set when

1. Intake air temperature is 14-158°F (-10-70°C).
2. Barometric pressure is greater than 11 psi (75 kPa).
3. Engine is operating in closed loop.
4. Vehicle speed is greater than 30 MPH for 2 minutes, and then idled for 2 minutes.
5. HO2S-1 voltage remains 300 millivolts or less for at least 10 seconds.
6. HO2S-1 voltage remains 600 millivolts or more for at least 10 seconds.
7. HO2S-1 voltage remains outside of active voltage range for an extended period of time.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. If any HO2S-1 DTCs other than P0131, P0132, P0133, P0136, P0171, and P0172 are set, diagnose DTC(s). If no other HO2S-1 DTCs are set, go to next step.
3. Start engine and allow it to reach normal operating temperature. Increase engine speed to 2000 RPM for one minute. Operate vehicle within conditions required for DTC to set. Using scan tool, monitor HO2S-1 voltage. If voltage decreases to less than 300 millivolts and increases to greater than 600 millivolts, go to next step. If voltage is not as specified, go to step 5 .
4. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If voltage decreases to less than 300 millivolts and increases to greater than 600 millivolts, go to «DIAGNOSTIC AIDS»(ref-189-S40962470392000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article. If voltage is not as specified, go to next step.
5. Disconnect HO2S-1 electrical connector. Using scan tool, monitor HO2S-1 parameter. If HO2S-1 voltage is 0-35 millivolts, go to next step. If HO2S-1 voltage is not 0-35 millivolts, go to step 10 .
6. Using test light connected to battery voltage, probe HO2S-1 connector (harness side) HO2S-1 ground circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 10 .
7. Using DVOM, check HO2S-1 signal voltage. Set DVOM to DC volt scale. Connect DVOM positive lead to battery voltage. Connect negative lead to HO2S-1 connector (harness side) HO2S-1 signal circuit. See WIRING DIAGRAMS article. If scan tool voltage is 1275 millivolts, go to step 11 . If scan tool voltage is not 1275 millivolts, go to step 9 .
8. Check for an open in HO2S-1 ground circuit. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to step 12 .
9. Check for an open or short to ground in HO2S-1 signal circuit. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to step 12 .
10. Check for a short to voltage in HO2S-1 signal circuit. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to step 12 .
11. Replace HO2S-1. After repairs, go to step 13 .
12. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
13. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Ensure PCM-to-engine grounds are okay. Check for a faulty HO2S-1. Silicon contamination of HO2S-1 can cause a low voltage signal. Silicon contamination is indicated by a powdery White deposit on portion of sensor exposed to exhaust stream. Check HO2S for soot contamination. Before replacing HO2S-1 because of contamination, determine cause of contamination and repair as necessary.

Check for a poor PCM electrical connection. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Heated Oxygen Sensor-1 (HO2S-1) heater reduces time required to enter closed loop operation, and allows accurate catalyst monitoring by maintaining a sufficiently high temperature. DTC P0135 will set when

1. Resistor voltage is less than 2.5 volts for 5 seconds with heater off.
2. Resistor voltage is greater than .3 volt for 5 seconds with heater on.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If DTC P0135 resets, go to next step. If DTC P0135 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S39903770172000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
3. Turn ignition off. Disconnect HO2S-1 electrical connector. Turn ignition on, with engine off. Using test light connected to ground, probe HO2S-1 connector (harness side) HO2S-1 ignition feed circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 6 .
4. Turn ignition off. Reconnect HO2S-1 electrical connector. Disconnect PCM 16-pin connector. Turn ignition on, with engine off. Using DVOM, measure voltage at PCM 16-pin connector (harness side) HO2S-1 heater control circuit. See WIRING DIAGRAMS article. If voltage is 10 volts, go to next step. If voltage is not 10 volts, go to step 7 .
5. Turn ignition off. Disconnect HO2S-1 electrical connector. Using DVOM, measure resistance between HO2S-1 connector (pigtail side) ignition feed circuit and HO2S-1 heater control circuit. See WIRING DIAGRAMS article. If HO2S-1 heater resistance is 11.7-15.6 ohms at 68°F (20°C), go to step 12 . If HO2S-1 heater resistance is not as specified, go to step 11 .
6. Check IG-COIL fuse (15-amp) located in junction block, behind left side of instrument panel. If fuse is blown, go to step 8 . If fuse is okay, go to step 9 .
7. Check for an open or short to ground in HO2S-1 heater control circuit. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to step 10 .
8. Replace faulty IG-COIL fuse. Check for a short to ground in ignition feed circuit. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to step 11 .
9. Repair open in ignition feed circuit. After repairs, go to step 13 .
10. Check for poor connection at HO2S-1. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to next step.
11. Replace HO2S-1. After repairs, go to step 13 .
12. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
13. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Check for a poor PCM electrical connection. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Heated Oxygen Sensor-1 (HO2S-1) heater reduces time required to enter closed loop operation, and allows accurate catalyst monitoring by maintaining a sufficiently high temperature. DTC P0135 will set when

1. HO2S-1 heater is operating and heater current exceeds 2 amps.
2. HO2S-1 heater is operating and heater current is .2 amp or less.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer. PCM will turn HO2S-1 heater off.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Operate vehicle within freeze frame conditions. If DTC P0135 resets, go to next step. If DTC P0135 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S03588347962000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
3. Disconnect HO2S-1 electrical connector. Turn ignition on, with engine off. Using test light connected to ground, probe HO2S-1 connector (harness side) HO2S-1 ignition feed circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 8 .
4. Turn ignition on, with engine off. Using test light connected to battery voltage, probe HO2S-1 connector (harness side) HO2S-1 heater control circuit. See WIRING DIAGRAMS article. If test light illuminates, go to step 6 . If test light does not illuminate, go to next step.
5. Start and idle engine. If test light illuminates, go to step 9 . If test light does not illuminate, go to step 7 .
6. Check for a short to ground in HO2S-1 heater control circuit. Repair as necessary. After repairs, go to step 12 . If circuit is okay, go to step 11 .
7. Check for an open in HO2S-1 heater control circuit. Repair as necessary. After repairs, go to step 12 . If circuit is okay, go to step 11 .
8. Check for an open in HO2S-1 heater ignition feed circuit. Repair as necessary. After repairs, go to step 12 .
9. Check for poor connection at HO2S-1. Repair as necessary. After repairs, go to step 12 . If connection is okay, go to next step.
10. Replace HO2S-1. After repairs, go to step 12 .
11. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
12. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Check for a poor PCM electrical connection. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

PCM has the ability to monitor efficiency of Three-Way Catalyst (TWC) by using HO2S-1 and HO2S-2. HO2S-1 produces an output signal indicating oxygen content in exhaust gases entering TWC. HO2S-2 produces an output signal indicating oxygen storage capacity of TWC. A comparison reading from HO2S-1 and HO2S-2 determines TWC's ability to convert exhaust gases efficiently. If TWC is operating efficiently, HO2S-1 will be far more active than HO2S-2.

DTC P0136 will set when

1. Engine speed is greater than 1500 RPM.
2. Fuel level is greater than 25 percent.
3. Engine coolant temperature is 176°F (80°C) or more.
4. Intake air temperature is 14-158°F (-10-70°C).
5. Barometric pressure is greater than 11 psi (75 kPa).
6. Vehicle speed is 20-50 MPH.
7. Engine is operating in closed loop.
8. Maximum HO2S-2 voltage is less than 600 millivolts for at least 8 minutes.
9. Minimum HO2S-2 voltage is 300 millivolts or more for 5 seconds after maximum voltage check during fuel shut-off mode for 5 seconds.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Allow engine to cool for 2 minutes. Connect scan tool to DLC. Turn ignition on, with engine off. Using scan tool, monitor HO2S-2 parameter. Start engine. Run engine at 2000 RPM for about 5 minutes. If HO2S-2 voltage is 1275 millivolts and decreases as engine warms, go to next step. If HO2S-2 voltage is not as specified, go to step 4 .
3. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If DTC P0136 resets, go to next step. If DTC P0136 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S28705469612000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
4. Turn ignition on, with engine off. Disconnect HO2S-2 electrical connector. Using DVOM, measure voltage between ground and HO2S-2 connector (harness side) HO2S-2 signal circuit. See WIRING DIAGRAMS article. If voltage is 4-5 volts, go to next step. If voltage is not 4-5 volts, go to step 8 .
5. Using scan tool, monitor HO2S-2 parameter. Connect a fused jumper wire between HO2S-2 signal circuit (PCM side) and ground. See WIRING DIAGRAMS article. If scan tool indicates HO2S-2 voltage less than 100 millivolts, go to next step. If voltage is not as specified, go to step 11 .
6. Turn ignition on, with engine off. Using test light connected to battery voltage, probe HO2S-2 ground circuit (PCM side). See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 9 .
7. Replace HO2S-2. After repairs, go to step 12 .
8. Check for poor connections or an open in HO2S-2 signal circuit between HO2S-2 and PCM. Repair as necessary. After repairs, go to step 12 . If connections and circuit are okay, go to step 10 .
9. Check for poor connections or an open in HO2S-2 ground circuit. Repair as necessary. After repairs, go to step 12 . If connections and circuit are okay, go to step 11 .
10. Check for a short in HO2S-2 signal circuit. Repair as necessary. After repairs, go to step 12 . If circuit is okay, go to next step.
11. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
12. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Inspect exhaust system for leaks between TWC flanges. Ensure HO2S-2 pigtail is not in contact with exhaust system. Check HO2S-2 for damage. HO2S-2 is located under vehicle chassis and is easily damaged by road hazards. HO2S-2 contaminated with water could cause a shorted sensor. This occurs more often during wet driving conditions. Before replacing HO2S-1 because of contamination, determine cause of contamination and repair as necessary.

Check for a poor PCM electrical connection. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

PCM has the ability to monitor efficiency of Three-Way Catalyst (TWC) by using HO2S-1 and HO2S-2. HO2S-1 produces an output signal indicating oxygen content in exhaust gases entering TWC. HO2S-2 produces an output signal indicating oxygen storage capacity of TWC. A comparison reading from HO2S-1 and HO2S-2 determines TWC's ability to convert exhaust gases efficiently. If TWC is operating efficiently, HO2S-1 will be far more active than HO2S-2.

DTC P0136 will set when

1. Average voltage of HO2S-2 is .4 volt or more, engine speed is greater than 1600 RPM, and engine coolant temperature is 158°F (70°C) or more.
2. Average voltage of HO2S-2 is .5 volt or less, engine speed is greater than 1600 RPM, and engine coolant temperature is 158°F (70°C) or more.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer. PCM will turn HO2S-2 heater off.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Operate vehicle within freeze frame conditions. If DTC P0136 resets, go to next step. If DTC P0136 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S37694960792000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
3. Disconnect HO2S-2 electrical connector. Turn ignition on, with engine off. Set DVOM to DC volt scale. Connect DVOM positive lead to battery voltage. Connect negative lead to HO2S-2 connector (harness side) HO2S-2 input circuit. See WIRING DIAGRAMS article. Using scan tool, monitor HO2S-2 parameter. If scan tool voltage is about 1155 millivolts, go to next step. If scan tool voltage is not about 1155 millivolts, go to step 5 .
4. Using test light connected to battery voltage, probe HO2S-2 connector (harness side) HO2S-2 ground circuit. See WIRING DIAGRAMS article. If test light illuminates, go to step 7 . If test light does not illuminate, go to step 6 .
5. Check for an open or short in HO2S-2 input circuit between HO2S-2 and PCM. Repair as necessary. After repairs, go to step 9 . If circuit is okay, go to step 8 .
6. Repair open in HO2S-2 ground circuit between HO2S-2 and ground connection. Repair as necessary. After repairs, go to step 9 . If circuit is okay, go to step 8 .
7. Replace HO2S-2. After repairs, go to step 9 .
8. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
9. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Check for a poor PCM electrical connection. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Heated Oxygen Sensor-2 (HO2S-2) heater reduces time required to enter closed loop operation, and allows accurate catalyst monitoring by maintaining a sufficiently high temperature. DTC P0141 will set when

1. Resistor voltage is less than 2.5 volts for 5 seconds with heater off.
2. Resistor voltage is greater than .3 volt for 5 seconds with heater on.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If DTC P0141 resets, go to next step. If DTC P0141 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S40118656782000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
3. Turn ignition off. Disconnect HO2S-2 electrical connector. Turn ignition on, with engine off. Using test light connected to ground, probe HO2S-2 connector (harness side) HO2S-2 ignition feed circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 6 .
4. Turn ignition off. Reconnect HO2S-2 electrical connector. Disconnect PCM 26-pin connector. Turn ignition on, with engine off. Using DVOM, measure voltage at PCM 26-pin connector (harness side) HO2S-2 heater control circuit. See WIRING DIAGRAMS article. If voltage is 10 volts, go to next step. If voltage is not 10 volts, go to step 7 .
5. Turn ignition off. Disconnect HO2S-2 electrical connector. Using DVOM, measure resistance between HO2S-2 connector (pigtail side) ignition feed circuit and HO2S-2 heater control circuit. See WIRING DIAGRAMS article. If HO2S-2 heater resistance is 11.7-15.6 ohms at 68°F (20°C), go to step 12 . If HO2S-2 heater resistance is not as specified, go to step 11 .
6. Check IG-COIL fuse (15-amp) located in junction block, behind left side of instrument panel. If fuse is blown, go to step 8 . If fuse is okay, go to step 9 .
7. Check for an open or short to ground in HO2S-2 heater control circuit. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to step 10 .
8. Replace faulty IG-COIL fuse. Check for a short to ground in ignition feed circuit. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to step 11 .
9. Repair open in ignition feed circuit. After repairs, go to step 13 .
10. Check for poor connection at HO2S-2. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to next step.
11. Replace HO2S-2. After repairs, go to step 13 .
12. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
13. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Check for a poor PCM electrical connection. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Heated Oxygen Sensor-2 (HO2S-2) heater reduces time required to enter closed loop operation, and allows accurate catalyst monitoring by maintaining a sufficiently high temperature. DTC P0141 will set when

1. HO2S-2 heater is operating and heater current exceeds 2 amps.
2. HO2S-2 heater is operating and heater current is .2 amp or less.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer. PCM will turn HO2S-2 heater off.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Operate vehicle within freeze frame conditions. If DTC P0141 resets, go to next step. If DTC P0141 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S03960356112000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
3. Disconnect HO2S-2 electrical connector. Turn ignition on, with engine off. Using test light connected to ground, probe HO2S-2 connector (harness side) HO2S-2 ignition feed circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 8 .
4. Turn ignition on, with engine off. Using test light connected to battery voltage, probe HO2S-2 connector (harness side) HO2S-2 heater control circuit. See WIRING DIAGRAMS article. If test light illuminates, go to step 6 . If test light does not illuminate, go to next step.
5. Start and idle engine. If test light illuminates, go to step 9 . If test light does not illuminate, go to step 7 .
6. Check for a short to ground in HO2S-2 heater control circuit. Repair as necessary. After repairs, go to step 12 . If circuit is okay, go to step 11 .
7. Check for an open in HO2S-2 heater control circuit. Repair as necessary. After repairs, go to step 12 . If circuit is okay, go to step 11 .
8. Check for an open in HO2S-2 heater ignition feed circuit. Repair as necessary. After repairs, go to step 12 .
9. Check for poor connection at HO2S-2. Repair as necessary. After repairs, go to step 12 . If connection is okay, go to next step.
10. Replace HO2S-2. After repairs, go to step 12 .
11. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
12. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Check for a poor PCM electrical connection. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

To provide best possible combination of driveability, fuel economy, and emission control, a closed loop air/fuel metering system is used. During closed loop, PCM monitors heated oxygen sensor signal voltage and adjusts fuel delivery accordingly. A change made to fuel delivery is indicated by long and short term fuel trim values and can be monitored using a scan tool. Ideal fuel trim values are around zero percent.

If a rich condition exists, fuel trim values will be less than zero percent indicating PCM is reducing amount of fuel delivered. If a lean condition exists, fuel trim values will be more than zero percent indicating PCM is increasing amount of fuel delivered. A fuel trim DTC can set if exhaust emissions exceed preset levels because of a lean or rich condition. DTC P0171 will set when

1. Fuel level is greater than 25 percent.
2. Intake air temperature is 14-158°F (-10-70°C).
3. Barometric pressure is greater than 11 psi (75 kPa).
4. Long and short term fuel trim is 30 percent or more for 5 seconds.
5. Short term fuel trim is 20 percent or more for 45 seconds.
6. Engine is running at a steady speed and operating in closed loop.

When DTC sets, MIL will illuminate. PCM will record operating conditions at time of failure and store information in freeze frame buffer. PCM will enter Fail-Safe Function. EGR and EVAP purge control will be stopped.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Start engine and allow it to reach normal operating temperature. Operate vehicle while scan tool indicates CLOSED LOOP. Using scan tool, monitor short term Fuel Trim (FT) parameter. If fuel trim value is 0-20 percent, go to next step. If fuel trim value is not 0-20 percent, go to step 4 .
3. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. Using scan tool, monitor long and short term FT parameters, and add together. If combined fuel trim values are 0-30 percent, go to «DIAGNOSTIC AIDS»(ref-189-S28501254142000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article. If combined fuel trim values are not 0-30 percent, go to next step.
4. Check vacuum hoses for splits, kinks and improper connections. Check PCV valve for proper operation. Check exhaust system for leaks. Check EGR system for proper operation. Repair as necessary. After repairs, go to step 11 . If no problems are found, go to next step.
5. Start engine and warm to normal operating temperature. Using scan tool, monitor operation of MAP, ECT and TP sensors with engine idling. Check sensors for proper calibration and operation. See «SCAN TOOL DATA»(ref-189-S01138772912000030800000) under SELF-DIAGNOSTIC SYSTEM. Check vehicle for cause of any erratic sensor readings and repair as necessary. After repairs, go to step 11 . If no problems are found, go to next step.
6. Turn ignition off. Install fuel pressure gauge. See BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article. Start engine. Observe fuel pressure at idle with engine at normal operating temperature. If fuel pressure is 13-20 psi (0.9-1.4 kg/cm 2 ), go to next step. If fuel pressure is not as specified, go to BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
7. Check fuel for excessive water, alcohol, or other contaminants. If fuel is contaminated, go to next step. If fuel is okay, go to step 9 .
8. Replace contaminated fuel as necessary. After repairs, go to step 11 .
9. Check for clogging or other restrictions in fuel injector. Using a timing light, ensure injector fuel spray is in a conical pattern. Ensure that injector resistance is 0.5-1.5 ohms at 68°F (20°C). If no problems are found, go to «DIAGNOSTIC AIDS»(ref-189-S28501254142000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article. If problem is found, go to next step.
10. Repair or replace fuel injector. After repairs, go to next step.
11. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Ensure fuel pressure is within specifications. Fuel pressure that is too low will cause a lean condition. Check for vacuum and exhaust leaks. Check MAP sensor for correct values. A MAP sensor that reads high vacuum will cause a lean condition. When MAP sensor is disconnected, PCM will substitute a default value. If lean condition goes away, replace MAP sensor and recheck system. Check for fuel contamination. Small amounts of water in fuel tank can cause DTC P0171 to set. Check for a HO2S silicone and other contaminants.

Check for a poor PCM electrical connection. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

To provide best possible combination of driveability, fuel economy, and emission control, a closed loop air/fuel metering system is used. During closed loop, PCM monitors heated oxygen sensor signal voltage and adjusts fuel delivery accordingly. A change made to fuel delivery is indicated by long and short term fuel trim values and can be monitored using a scan tool. Ideal fuel trim values are around zero percent.

If a rich condition exists, fuel trim values will be less than zero percent indicating PCM is reducing amount of fuel delivered. If a lean condition exists, fuel trim values will be more than zero percent indicating PCM is increasing amount of fuel delivered. A fuel trim DTC can set if exhaust emissions exceed preset levels because of a lean or rich condition. DTC P0171 will set when air fuel ratio is stable after engine is in closed loop operation and fuel trim indicates considerably rich.

When DTC sets, MIL will illuminate. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Start engine and allow it to reach normal operating temperature. Operate vehicle while scan tool indicates CLOSED LOOP. Using scan tool, monitor short term Fuel Trim (FT) parameter. If fuel trim value is 0-20 percent, go to «DIAGNOSTIC AIDS»(ref-189-S10078018602000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article. If fuel trim value is not 0-20 percent, go to next step.
3. Check vacuum hoses for splits, kinks and improper connections. Check PCV valve for proper operation. Check exhaust system for leaks. Check EGR system for proper operation. Repair as necessary. After repairs, go to step 10 . If no problems are found, go to next step.
4. Start engine and warm to normal operating temperature. Using scan tool, monitor operation of MAP, ECT and TP sensors with engine idling. Check sensors for proper calibration and operation. See «SCAN TOOL DATA»(ref-189-S01138772912000030800000) under SELF-DIAGNOSTIC SYSTEM. Check vehicle for cause of any erratic sensor readings and repair as necessary. After repairs, go to step 10 . If no problems are found, go to next step.
5. Turn ignition off. Install fuel pressure gauge. See BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article. Start engine. Observe fuel pressure at idle with engine at normal operating temperature. If fuel pressure is 44-50 psi (3.0-3.5 kg/cm 2 ), go to next step. If fuel pressure is not as specified, go to BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
6. Check fuel for excessive water, alcohol, or other contaminants. If fuel is contaminated, go to next step. If fuel is okay, go to step 8 .
7. Replace contaminated fuel as necessary. After repairs, go to step 10 .
8. Perform FUEL INJECTOR COIL TEST - ENGINE COOLANT TEMPERATURE BETWEEN 50-95°F (1.8L) under CIRCUIT TESTS in appropriate SYSTEM & COMPONENT TESTING article. Repair or replace as necessary. After repairs, go to step 10 . If no problems are found, go to next step.
9. If lean condition is still present, diagnosis by symptom. See appropriate TROUBLE SHOOTING - NO CODES article. If lean condition is not present, go to next step.
10. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Ensure fuel pressure is within specifications. Fuel pressure that is too low will cause a lean condition. Check for vacuum and exhaust leaks. Check MAP sensor for correct values. A MAP sensor that reads high vacuum will cause a lean condition. When MAP sensor is disconnected, PCM will substitute a default value. If lean condition goes away, replace MAP sensor and recheck system. Check for fuel contamination. Small amounts of water in fuel tank can cause DTC P0171 to set. Check for a HO2S silicone and other contaminants.

Check for a poor PCM electrical connection. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

To provide best possible combination of driveability, fuel economy, and emission control, a closed loop air/fuel metering system is used. During closed loop, PCM monitors heated oxygen sensor signal voltage and adjusts fuel delivery accordingly. A change made to fuel delivery is indicated by long and short term fuel trim values and can be monitored using a scan tool. Ideal fuel trim values are around zero percent.

If a rich condition exists, fuel trim values will be less than zero percent indicating PCM is reducing amount of fuel delivered. If a lean condition exists, fuel trim values will be more than zero percent indicating PCM is increasing amount of fuel delivered. A fuel trim DTC can set if exhaust emissions exceed preset levels because of a lean or rich condition. DTC P0172 will set when

1. Fuel level is greater than 25 percent.
2. Intake air temperature is 14-158°F (-10-70°C).
3. Barometric pressure is greater than 11 psi (75 kPa).
4. Engine is running at a steady speed and operating in closed loop.
5. Long and short term fuel trim is -30 percent or more for 5 seconds.
6. Short term fuel trim is -20 percent or more for 45 seconds.

When DTC sets, MIL will illuminate. PCM will record operating conditions at time of failure and store information in freeze frame buffer. PCM will enter Fail-Safe Function. EGR and EVAP purge control will be stopped.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Start engine and allow it to reach normal operating temperature. Operate vehicle while scan tool indicates CLOSED LOOP. Using scan tool, monitor short term Fuel Trim (FT) parameter. If fuel trim value is greater than -20 percent, go to next step. If fuel trim value is less than -20 percent, go to step 4 .
3. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. Using scan tool, monitor long and short term FT parameters, and add together. If combined fuel trim values are greater than -30 percent, go to «DIAGNOSTIC AIDS»(ref-189-S05321311782000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article. If combined fuel trim values are -30 percent or less, go to next step.
4. Check air filter and air filter assembly for restrictions. Repair as necessary. After repairs, go to step 10 . If no problems are found, go to next step.
5. Turn ignition off. Install fuel pressure gauge. See BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article. Start engine. Observe fuel pressure at idle with engine at normal operating temperature. If fuel pressure is 13-20 psi (0.9-1.4 kg/cm 2 ), go to next step. If fuel pressure is not as specified, go to BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
6. Check EVAP control system for possible over purging of vapors. Repair as necessary. After repairs, go to step 10 . If EVAP control system is okay, go to next step.
7. Remove HO2S-1. Check HO2S-1 for contamination or damage. Before replacing HO2S-1, determine cause of contamination or damage, and repair as necessary. Replace HO2S-1. After repairs, go to step 10 . If HO2S-1 is okay, go to next step.
8. Check for leaking fuel injector needle valve. Using a timing light, ensure injector fuel spray is in a conical pattern. Ensure that injector resistance is 0.5-1.5 ohms at 68°F (20°C). If no problems are found, go to «DIAGNOSTIC AIDS»(ref-189-S05321311782000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article. If problem is found, go to next step.
9. Repair or replace fuel injector. After repairs, go to next step.
10. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Check for a restriction in inlet air passage. A duct or inlet hose that collapses when hot or is blocked by debris can cause DTC P0172 to set. Ensure fuel pressure is within specifications. Fuel pressure that is too high will cause a rich condition. Check MAP sensor for correct values. A MAP sensor that reads low vacuum will cause a rich condition. When MAP sensor is disconnected, PCM will substitute a default value. If rich condition goes away, replace MAP sensor and recheck system. Check for fuel contamination. Small amounts of water in fuel tank can cause DTC P0172 to set. Check for a HO2S silicone and other contaminants.

Check for a poor PCM electrical connection. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

To provide best possible combination of driveability, fuel economy, and emission control, a closed loop air/fuel metering system is used. During closed loop, PCM monitors heated oxygen sensor signal voltage and adjusts fuel delivery accordingly. A change made to fuel delivery is indicated by long and short term fuel trim values and can be monitored using a scan tool. Ideal fuel trim values are around zero percent.

If a rich condition exists, fuel trim values will be less than zero percent indicating PCM is reducing amount of fuel delivered. If a lean condition exists, fuel trim values will be more than zero percent indicating PCM is increasing amount of fuel delivered. A fuel trim DTC can set if exhaust emissions exceed preset levels because of a lean or rich condition. DTC P0172 will set when air fuel ratio is stable after engine is in closed loop operation and fuel trim indicates considerably lean.

When DTC sets, MIL will illuminate. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Start engine and allow it to reach normal operating temperature. Operate vehicle while scan tool indicates CLOSED LOOP. Using scan tool, monitor short term Fuel Trim (FT) parameter. If fuel trim value is greater than -20 percent, go to «DIAGNOSTIC AIDS»(ref-189-S08209114632000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article. If fuel trim value is -20 percent or less, go to next step.
3. Check air filter and air filter assembly for restrictions. Repair as necessary. After repairs, go to step 9 . If no problems are found, go to next step.
4. Start engine and warm to normal operating temperature. Using scan tool, monitor operation of HO2S-1, MAP and ECT sensors with engine idling. Check sensors for proper calibration and operation. See «SCAN TOOL DATA»(ref-189-S01138772912000030800000) under SELF-DIAGNOSTIC SYSTEM. Check vehicle for cause of any erratic sensor readings and repair as necessary. After repairs, go to step 9 . If no problems are found, go to next step.
5. Turn ignition off. Install fuel pressure gauge. See BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article. Start engine. Observe fuel pressure at idle with engine at normal operating temperature. If fuel pressure is 44-50 psi (3.0-3.5 kg/cm 2 ), go to next step. If fuel pressure is not as specified, go to BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
6. Check EVAP control system for possible over purging of vapors. Repair as necessary. After repairs, go to step 9 . If EVAP control system is okay, go to next step.
7. Remove HO2S-1. Check HO2S-1 for contamination or damage. Before replacing HO2S-1, determine cause of contamination or damage, and repair as necessary. Replace HO2S-1. After repairs, go to step 9 . If HO2S-1 is okay, go to next step.
8. If rich condition is still present, diagnosis by symptom. See appropriate TROUBLE SHOOTING - NO CODES article. If rich condition is not present, go to next step.
9. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Check for a restriction in inlet air passage. A duct or inlet hose that collapses when hot or is blocked by debris can cause DTC P0172 to set. Ensure fuel pressure is within specifications. Fuel pressure that is too high will cause a rich condition. Check MAP sensor for correct values. A MAP sensor that reads low vacuum will cause a rich condition. When MAP sensor is disconnected, PCM will substitute a default value. If rich condition goes away, replace MAP sensor and recheck system. Check for fuel contamination. Small amounts of water in fuel tank can cause DTC P0172 to set. Check for a HO2S silicone and other contaminants.

Check for a poor PCM electrical connection. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

PCM uses Crankshaft Position (CKP) sensor and Camshaft Position (CMP) sensor to monitor changes in crankshaft rotation for each cylinder to detect a misfire. If a difference in crankshaft rotation for a specific cylinder(s) is present, MIL will illuminate. If difference in crankshaft rotation is significant, MIL will flash, indicating a catalytic converter damaging condition. DTC P0300 will set when

1. Engine coolant temperature is greater than 158°F (70°C).
2. Intake air temperature is 14-122°F (-10-50°C).
3. Barometric pressure is greater than 11 psi (75 kPa).
4. Engine speed is less than 6500 RPM and change is less than 200 per 50 milliseconds.
5. MAP change is less than 1.9 psi (13 kPa) per 60 firing events.
6. TP change is less than 1.9 psi (13 kPa) per 16 firing events.
7. Fuel tank level is greater than 25 percent.
8. Conditions are present for 5 seconds after engine is started to one second from fuel shutoff.

When DTC sets, PCM will flash MIL the first time catalytic converter damage occurs. MIL will illuminate second time emission thresholds are exceeded (second time diagnostic fails). PCM will record operating conditions at time of failure and store information in freeze frame buffer. PCM will enter Fail-Safe Function and EGR control will be stopped.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Start engine. If a misfire is present at idle, go to step 4 . If no misfire is present, go to next step.
3. Connect scan tool to DLC. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If DTC P0300 resets, go to next step. If DTC P0300 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S20695606972000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
4. Install a Spark Tester (J-26792) to each spark plug wire individually. Crank engine and observe spark tester. If a crisp, Blue spark is present on each wire, go to step 9 . If spark is weak or no spark is present, go to next step.
5. Remove and inspect spark plug wires for carbon tracking and insulation damage. Repair as necessary. After repairs, go to step 16 . If wires are okay, go to next step.
6. Using DVOM, measure resistance of each spark plug wire. If resistance is 3000-6700 ohms per foot, go to next step. If resistance is greater than 6700 ohms per foot, replace spark plug wire. After repairs, go to step 16 .
7. Inspect distributor cap and rotor for moisture, cracks, carbon tracking, or poor terminal connection. Repair as necessary. After repairs, go to step 16 . If cap and rotor are okay, go to next step.
8. Check signal rotor located in distributor for damage. Ensure air gap is .008-.016" (.2-.4 mm). Adjust or repair as necessary. After repairs, go to step 16 . If signal rotor is okay, go to step 14 .
9. Remove and inspect spark plugs. Check for improper gap, cracked ceramic insulators or electrodes, carbon tracking, oil or fuel fouling, evidence of coolant, loose center electrode or terminal end, or missing platinum pads. Replace spark plugs as necessary. After repairs, go to step 16 . If spark plugs are okay, go to next step.
10. Turn ignition off. Install fuel pressure gauge. See BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article. Start engine. Observe fuel pressure at idle with engine at normal operating temperature. If fuel pressure is 13-20 psi (0.9-1.4 kg/cm 2 ), go to next step. If fuel pressure is not as specified, go to BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
11. Check fuel for contamination. If fuel is contaminated, go to next step. If fuel is okay, go to step 13 .
12. Replace contaminated fuel as necessary. After repairs, go to step 16 .
13. Check for an engine mechanical problem. Check for faulty or incorrect camshaft, leaky or sticky valves or piston rings, excessive valve deposits, loose or worn rocker arms, weak valve springs, incorrect valve timing, vacuum leaks, leaking head gasket, and a loose or broken motor mount. Repair as necessary. After repairs, go to step 16 . If no mechanical problems are found, go to «DIAGNOSTIC AIDS»(ref-189-S20695606972000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
14. Check ignition coil for cracks. Measure resistance of ignition coil. Primary coil resistance should be 1.08-1.32 ohms at 68°F (20°C). Secondary resistance should be 22,100-29,900 ohms at 68°F (20°C). If a faulty ignition coil is found, go to next step. If ignition coils are okay, go to «DIAGNOSTIC AIDS»(ref-189-S20695606972000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
15. Replace faulty ignition coil. After repairs, go to next step.
16. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

If any DTCs other than misfire DTCs P0300-P0303 are present, diagnose those DTCs first. Check for engine overheating, vacuum leaks or improper EGR system operation. Ensure PCV valve is operating properly. Check ignition system for a malfunction, including spark plugs, spark plug wires, ignition coil, and distributor. Ensure fuel pressure is correct and fuel injectors are operating properly. Check engine mechanical operation, including cylinder compression and valve adjustment function.

Check for conditions or faulty components which could cause an engine misfire. See appropriate TROUBLE SHOOTING - NO CODES article. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

PCM uses Crankshaft Position (CKP) sensor and Camshaft Position (CMP) sensor to monitor changes in crankshaft rotation for each cylinder to detect a misfire. If a difference in crankshaft rotation for a specific cylinder(s) is present, MIL will illuminate. If difference in crankshaft rotation is significant, MIL will flash, indicating a catalytic converter damaging condition. DTC P0300 will set when

1. Engine coolant temperature is 14-230°F (-10-110°C).
2. Intake air temperature is 14-158°F (-10-70°C).
3. Barometric pressure is greater than 11 psi (75 kPa).
4. Engine speed is less than 6500 RPM and change is less than 200 per 50 milliseconds.
5. MAP change is less than .19 psi (1.3 kPa) per 60 firing events.
6. TP change is less than 1.9 degrees per 16 firing events.
7. Conditions are present for 5 seconds after engine is started to one second from fuel shutoff.

When DTC sets, PCM will flash MIL the first time catalytic converter damage occurs. MIL will illuminate second time emission thresholds are exceeded (second time diagnostic fails). PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Start engine. If a misfire is present at idle, go to step 4 . If no misfire is present, go to next step.
3. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If DTC P0300 resets, go to next step. If DTC P0300 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S20360500052000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
4. Check for improperly operating or leaking PCV valve. Ensure PCV valve is correct for vehicle. Check for vacuum leak at intake manifold or gasket. Check for cracked, split or worn vacuum hose. Repair as necessary. After repairs, go to step 17 . If no problem is found, go to next step.
5. Install a Spark Tester (J-26792) to each spark plug wire individually. Crank engine and observe spark tester. If a crisp, Blue spark is present on each wire, go to step 10 . If spark is weak or no spark is present, go to next step.
6. Remove and inspect spark plug wires for carbon tracking and insulation damage. Repair as necessary. After repairs, go to step 17 . If wires are okay, go to next step.
7. Using DVOM, measure resistance of each spark plug wire. If resistance is 1200-3000 ohms per foot, go to next step. If resistance is greater than 3000 ohms per foot, replace spark plug wire. After repairs, go to step 17 .
8. Inspect ignition coils for moisture, cracks, corrosion, carbon tracking, or poor terminal connection. Repair as necessary. After repairs, go to step 17 . If ignition coils are okay, go to next step.
9. Replace ignition coil on cylinder that spark was not present. After repairs, go to step 17 .
10. Remove and inspect spark plugs. Check for improper gap, cracked ceramic insulators or electrodes, carbon tracking, oil or fuel fouling, evidence of coolant, loose center electrode or terminal end, or missing platinum pads. Replace spark plugs as necessary. After repairs, go to step 13 . If spark plugs are okay, go to next step.
11. Turn ignition off. Disconnect fuel injector electrical connectors. Install Injector Test Light (J-34730-2B) on each fuel injector harness connector one at a time. Crank engine and observe test light. If test light flashes for each injector, go to next step. If test light does not flash for each injector, go to FUEL INJECTOR CIRCUIT (1.3L) under CIRCUIT TESTS in appropriate SYSTEM & COMPONENT TESTING article.
12. Check fuel injectors for proper operation. See FUEL INJECTOR COIL TEST - ENGINE COOLANT TEMPERATURE BETWEEN 50-95°F (1.3L) under CIRCUIT TESTS in appropriate SYSTEM & COMPONENT TESTING article. Replace fuel injector(s) as necessary. After repairs, go to step 17 . If fuel injectors are okay, go to step 14 .
13. If spark plug was replaced because of fuel, oil or coolant fouling, go to next step. If spark plug was not replaced because of fuel, oil or coolant fouling, go to step 17 .
14. Check for an engine mechanical problem. Check for faulty or incorrect camshaft, leaky or sticky valves or piston rings, excessive valve deposits, loose or worn rocker arms, weak valve springs, incorrect valve timing, vacuum leaks, leaking head gasket, and a loose or broken motor mount. Repair as necessary. After repairs, go to step 17 . If no mechanical problems are found, go to next step.
15. Remove CKP sensor. Check CKP sensor for damage. Check for foreign material on sensor surface. Check for water or corrosion at electrical terminals. Repair as necessary. After repairs, go to step 17 . If CKP sensor is okay, go to next step.
16. Check CKP sensor signal rotor on crankshaft timing belt pulley for damaged teeth, foreign material or incorrect installation. Repair as necessary. After repairs, go to next step. If CKP sensor signal rotor is okay, go to «DIAGNOSTIC AIDS»(ref-189-S20360500052000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
17. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

If any DTCs other than misfire DTCs P0300-P0304 are present, diagnose those DTCs first. Check for engine overheating, vacuum leaks or improper EGR system operation. Ensure PCV valve is operating properly. Check ignition system for a malfunction, including spark plugs, spark plug wires, and ignition coil. Ensure fuel pressure is correct and fuel injectors are operating properly. Water in fuel may cause an intermittent misfire. Check engine mechanical operation, including cylinder compression and valve adjustment function.

Check for conditions or faulty components which could cause an engine misfire. See appropriate TROUBLE SHOOTING - NO CODES article. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

PCM uses Crankshaft Position (CKP) sensor and Camshaft Position (CMP) sensor to monitor changes in crankshaft rotation for each cylinder to detect a misfire. When misfire rate equals or exceeds a count indicating engine condition has deteriorated, MIL will illuminate. If misfire rate is significant, MIL will flash, indicating a catalytic converter damaging condition. DTC P0300 will set when engine speed is 200-4000 RPM, battery voltage is 9-17 volts, engine coolant temperature is 20-254°F (-7-123°C), and misfire is indicated in more than one cylinder simultaneously.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault causing deterioration in emissions. MIL will flash if misfire is severe enough to cause catalyst damage.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Start engine. Using scan tool, monitor TOTAL MISFIRE CURRENT COUNT parameter. If scan tool indicates any misfire counts, go to step 4 . If scan tool does not indicate any misfire counts, go to next step.
3. Turn ignition on, with engine off. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Operate vehicle within freeze frame conditions. If DTC P0300 resets or scan tool indicates any misfire counts, go to next step. If DTC P0300 does not reset and scan tool does not indicate any misfire counts, go to «DIAGNOSTIC AIDS»(ref-189-S30129435772000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
4. Install a Spark Tester (J-26792) to each spark plug wire individually. Crank engine and observe spark tester. If a crisp, Blue spark is present on each wire, go to step 8 . If spark is weak or no spark is present, go to next step.
5. Remove and inspect spark plug wires for carbon tracking and insulation damage. Repair as necessary. Using DVOM, measure resistance of each spark plug wire. If resistance is 25,000 ohms, go to step 15 . If resistance is not 25,000 ohms, go to next step.
6. Inspect ignition coils for moisture, cracks, corrosion, carbon tracking, or poor terminal connection. Repair as necessary. After repairs, go to step 17 . If ignition coils are okay, go to next step.
7. Remove CKP sensor. Check CKP sensor signal rotor through sensor hole for damaged teeth, dents or nicks. Repair as necessary. After repairs, go to step 17 . If CKP sensor signal rotor is okay, go to step 14 .
8. Remove and inspect spark plugs. Check for improper gap, cracked ceramic insulators or electrodes, carbon tracking, oil or fuel fouling, evidence of coolant, loose center electrode or terminal end, or missing platinum pads. Replace spark plugs as necessary. After repairs, go to step 17 . If spark plugs are okay, go to next step.
9. Turn ignition off. Disconnect fuel injector electrical connectors. Install Injector Test Light (J-34730-2B) on each fuel injector harness connector one at a time. Crank engine and observe test light. If test light flashes for each injector, go to next step. If test light does not flash for each injector, go to FUEL INJECTOR CIRCUIT (1.8L) under CIRCUIT TESTS in appropriate SYSTEM & COMPONENT TESTING article.
10. Check fuel injectors for proper operation. See FUEL INJECTOR COIL TEST - ENGINE COOLANT TEMPERATURE BETWEEN 50-95°F (1.8L) and FUEL INJECTOR BALANCE TEST (1.8L) under CIRCUIT TESTS in appropriate SYSTEM & COMPONENT TESTING article. Replace fuel injector(s) as necessary. After repairs, go to step 17 . If fuel injectors are okay, go to next step.
11. Turn ignition off. Install fuel pressure gauge. See BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article. Start engine. Observe fuel pressure at idle with engine at normal operating temperature. If fuel pressure is 44-50 psi (3.0-3.5 kg/cm 2 ), go to next step. If fuel pressure is not as specified, go to BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
12. Check for alcohol or other contaminates in fuel. Check fuel type and quality. Replace contaminated fuel as necessary. After repairs, go to step 17 . If fuel is okay, go to next step.
13. Check for vacuum leaks at PCV valve, intake manifold gasket, vacuum lines, hoses and fittings. Repair as necessary. After repairs, go to step 17 . If no problem is found, go to step 16 .
14. Replace faulty ignition coil. After repairs, go to step 17 .
15. Replace faulty spark plug wires. After repairs, go to step 17 .
16. Check for an engine mechanical problem. Check for faulty or incorrect camshaft, leaky or sticky valves or piston rings, excessive valve deposits, loose or worn rocker arms, weak valve springs, incorrect valve timing, vacuum leaks, leaking head gasket, and a loose or broken motor mount. Repair as necessary. After repairs, go to next step. If no mechanical problems are found, go to «DIAGNOSTIC AIDS»(ref-189-S30129435772000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
17. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

If any DTCs other than misfire DTCs P0300-P0304 are present, diagnose those DTCs first. Check for engine overheating. Ensure PCV valve is operating properly. Check ignition system for a malfunction, including spark plugs, spark plug wires, and ignition coil. An intermittent can result from a defective crankshaft reluctor wheel. Remove CKP sensor and inspect reluctor wheel for porosity, nicks, dents or other damage.

Check for conditions or faulty components which could cause an engine misfire. See appropriate TROUBLE SHOOTING - NO CODES article. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Start engine. If a misfire is present at idle, go to step 4 . If no misfire is present, go to next step.
3. Connect scan tool to DLC. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If related DTC P0301, P0302 or P0303 resets, go to next step. If related DTC P0301, P0302 or P0303 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S09346915962000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
4. Install a Spark Tester (J-26792) to related spark plug wire. Crank engine and observe spark tester. If a crisp, Blue spark is present, go to step 9 . If spark is weak or no spark is present, go to next step.
5. Remove and inspect related spark plug wire for carbon tracking and insulation damage. Repair as necessary. After repairs, go to step 12 . If wire is okay, go to next step.
6. Using DVOM, measure resistance of related spark plug wire. If resistance is 3000-6700 ohms per foot, go to next step. If resistance is greater than 6700 ohms per foot, replace spark plug wire. After repairs, go to step 12 .
7. Inspect distributor cap and rotor for moisture, cracks, carbon tracking, or poor terminal connection. Repair as necessary. After repairs, go to step 12 . If cap and rotor are okay, go to next step.
8. Check signal rotor located in distributor for damage. Ensure air gap is .008-.016" (.2-.4 mm). Adjust or repair as necessary. After repairs, go to step 12 . If signal rotor is okay, go to step 11 .
9. Remove and inspect related spark plug. Check for improper gap, cracked ceramic insulators or electrodes, carbon tracking, oil or fuel fouling, evidence of coolant, loose center electrode or terminal end, or missing platinum pads. Replace spark plug as necessary. After repairs, go to step 12 . If spark plug is okay, go to next step.
10. Check CKP sensor and signal rotor for damage. Repair as necessary. After repairs, go to step 12 . If CKP sensor and signal rotor are okay, go to «DIAGNOSTIC AIDS»(ref-189-S09346915962000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
11. Check for an engine mechanical problem. Check for faulty or incorrect camshaft, leaky or sticky valves or piston rings, excessive valve deposits, loose or worn rocker arms, weak valve springs, incorrect valve timing, vacuum leaks, leaking head gasket, and a loose or broken motor mount. Repair as necessary. After repairs, go to next step. If no mechanical problems are found, go to «DIAGNOSTIC AIDS»(ref-189-S09346915962000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
12. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

If any DTCs other than misfire DTCs P0300-P0303 are present, diagnose those DTCs first. Check for engine overheating, vacuum leaks or improper EGR system operation. Ensure PCV valve is operating properly. Check ignition system for a malfunction, including spark plugs, spark plug wires, ignition coil, and distributor. Ensure fuel pressure is correct and fuel injectors are operating properly. Check engine mechanical operation, including cylinder compression and valve adjustment function.

Check for conditions or faulty components which could cause an engine misfire. See appropriate TROUBLE SHOOTING - NO CODES article. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Start engine. If a misfire is present at idle, go to step 4 . If no misfire is present, go to next step.
3. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If related DTC P0301, P0302, P0303 or P0304 resets, go to next step. If related DTC P0301, P0302, P0303 or P0304 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S04981488392000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
4. Check for improperly operating or leaking PCV valve. Ensure PCV valve is correct for vehicle. Check for vacuum leak at intake manifold or gasket. Check for cracked, split or worn vacuum hose. Repair as necessary. After repairs, go to step 17 . If no problem is found, go to next step.
5. Install Spark Tester (J-26792) to related spark plug wire. Crank engine and observe spark tester. If a crisp, Blue spark is present, go to step 10 . If spark is weak or no spark is present, go to next step.
6. Remove and inspect related spark plug wire for carbon tracking and insulation damage. Repair as necessary. After repairs, go to step 17 . If wires are okay, go to next step.
7. Using DVOM, measure resistance of related spark plug wire. If resistance is 1200-3000 ohms per foot, go to next step. If resistance is greater than 3000 ohms per foot, replace spark plug wire. After repairs, go to step 17 .
8. Inspect related ignition coil for moisture, cracks, corrosion, carbon tracking, or poor terminal connection. Repair as necessary. After repairs, go to step 17 . If ignition coil is okay, go to next step.
9. Replace related ignition coil. After repairs, go to step 17 .
10. Remove and inspect related spark plug. Check for improper gap, cracked ceramic insulators or electrodes, carbon tracking, oil or fuel fouling, evidence of coolant, loose center electrode or terminal end, or missing platinum pads. Replace spark plug as necessary. After repairs, go to step 13 . If spark plug is okay, go to next step.
11. Turn ignition off. Disconnect related fuel injector electrical connector. Install Injector Test Light (J-34730-2B) on related fuel injector harness connector. Crank engine and observe test light. If test light flashes, go to next step. If test light does not flash, go to FUEL INJECTOR CIRCUIT (1.3L) under CIRCUIT TESTS in appropriate SYSTEM & COMPONENT TESTING article.
12. Check related fuel injector for proper operation. See FUEL INJECTOR COIL TEST - ENGINE COOLANT TEMPERATURE BETWEEN 50-95°F (1.3L) and FUEL INJECTOR BALANCE TEST (1.3L) under CIRCUIT TESTS in appropriate SYSTEM & COMPONENT TESTING article. Replace fuel injector as necessary. After repairs, go to step 17 . If fuel injector is okay, go to step 14 .
13. If spark plug is replaced because of fuel, oil or coolant fouling, go to next step. If spark plug is not replaced because of fuel, oil or coolant fouling, go to step 17 .
14. Check for an engine mechanical problem. Check for faulty or incorrect camshaft, leaky or sticky valves or piston rings, excessive valve deposits, loose or worn rocker arms, weak valve springs, incorrect valve timing, vacuum leaks, leaking head gasket, and a loose or broken motor mount. Repair as necessary. After repairs, go to step 17 . If no mechanical problems are found, go to next step.
15. Remove CKP sensor. Check CKP sensor for damage. Check for foreign material on sensor surface. Check for water or corrosion at electrical terminals. Repair as necessary. After repairs, go to step 17 . If CKP sensor is okay, go to next step.
16. Check CKP sensor signal rotor on crankshaft timing belt pulley for damaged teeth, foreign material or incorrect installation. Repair as necessary. After repairs, go to next step. If CKP sensor signal rotor is okay, go to «DIAGNOSTIC AIDS»(ref-189-S04981488392000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
17. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

If any DTCs other than misfire DTCs P0300-P0304 are present, diagnose those DTCs first. Check for engine overheating, vacuum leaks or improper EGR system operation. Ensure PCV valve is operating properly. Check ignition system for a malfunction, including spark plugs, spark plug wires, and ignition coil. Ensure fuel pressure is correct and fuel injectors are operating properly. Water in fuel may cause an intermittent misfire. Check engine mechanical operation, including cylinder compression and valve adjustment function.

Check for conditions or faulty components which could cause an engine misfire. See appropriate TROUBLE SHOOTING - NO CODES article. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Start engine. Using scan tool, monitor MISFIRE CURRENT CYLINDER parameter. If scan tool indicates a misfire in related cylinder, go to step 4 . If scan tool does not indicate a misfire in related cylinder, go to next step.
3. Turn ignition on, with engine off. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Operate vehicle within freeze frame conditions. If DTC P0301, P0302, P0303, or P0304 resets, go to next step. If DTC P0301, P0302, P0303, or P0304 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S00719212802000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
4. Install a Spark Tester (J-26792) to related spark plug wire. Crank engine and observe spark tester. If a crisp, Blue spark is present, go to step 8 . If spark is weak or no spark is present, go to next step.
5. Remove and inspect related spark plug wire for carbon tracking and insulation damage. Repair as necessary. Using DVOM, measure resistance of related spark plug wire. If resistance is 25,000 ohms, go to next step. If resistance is greater than 25,000 ohms, replace spark plug wire. After repairs, go to step 21 .
6. Inspect ignition coils for moisture, cracks, corrosion, carbon tracking, or poor terminal connection. Repair as necessary. After repairs, go to step 23 . If ignition coils are okay, go to next step.
7. Remove CKP sensor. Check CKP sensor signal rotor through sensor hole for damaged teeth, dents or nicks. Repair as necessary. After repairs, go to step 23 . If CKP sensor signal rotor is okay, go to step 19 .
8. Remove and inspect related spark plug. Check for improper gap, cracked ceramic insulators or electrodes, carbon tracking, oil or fuel fouling, evidence of coolant, loose center electrode or terminal end, or missing platinum pads. Replace spark plug as necessary. After repairs, go to step 23 . If spark plug is okay, go to next step.
9. Turn ignition off. Disconnect related fuel injector electrical connector. Install Injector Test Light (J-34730-2B) on related fuel injector harness connector. Crank engine and observe test light. If test light flashes, go to next step. If test light does not flash, go to step 11 .
10. Perform FUEL INJECTOR COIL TEST - ENGINE COOLANT TEMPERATURE BETWEEN 50-95°F (1.8L) and FUEL INJECTOR BALANCE TEST (1.8L) under CIRCUIT TESTS in appropriate SYSTEM & COMPONENT TESTING article. Replace fuel injector as necessary. After repairs, go to step 23 . If fuel injectors are okay, go to step 16 .
11. Disconnect fuel injector test light. Using test light connected to ground, probe related fuel injector harness connector ignition positive voltage circuit. See WIRING DIAGRAMS article. Turn ignition on, with engine off. If test light illuminates, go to next step. If test light does not illuminate, go to step 14 .
12. Using test light connected to battery voltage, probe related fuel injector harness connector injector control circuit. See WIRING DIAGRAMS article. Turn ignition on, with engine off. If test light illuminates, go to next step. If test light does not illuminate, go to step 15 .
13. Check for a short to ground in injector control circuit(s). Repair as necessary. After repairs, 23 . If circuit(s) is okay, go to step 20 .
14. Repair open or short in ignition positive voltage circuit to related fuel injector. After repairs, go to step 23 .
15. Check for an open in injector control circuit(s). Repair as necessary. After repairs, 23 . If circuit(s) is okay, go to step 20 .
16. Turn ignition off. Install fuel pressure gauge. See BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article. Start engine. Observe fuel pressure at idle with engine at normal operating temperature. If fuel pressure is 44-50 psi (3.0-3.5 kg/cm 2 ), go to next step. If fuel pressure is not as specified, go to BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
17. Check for alcohol or other contaminates in fuel. Check fuel type and quality. Replace contaminated fuel as necessary. After repairs, go to step 23 . If fuel is okay, go to next step.
18. Check for vacuum leaks at PCV valve, intake manifold gasket, vacuum lines, hoses and fittings. Repair as necessary. After repairs, go to step 23 . If no problem is found, go to step 22 .
19. Replace faulty ignition coil. After repairs, go to step 23 .
20. Replace PCM. Program PCM using required equipment. After replacing PCM, go to step 23 .
21. Replace faulty spark plug wire. After repairs, go to step 23 .
22. Check for an engine mechanical problem. Check for faulty or incorrect camshaft, leaky or sticky valves or piston rings, excessive valve deposits, loose or worn rocker arms, weak valve springs, incorrect valve timing, vacuum leaks, leaking head gasket, and a loose or broken motor mount. Repair as necessary. After repairs, go to next step. If no mechanical problems are found, go to «DIAGNOSTIC AIDS»(ref-189-S00719212802000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
23. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

If any DTCs other than misfire DTCs P0300-P0304 are present, diagnose those DTCs first. Check for engine overheating. Ensure PCV valve is operating properly. Check ignition system for a malfunction, including spark plugs, spark plug wires, and ignition coil. An intermittent can result from a defective crankshaft reluctor wheel. Remove CKP sensor and inspect reluctor wheel for porosity, nicks, dents or other damage.

Check for conditions or faulty components which could cause an engine misfire. See appropriate TROUBLE SHOOTING - NO CODES article. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Knock Sensor (KS) is located in rear of engine block. KS is a piezoelectric element used to detect engine knock (pre-ignition). When engine knock is present, KS sends an AC voltage signal to PCM. When PCM receives signal from KS, PCM will retard ignition timing. By retarding ignition timing, engine knock should no longer be detected. DTC P0325 will set when engine speed is 1200 RPM or more, VSS and TP sensor indicate vehicle is accelerating, and no KS signal is detected for more than 20 seconds.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer. PCM will default to maximum spark retard.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Operate vehicle within freeze frame conditions. If DTC P0325 resets, go to next step. If DTC P0325 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S35627516132000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
3. Turn ignition off. Disconnect KS electrical connector. Using DVOM connected to ground, probe KS harness connector terminal (KS input circuit). See WIRING DIAGRAMS article. Select AC frequency and push Hz button. Start engine. Operate at 4000 RPM. If frequency is 12.5 kHz, go to next step. If frequency is not 12.5 kHz, go to step 6 .
4. Turn ignition off. Reconnect KS connector. Disconnect PCM 16-pin connector. Using DVOM connected to ground, probe PCM 16-pin connector KS input circuit. See WIRING DIAGRAMS article. Select AC frequency and push Hz button. Start engine. Operate at 4000 RPM. If frequency is 12.5 kHz, go to step 7 . If frequency is not 12.5 kHz, go to next step.
5. Repair open or short in KS input circuit. Ensure KS terminal connection is okay. Repair as necessary. After repairs, go to step 8 .
6. Replace KS. After repairs, go to step 8 .
7. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
8. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Check for and correct any abnormal engine noises. Ensure KS is installed properly and is torqued to 29 ft. lbs. (39 N.m). Ensure no mechanical failures are inducing engine knock. See appropriate TROUBLE SHOOTING - NO CODES article. Ensure correct fuel octane level is being used.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Crankshaft Position (CKP) sensor is a magnetic generator type sensor. CKP sensor produces an alternating current signal which increases in both frequency and amplitude as engine RPM increases. CKP sensor sends a reference signal to PCM indicating crankshaft RPM and position. PCM uses CKP reference signal along with Camshaft Position (CMP) sensor signal, to calculate fuel injection pulse, determine TDC for ignition timing, and establish a starting point for ignition coil and injection sequencing. There will be not spark or fuel delivery if CKP sensor signal is not present. DTC P0335 will set when engine is cranking and no signal from CKP sensor signal for 2 seconds. When DTC sets, MIL will illuminate. PCM will record operating conditions at time of diagnostic failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If DTC P0335 resets, go to next step. If DTC P0335 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S03892954762000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
3. Turn ignition off. Disconnect CKP sensor electrical connector. Using DVOM, measure resistance of CKP sensor. If resistance is 360-460 ohms at 68°F (20°C), go to next step. If resistance is not 360-460 ohms at 68°F (20°C), go to step 8 .
4. Turn ignition off. Disconnect PCM 16-pin connector. Check for open or short in PCM 16-pin connector CKP sensor ignition reference high circuit and CKP sensor ignition reference low circuit. See WIRING DIAGRAMS article. Repair circuits as necessary. After repairs, go to step 10 . If circuits are okay, go to next step.
5. Check for poor terminal connections at PCM and CKP sensor. Repair as necessary. After repairs, go to step 10 . If terminal connections are okay, go to next step.
6. Remove CKP sensor. Check CKP sensor for damage. Check for foreign material on sensor surface. Check for water or corrosion at electrical terminals. Repair as necessary. After repairs, go to step 10 . If CKP sensor is okay, go to next step.
7. Check CKP sensor signal rotor on crankshaft timing belt pulley for damaged teeth, foreign material or incorrect installation. Repair as necessary. After repairs, go to step 10 . If CKP sensor signal rotor is okay, go to step 9 .
8. Replace CKP sensor. After repairs, go to step 10 .
9. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
10. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Remove CKP sensor from vehicle and connect DVOM to sensor terminals. Gently tap on pick-up end (magnetic end) of CKP sensor with a metal shaft or screwdriver. DVOM reading should change from 360-460 ohms to infinity, and then back to 360-460 ohms. CKP sensor performance may be affected by temperature. Check CKP sensor for water intrusion. Check CKP sensor signal rotor for foreign material or damaged teeth.

If DTC P0335 sets while driving and checks okay, check for inadequate CKP sensor circuit shielding. Check drain wire for a good ground. A short to ground in CKP sensor ignition reference low circuit will cause a faulty engine reference signal to PCM, but will not set DTC P0335.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Crankshaft Position (CKP) sensor is a magnetic generator type sensor. CKP sensor produces an alternating current signal which increases in both frequency and amplitude as engine RPM increases. CKP sensor sends a reference signal to PCM indicating crankshaft RPM and position. PCM uses CKP reference signal along with Camshaft Position (CMP) sensor signal, to calculate fuel injection pulse, determine TDC for ignition timing, and establish a starting point for ignition coil and injection sequencing. There will be not spark or fuel delivery if CKP sensor signal is not present. DTC P0335 will set when

1. No CKP sensor signal to PCM exists for 5 seconds during engine cranking.
2. No CKP sensor signal to PCM exists with engine speed at 600 RPM or more.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. If DTC P0335 and P0340 are both set, go to step 11 . If DTC P0335 and P0340 are not both set, go to next step.
3. If vehicle starts and runs, go to next step. If vehicle does not start and run, go to step 5 .
4. Turn ignition on, with engine off. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Operate vehicle within freeze frame conditions. If DTC P0335 resets, go to next step. If DTC P0335 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S28867655512000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
5. Turn ignition off. Disconnect CKP sensor electrical connector. Using DVOM, measure resistance of CKP sensor. If resistance is 1630-2740 ohms at 14-122°F (-10-50°C) or 2065-3225 ohms at 122-212°F (50-100°C), go to next step. If resistance is not as specified, go to step 13 .
6. Connect DVOM between CKP sensor terminals. Set DVOM to AC volt scale. Observe AC voltage while cranking engine. If voltage is 1.4-1.6 volts, go to next step. If voltage is not 1.4-1.6 volts, go to step 12 .
7. Turn ignition off. Disconnect PCM 26-pin connector. Connect DVOM between PCM 26-pin connector CKP sensor input circuit and CKP sensor ground circuit. See WIRING DIAGRAMS article. Observe AC voltage while cranking engine. If voltage is 1.4-1.6 volts, go to step 14 . If voltage is not 1.4-1.6 volts, go to next step.
8. Connect DVOM between ground and PCM 26-pin connector CKP sensor input circuit. See WIRING DIAGRAMS article. Observe AC voltage while cranking engine. If voltage is 0.9-1.1 volts, go to step 10 . If voltage is not 0.9-1.1 volts, go to next step.
9. Repair open or short in CKP sensor input circuit. After repairs, go to step 15 .
10. Repair open in CKP sensor ground circuit. After repairs, go to step 15 .
11. Repair open in CKP sensor and CMP sensor ground circuit between splice and PCM. After repairs, go to step 15 .
12. Remove CKP sensor. Check CKP sensor signal rotor for damaged teeth, foreign material or correct installation. Repair as necessary. After repairs, go to step 15 . If CKP sensor signal rotor is okay, go to next step.
13. Replace CKP sensor. After repairs, go to step 15 .
14. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
15. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

CKP sensor performance may be affected by temperature. Resistance should be 1630-2740 ohms at 14-122°F (-10-50°C) and 2065-3225 ohms at 122-212°F (50-100°C). An intermittent can result from a defective crankshaft reluctor wheel. Check CKP sensor signal rotor for foreign material or damaged teeth. If DTC P0335 sets while driving and checks okay, check for inadequate CKP sensor circuit shielding. Check drain wire for a good ground.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

When distributor shaft rotates, a fluctuating magnetic field is generated due to changes in air gap between Camshaft Position (CMP) sensor and distributor shaft signal rotor. As a result, a reference voltage is induced in CMP sensor. This ignition reference signal is sent to PCM. PCM uses these pulses as reference signals indicating engine speed and No. 1 cylinder identification.

DTC P0340 will set when no CMP sensor signal is generated with engine cranking for at least 2 seconds. When DTC sets, MIL will illuminate. PCM will record operating conditions at time of diagnostic failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions (crank engine if engine will not start). If DTC P0340 resets, go to next step. If DTC P0340 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S21939192542000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
3. Turn ignition off. Ensure vehicle is at ambient temperature. Disconnect distributor electrical connector. Using DVOM, measure resistance of CMP sensor (distributor side). If resistance is 185-275 ohms at 14-122°F (-10-50°C), go to next step. If resistance is not 185-275 ohms at 14-122°F (-10-50°C), go to step 11 .
4. Using DVOM set on AC volt scale, measure AC voltage of CMP sensor (distributor side) while cranking engine. If voltage is .1-.4 volt, go to next step. If voltage is not .1-.4 volt, go to step 8 .
5. Turn ignition off. Reconnect distributor electrical connector. Disconnect PCM 16-pin connector. Crank engine. Using DVOM, measure AC voltage of PCM 16-pin connector ignition reference high circuit and ignition reference low circuit. See WIRING DIAGRAMS article. If voltage is .1-.4 volt, go to step 10 . If voltage is not .1-.4 volt, go to next step.
6. Check for an open, short to ground, or short to voltage in ignition reference high circuit or ignition reference low circuit. Repair as necessary. After repairs, go to step 13 . If circuits are okay, go to next step.
7. Repair poor connection at distributor. After repairs, go to step 13 .
8. Check if CMP sensor air gap is .008-.016" (.2-.4 mm). See CAMSHAFT POSITION (CMP) SENSOR (1.0L) under ENGINE SENSORS & SWITCHES in appropriate SYSTEM & COMPONENT TESTING article. If air gap is as specified, go to step 11 . If air gap is not as specified, go to next step.
9. Adjust CMP sensor air gap. If engine starts and runs, go to step 13 . If engine does not start and run, go to step 11 .
10. Check for poor connection at PCM. Repair as necessary. After repairs, go to step 13 . If connection is okay, go to step 12 .
11. Replace CMP sensor. After repairs, go to step 13 .
12. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
13. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

If DTC P1500 is set, diagnosis DTC P1500 first. If starter motor does not operate normally a DTC P0340 may set, even though CMP sensor and its circuits are operating properly. If starter motor fails to operate normally and DTC P0340 is set, check starter motor first.

A loose or damaged CMP sensor could cause an intermittent DTC. A misaligned CMP sensor or improper air gap could set a DTC P0340 or an intermittent engine cranks but does not run condition. Resistance of CMP sensor will increase as engine temperatures increase.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

A signal rotor rotates with camshaft, and passes through the magnetic field of the Camshaft Position (CMP) sensor. A fluctuating magnetic field is generated when signal rotor passes CMP sensor. As a result, a reference voltage is induced in CMP sensor. This ignition reference signal is sent to PCM. PCM uses these pulses as reference signals identifying cylinders and performing misfire diagnosis. DTC P0340 will set when

1. No CMP sensor signal during engine cranking for at least 2 seconds.
2. No CMP sensor signal with engine running for at least 2 seconds.

When DTC sets, MIL will illuminate. PCM will record operating conditions at time of diagnostic failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If DTC P0340 resets, go to next step. If DTC P0340 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S39487071232000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
3. Turn ignition off. Disconnect CMP sensor electrical connector. Turn ignition on, with engine off. Using DVOM, measure voltage between ground and CMP sensor connector (harness side) CMP sensor ignition feed circuit. See WIRING DIAGRAMS article. If battery voltage is present, go to next step. If battery voltage is not present, go to step 8 .
4. Using DVOM, measure voltage between ground and CMP sensor connector (harness side) CMP sensor signal circuit. See WIRING DIAGRAMS article. If voltage is 4-5 volts, go to next step. If voltage is not 4-5 volts, go to step 7 .
5. Using test light connected to battery voltage, probe CMP sensor connector (harness side) CMP sensor ground circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 9 .
6. Turn ignition off. Remove CMP sensor. Reconnect CMP sensor electrical connector to sensor. Using DVOM connected to ground, backprobe PCM 16-pin connector CMP sensor signal circuit. See WIRING DIAGRAMS article. Turn ignition on, with engine off. Observe voltage while passing a metal (iron) object across face (magnet end) of CMP sensor. If voltage changes from 0-1 volt to 4-5 volts, go to step 12 . If voltage does not change as specified, go to step 10 .
7. Check for an open or short in CMP sensor signal circuit between CMP sensor and PCM. Repair as necessary. After repairs, go to step 13 . If circuit is okay, go to step 11 .
8. Repair open in CMP sensor ignition feed circuit. After repairs, go to step 13 .
9. Repair open or poor connection in CMP sensor ground circuit. After repairs, go to step 13 .
10. Replace CMP sensor. After repairs, go to step 13 .
11. Replace PCM. Program PCM using required equipment. After replacing PCM, go to step 13 .
12. Check CKP sensor signal rotor for damaged or missing teeth, or foreign material. Repair as necessary. After repairs, go to next step. If CKP sensor signal rotor is okay, go to «DIAGNOSTIC AIDS»(ref-189-S39487071232000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
13. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Check CMP sensor for damage. Check for foreign material on sensor surface. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Camshaft Position (CMP) sensor is a magnetic generator type sensor. CMP sensor produces an alternating current signal which increases in both frequency and amplitude as engine RPM increases. CMP sensor signal is used by PCM to determine optimum ignition timing, fuel delivery and misfire diagnosis. DTC P0340 will set when

1. No CMP sensor signal to PCM during engine cranking.
2. No CMP sensor signal to PCM with engine speed at 600 RPM or more.

When DTC sets, MIL will illuminate. PCM will record operating conditions at time of diagnostic failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. If vehicle does not start, or almost start and then stall immediately, go to step 10 . If vehicle starts, go to next step.
3. If vehicle starts and runs with MIL illuminated and DTC P0340 set, go to step 5 . If vehicle operation is not as specified, go to next step.
4. Turn ignition on, with engine off. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Operate vehicle within freeze frame conditions. If DTC P0340 resets, go to next step. If DTC P0340 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S40708480842000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
5. Turn ignition off. Disconnect CMP sensor electrical connector. Using DVOM, measure resistance of CMP sensor. If resistance is 835-1400 ohms at 14-122°F (-10-50°C) or 1060-1645 ohms at 122-212°F (50-100°C), go to next step. If resistance is not as specified, go to step 13 .
6. Connect DVOM between CMP sensor terminals. Set DVOM to AC volt scale. Observe AC voltage on DVOM and engine RPM on scan tool while cranking engine. If AC voltage and engine RPM are nearly equal, go to step 12 . If AC voltage and engine RPM are not nearly equal, go to next step.
7. Using test light connected to battery voltage, probe CMP sensor connector (harness side) CMP sensor ground circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 11 .
8. Turn ignition off. Disconnect PCM 26-pin connector. Remove CMP sensor input wire from PCM 26-pin connector. Reconnect PCM 26-pin connector with wire removed. Connect DVOM between ground and PCM 26-pin connector CKP sensor input circuit. See WIRING DIAGRAMS article. Observe AC voltage on DVOM and engine RPM on scan tool while cranking engine. If AC voltage and engine RPM are nearly equal, go to step 14 . If AC voltage and engine RPM are not nearly equal, go to next step.
9. Repair open or short in CMP sensor input circuit. After repairs, go to step 15 .
10. Repair open in CMP sensor and CKP sensor ground circuit between splice and sensor. After repairs, go to step 15 .
11. Repair open in CMP sensor ground circuit between splice and sensor. After repairs, go to step 15 .
12. Remove CMP sensor. Check CMP sensor signal rotor for damaged teeth, foreign material or correct installation. Repair as necessary. After repairs, go to step 15 . If CKP sensor signal rotor is okay, go to next step.
13. Replace CMP sensor. After repairs, go to step 15 .
14. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
15. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

CMP sensor performance may be affected by temperature. Resistance should be 835-1400 ohms at 14-122°F (-10-50°C) and 1060-1645 ohms at 122-212°F (50-100°C). CMP sensor performance can be checked with a DVOM and scan tool. Using DVOM, measure AC output voltage across CMP sensor terminals at different engine speeds. Compare scan tool value with DVOM reading. If readings are not nearly equal, check for a faulty sensor or signal rotor. If DTC P0340 sets while driving and checks okay, check for inadequate CMP sensor circuit shielding. Check drain wire for a good ground.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Exhaust Gas Recirculation (EGR) system controls level of oxides of nitrogen (NOx) emissions by recirculating exhaust gases back into combustion chamber. PCM will apply full manifold vacuum to EGR valve and monitor MAP sensor signal. PCM determines EGR flow to be faulty when monitored MAP sensor pressure change is too small or too large. DTC P0400 will set when

1. Fuel level is greater than 25 percent.
2. Intake air temperature is 14-122°F (-10-50°C).
3. Engine coolant temperature is 176-230°F (80-110°C).
4. Barometric pressure is greater than 11 psi (75 kPa).
5. Vehicle speed is greater than 20 MPH.
6. Engine speed is 1400-4000 RPM.
7. Intake pressure changes during steady driving after 240 seconds from engine start in EGR control mode. Throttle position change is less than .244 degrees in 16 firing events. Intake pressure difference diagnostic will run once per drive cycle for 2 seconds.
8. Intake pressure changes during deceleration after 290 seconds from engine start in fuel shut-off mode. Intake pressure difference diagnostic will run once per drive cycle for one second.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Start engine and allow it to reach normal operating temperature. If engine runs rough or idle is unstable, go to step 6 . If engine runs okay and idle is stable, go to next step.
3. Connect scan tool to DLC. Using scan tool, turn EGR by-pass valve on. If engine idle speed drops and engine runs rough, go to next step. If engine idle speed does not drop and engine runs okay, go to step 8 .
4. Place transaxle in Neutral and apply parking brake. Observe EGR valve diaphragm while accelerating engine. If EGR valve opens slightly, go to next step. If EGR valve does not open, go to step 15 .
5. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If DTC P0400 resets, go to step 2 . If DTC P0400 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S40373707442000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
6. Disconnect EGR valve vacuum hose. If engine idle stabilizes, go to next step. If engine idle does not stabilize, go to step 9 .
7. Connect a vacuum gauge to EGR valve vacuum supply hose and note reading. Disconnect EGR by-pass valve electrical connector. If vacuum gauge drops to zero in. Hg, go to step 25 . If vacuum reading does not drop, go to step 28 .
8. Using a rag or gloves for protection from heat, lift up on EGR valve diaphragm and observe engine performance. If engine idle speed drops and engine runs rough, go to step 10 . If engine idle speed does not drop and engine runs okay, go to next step.
9. Remove EGR valve. Check for sticking pintle, clogged passages, carbon deposits or a ruptured diaphragm. Repair as necessary. After repairs, go to step 30 . If no problems are found, go to step 23 .
10. Connect a vacuum gauge to EGR valve vacuum supply hose. Using scan tool, turn EGR by-pass valve on and observe vacuum gauge. If vacuum is 17-22 in. Hg, go to step 23 . If vacuum is not 17-22 in. Hg, go to next step.
11. Operate engine at normal operating temperature. Check for manifold vacuum from intake manifold vacuum port, leaking or damaged vacuum hoses, and clogged or restricted vacuum hoses or passages. Repair as necessary. After repairs, go to step 30 . If no problems are found, go to next step.
12. Turn ignition off. Disconnect EGR by-pass valve electrical connector. Using DVOM, measure resistance of EGR by-pass valve. If resistance is 28-36 ohms at 68°F (20°C), go to next step. If resistance is not 28-36 ohms at 68°F (20°C), go to step 28 .
13. Turn ignition on, with engine off. Using test light connected to ground, probe ignition feed circuit to EGR by-pass valve. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 26 .
14. Check for an open in EGR by-pass valve control circuit between EGR by-pass valve and PCM. Repair as necessary. After repairs, go to step 30 . If circuit is okay, go to step 29 .
15. Connect a vacuum gauge to EGR pressure transducer side of EGR solenoid vacuum valve. With engine running at normal operating temperature, increase engine speed to 2700 RPM. Using scan tool, turn EGR solenoid vacuum valve on. If vacuum is 5 in. Hg or more, go to next step. If vacuum is less than 5 in. Hg, go to step 19 .
16. Label pressure transducer vacuum hoses for installation reference. Unplug vacuum lines from transducer. Remove EGR pressure transducer. Place a finger over port "Q", and blow into port "P". If air passes through filter part of pressure transducer, go to next step. If air does not pass through filter, go to step 18 .
17. Connect a vacuum pump to EGR pressure transducer port "P", and plug port "Q". Apply vacuum to port "P". Vacuum pump gauge should indicate vacuum. Blow air into port "A". Vacuum pump gauge should indicate no vacuum. If vacuum holds and releases as specified, go to «DIAGNOSTIC AIDS»(ref-189-S40373707442000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article. If vacuum does not hold or release as specified, go to next step.
18. Replace EGR pressure transducer. After repairs, go to step 30 .
19. Check for ported vacuum to EGR solenoid vacuum valve. Check vacuum source and vacuum hoses for clogs and leaks. Repair as necessary. After repairs, go to step 30 . If vacuum is okay, go to next step.
20. Turn ignition off. Disconnect EGR solenoid vacuum valve electrical connector. Using DVOM, measure resistance of EGR solenoid vacuum valve. If resistance is 37-44 ohms at 68°F (20°C), go to next step. If resistance is not 37-44 ohms at 68°F (20°C), go to step 24 .
21. Turn ignition on, with engine off. Using test light connected to ground, probe ignition feed circuit to EGR solenoid vacuum valve. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 27 .
22. Check for an open or short in EGR solenoid vacuum valve control circuit between EGR solenoid vacuum valve and PCM. Repair as necessary. After repairs, go to step 30 . If circuit is okay, go to step 29 .
23. Replace EGR valve. After repairs, go to step 30 .
24. Replace EGR solenoid vacuum valve. After repairs, go to step 30 .
25. Check for a short in EGR by-pass valve control circuit between EGR by-pass valve and PCM. Repair as necessary. After repairs, go to step 30 . If circuit is okay, go to step 29 .
26. Repair open in ignition feed circuit to EGR by-pass valve. After repairs, go to step 30 .
27. Repair open in ignition feed circuit to EGR solenoid vacuum valve. After repairs, go to step 30 .
28. Replace EGR by-pass valve. After repairs, go to step 30 .
29. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
30. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Check all vacuum hoses for poor connections, leaks, deterioration, restrictions or clogs, or incorrect routing. Check for EGR valve stuck open or closed, or clogged. Check for EGR pressure transducer malfunction. Check for malfunctions in EGR solenoid vacuum valve or EGR by-pass valve.

Ensure correct PCM is installed in vehicle. An incorrect PCM can cause a DTC P0400 to set. California certified vehicles do not have an EGR system and will set a DTC P0400 if a Federal or Canadian certified PCM is used.

DTC P0400 can be set when expected change in MAP sensor input is not within specified value during operation of EGR by-pass valve. Any condition that can affect MAP sensor readings should be inspected.

Check for a poor PCM electrical connection. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Three-Way Catalyst (TWC) is used to control carbon monoxide (CO), hydrocarbons (HC) and oxides of nitrogen (NOx) exhaust emissions. TWC promotes a chemical reaction which oxidizes HC and CO, converting them to water vapor and carbon dioxide. NOx emissions are converted to nitrogen. PCM has the ability to monitor catalyst efficiency by using HO2S-1 and HO2S-2. HO2S-1 produces an output signal indicating oxygen content in exhaust gases entering Three-Way Catalyst (TWC). HO2S-2 produces an output signal indicating oxygen storage capacity of TWC. A comparison reading from sensors determines catalyst's ability to convert exhaust gases efficiently. If TWC is operating efficiently, HO2S-1 will be far more active than HO2S-2. DTC P0420 will set when

1. Fuel level is greater than 25 percent.
2. Engine coolant temperature is 158-230°F (70-110°C).
3. Intake air temperature is 14-158°F (-10-70°C).
4. Barometric pressure is greater than 11 psi (75 kPa).
5. Engine is operating in closed loop.
6. Calculated load value is 26-80 percent.
7. Delay time average of HO2S-2 response is not within specification.
8. Conditions are present for 45 seconds.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of diagnostic failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Check for HO2S DTCs and diagnose those DTCs first. If DTC P0131, P0132, P0133, P0134, P0135, P0136, or P0141 is set, diagnose DTC(s). If no other DTC is set, go to next step.
3. Connect scan tool to DLC. Start engine and run until normal operating temperature is reached. Ensure engine is operating in closed loop. Run engine at 2500-3000 RPM for 3 minutes. Using scan tool, monitor HO2S-1 and HO2S-2 signals. If HO2S-1 signal is as active as HO2S-2 signal, go to step 5 . If HO2S-1 signal is not as active as HO2S-2 signal, go to next step.
4. Turn ignition on, with engine off. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Operate vehicle within freeze frame conditions. If DTC P0420 resets, go to next step. If DTC P0420 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S40708480842000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
5. Check TWC for severe discoloration caused by excessive temperatures. Check for dents, holes or an internal rattle, indicating damaged catalyst. Ensure TWC meets manufacturer specifications. If any problems are found, go to step 8 . If no problems are found, go to next step.
6. Check exhaust system for loose or missing hardware, leaks, or damage. Repair as necessary. After repairs, go to step 9 . If exhaust system is okay, go to next step.
7. Check HO2S-2 for proper installation and for road damage. Ensure HO2S-2 wire harness is not contacting exhaust system. Repair as necessary. After repairs, go to step 9 . If HO2S-2 is okay, go to next step.
8. Locate and repair cause of TWC failure. Replace TWC. After repairs, go to step 10 .
9. Start engine and run until normal operating temperature is reached. Ensure engine is operating in closed loop. Run engine at 2500-3000 RPM for 3 minutes. Using scan tool, monitor HO2S-1 and HO2S-2 signals. If HO2S-1 signal is as active as HO2S-2 signal, go to «DIAGNOSTIC AIDS»(ref-189-S11903775882000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article. If HO2S-1 signal is not as active as HO2S-2 signal, go to next step.
10. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Check for exhaust system leaks, malfunctioning TWC, faulty oxygen sensors or fuel system malfunction. Repair all HO2S related DTCs first.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Three-Way Catalyst (TWC) is used to control carbon monoxide (CO), hydrocarbons (HC) and oxides of nitrogen (NOx) exhaust emissions. TWC promotes a chemical reaction which oxidizes HC and CO, converting them to water vapor and carbon dioxide. NOx emissions are converted to nitrogen. PCM monitors this process using a Heated Oxygen Sensor-2 (HO2S-2), located after TWC. PCM compares HO2S-2 signal with Heated Oxygen Sensor-1 (HO2S-1), located before TWC. If TWC is operating correctly, HO2S-2 signal will be much less active than HO2S-1. When both oxygen sensor signals change at similar rates, deteriorated catalyst performance is indicated.

DTC P0420 will set when HO2S-2 and HO2S-1 signals change at similar rates with engine operating in closed loop, engine coolant temperature greater than 158°F (70°C), and engine speed is 2500-3000 for at least 3 minutes while driving at certain vehicle speeds.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of diagnostic failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Check for HO2S DTCs and diagnose those DTCs first. If DTC P0130, P0133, P0135, P0136, or P0141 is set, diagnose DTC(s). If no other DTC is set, go to next step.
3. Connect scan tool to DLC. Start engine and run until normal operating temperature is reached. Ensure engine is operating in closed loop. Run engine at 2500-3000 RPM for 3 minutes. Using scan tool, monitor HO2S-1 and HO2S-2 signals. If HO2S-1 signal is as active as HO2S-2 signal, go to step 5 . If HO2S-1 signal is not as active as HO2S-2 signal, go to next step.
4. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Operate vehicle within freeze frame conditions. If DTC P0420 resets, go to next step. If DTC P0420 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S14617491872000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
5. Check TWC for severe discoloration caused by excessive temperatures. Check for dents, holes or an internal rattle, indicating damaged catalyst. Ensure TWC meets manufacturer specifications. If any problems are found, go to step 8 . If no problems are found, go to next step.
6. Check exhaust system for loose or missing hardware, leaks, or damage. Repair as necessary. After repairs, go to step 9 . If exhaust system is okay, go to next step.
7. Check HO2S-2 for proper installation and for road damage. Ensure HO2S-2 wire harness is not contacting exhaust system. Repair as necessary. After repairs, go to step 9 . If HO2S-2 is okay, go to next step.
8. Locate and repair cause of TWC failure. Replace TWC. After repairs, go to step 10 .
9. Start engine and run until normal operating temperature is reached. Ensure engine is operating in closed loop. Run engine at 2500-3000 RPM for 3 minutes. Using scan tool, monitor HO2S-1 and HO2S-2 signals. If HO2S-1 signal is as active as HO2S-2 signal, go to step «DIAGNOSTIC AIDS»(ref-189-S14617491872000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article. If HO2S-1 signal is not as active as HO2S-2 signal, go to next step.
10. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Check for exhaust system leaks, malfunctioning TWC, faulty oxygen sensors or fuel system malfunction. Repair all HO2S related DTCs first.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

EVAP system includes fuel tank, EVAP canister vent solenoid, fuel tank pressure sensor, fuel tank pressure control valves, EVAP tank pressure control solenoid vacuum valve, fuel lines and hoses, vapor and purge lines, fuel cap, EVAP canister, and EVAP canister purge solenoid valve. When Evaporation (EVAP) canister purge solenoid valve and EVAP canister vent solenoid are turned on, engine vacuum is applied to entire EVAP system. PCM monitors amount of vacuum decay based on fuel tank pressure sensor input. DTC P0440 or P0455 will set when

1. Fuel level is 25-75 percent.
2. Engine coolant temperature is 158-230°F (70-110°C).
3. Intake air temperature is 14-158°F (-10-70°C).
4. Barometric pressure is greater than 11 psi (75 kPa).
5. A change in fuel tank pressure (DTC P0440).
6. Purge accumulation time is greater than 200 seconds (DTC P0455).

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of diagnostic failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. If other EVAP DTCs than P0440 or P0455 are set, diagnose DTC(s). If no other EVAP DTCs are set, go to next step.
3. Check vacuum hoses for proper routing. Check for missing or damaged components. Ensure wiring harness connections to EVAP components are clean and tight. Check fuel filler cap for a tight seal. If a problem is found, go to step 40 . If no problems are found, go to next step.
4. Check for manifold vacuum at EVAP canister purge solenoid valve. If a problem is found, repair as necessary, go to step 40 . If no problems are found, go to next step.
5. Turn ignition on, with engine off. Disconnect EVAP canister purge solenoid valve vacuum hoses at intake manifold and EVAP canister. Blow air into EVAP canister purge solenoid valve vacuum hose disconnected from EVAP canister. Air should not pass through EVAP canister purge solenoid valve and exit out intake manifold hose. Using scan tool, command EVAP canister purge solenoid valve on and adjust duty cycle to 100 percent. Blow air into EVAP canister purge solenoid valve vacuum hose disconnected from EVAP canister. Air should pass through EVAP canister purge solenoid valve and exit out intake manifold hose. If airflow through EVAP canister purge solenoid valve is as described, go to step 8 . If airflow through EVAP canister purge solenoid valve is not as described, go to next step.
6. Turn ignition on, with engine off. Using test light connected to ground, probe EVAP canister purge solenoid valve connector (harness side) ignition positive voltage circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 33 .
7. Using test light connected to battery voltage, probe EVAP canister purge solenoid valve connector (harness side) control circuit. See WIRING DIAGRAMS article. Using scan tool, command EVAP canister purge solenoid valve on. Adjust duty cycle from zero percent to 100 percent while monitoring test light. If test light flashes near zero percent and illuminates steady near 100 percent duty cycle, go to step 32 . If test light does not flash or illuminate as specified, go to step 36 .
8. Turn ignition on, with engine off. Remove fuel filler cap. Install Gas Cap Adapter (J-41415-30). Connect EVAP Pressure/Purge Diagnostic Station (J-41413) to gas cap adapter. Using scan tool, command EVAP canister vent solenoid off. Using EVAP pressure/purge diagnostic station, pressurize EVAP system to 15 in. H 2 O. Monitor pressure on diagnostic station gauge. Turn rotary switch on station to HOLD position. Observe EVAP pressure gauge. If pressure decreases to less than 10 in. H 2 O within 2 minutes, go to next step. If pressure holds at 10 in. H 2 O or more, go to step 10 .
9. Using scan tool, command EVAP canister vent solenoid on. Using EVAP pressure/purge diagnostic station, pressurize EVAP system to 15 in. H 2 O. Monitor pressure on diagnostic station gauge. Turn rotary switch on station to HOLD position. Observe EVAP pressure gauge. If pressure decreases to less than 10 in. H 2 O within 2 minutes, go to step 11 . If pressure holds at 10 in. H 2 O or more, go to step 16 .
10. With EVAP system still pressurized to 10 in. H 2 O, turn EVAP tank pressure control solenoid vacuum valve on and observe EVAP pressure gauge. If pressure decreases to zero, go to next step. If pressure does not decrease to zero, go to step 15 .
11. Using scan tool, command EVAP canister vent solenoid on. Using EVAP pressure/purge diagnostic station, attempt to pressurize EVAP system to 30 in. H 2 O. Using Ultrasonic Leak Detector (J-41416), check for any leaks in EVAP system. Lower fuel tank as necessary to inspect EVAP connections on top of tank. If leaks are present, go to next step. If no leaks are present, go to step 13 .
12. Replace any leaking or faulty EVAP control system components. Replace any leaking EVAP lines or hoses. Repair or replace leaking or stuck open EVAP canister vent solenoid. After repairs, go to step 40 .
13. Turn ignition off. Remove fuel filler cap. Turn ignition on, with engine off. Using scan tool, monitor fuel tank pressure sensor parameter. If fuel tank pressure sensor value is 0.0-0.5 in. H 2 O, go to next step. If fuel tank pressure sensor value is not 0.0-0.5 in. H 2 O, go to DTC P0450. See «DTC P0450: EVAPORATIVE EMISSION (EVAP) SYSTEM PRESSURE SENSOR CIRCUIT (1.0L & 1.3L)»(ref-189-S20917474532000030800000) .
14. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Operate vehicle within freeze frame conditions. If DTC P0440 or P0455 resets, go to step 19 . If DTC P0440 or P0455 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S40708480842000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
15. Turn ignition on, with engine off. Using scan tool, command EVAP canister vent solenoid on and off while listening for solenoid to click on and off. If solenoid can be heard clicking on and off, go to step 25 . If solenoid can not be heard clicking on and off, go to step 19 .
16. Check for a short to ground in control circuit between EVAP tank pressure control solenoid vacuum valve and PCM. Repair as necessary. After repairs, go to step 40 . If circuit is okay, go to next step.
17. Remove fuel tank. Remove both fuel tank pressure control valves. Blow hard through tank side port of fuel tank pressure control valve. If air flows through valve to canister port side, go to next step. If air does not pass through valve, go to step 35 .
18. Gently blow air through canister side port of fuel tank pressure control valve. Air should flow easily through valve to tank port side. If airflow is as described, go to step 27 . If air does not flow as described, go to step 35 .
19. Remove rear seat cushion. Disconnect fuel tank EVAP solenoid harness electrical connector C311. Turn ignition on, with engine off. Connect a test light between ignition positive voltage terminal and EVAP canister vent solenoid control circuit terminal of connector C311 (body harness side). See WIRING DIAGRAMS article. Using scan tool, command EVAP canister vent solenoid on and off while observing test light. If test light illuminates only when solenoid is commanded on, go to step 21 . If test light does not illuminate, go to next step.
20. Check for an open in EVAP canister vent solenoid ignition positive voltage circuit. Check for an open or short in EVAP canister vent solenoid control circuit between EVAP canister vent solenoid and PCM. Repair as necessary. After repairs, go to step 40 . If circuits are okay, go to step 39 .
21. Remove fuel tank. Check EVAP system lines, hoses and connections for any blockage or restrictions. Repair as necessary. After repairs, go to step 40 . If lines, hoses and connections are okay, go to next step.
22. Remove EVAP canister vent solenoid. Using a hand-held vacuum pump, apply 15 in. Hg of vacuum to canister side of EVAP canister vent solenoid. If solenoid holds vacuum, go to step 34 . If solenoid does not hold vacuum, go to next step.
23. Apply 12 volts to EVAP canister vent solenoid. Using a hand-held vacuum pump, apply 15 in. Hg of vacuum to canister side of EVAP canister vent solenoid. If solenoid holds vacuum, go to next step. If solenoid does not hold vacuum, go to step 34 .
24. Check for an open or short in EVAP canister vent solenoid wiring harness between EVAP canister vent solenoid and connector C311 (body harness). Repair as necessary. After repairs, go to step 40 . If wiring harness is okay, go to step 31 .
25. Remove rear seat cushion. Disconnect fuel tank EVAP solenoid harness electrical connector C311. Turn ignition on, with engine off. Connect a test light between ignition positive voltage terminal and EVAP tank pressure control solenoid vacuum valve control circuit terminal of connector C311 (body harness side). See WIRING DIAGRAMS article. Using scan tool, command EVAP tank pressure control solenoid vacuum valve on and off while observing test light. If test light illuminates only when solenoid is commanded on, go to step 26 . If test light does not illuminate, go to step 30 .
26. Remove fuel tank. Check EVAP tank pressure control solenoid vacuum valve lines, hoses and connections for any blockage or restrictions. Repair as necessary. After repairs, go to step 40 . If lines, hoses and connections are okay, go to next step.
27. Remove EVAP tank pressure control solenoid vacuum valve. Blow through the side port of EVAP tank pressure control solenoid vacuum valve. If air flows through valve to the top port of EVAP tank pressure control solenoid vacuum valve, go to step 38 . If air does not pass through valve, go to next step.
28. Apply 12 volts to EVAP tank pressure control solenoid vacuum valve. Blow through the side port of EVAP tank pressure control solenoid vacuum valve. If air flows through valve to the top port of EVAP tank pressure control solenoid vacuum valve, go to next step. If air does not pass through valve, go to step 38 .
29. Repair open or short in EVAP tank pressure control solenoid vacuum valve wiring harness between EVAP tank pressure control solenoid vacuum valve and connector C311 (body harness). After repairs, go to step 40 .
30. Check for an open in EVAP tank pressure control solenoid vacuum valve ignition positive voltage circuit. Check for an open or short in EVAP tank pressure control solenoid vacuum valve control circuit between EVAP tank pressure control solenoid vacuum valve and PCM. Repair as necessary. After repairs, go to step 40 . If circuits are okay, go to step 39 .
31. Disconnect EVAP canister vapor hose at fuel limiter vent valve. Disconnect other 3 hoses from EVAP vapor canister. Blow air into hose connected to EVAP canister tank port. Air should flow through canister and exist other 3 ports. If air flows through canister and exists other 3 ports, go to «DIAGNOSTIC AIDS»(ref-189-S40708480842000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article. If air does not flow as specified, go to next step.
32. Replace EVAP canister. After repairs, go to step 40 .
33. Repair open in ignition positive voltage circuit between EVAP canister purge solenoid valve and main relay. After repairs, go to step 40 .
34. Replace EVAP canister vent solenoid. After repairs, go to step 40 .
35. Replace faulty fuel tank pressure control valve. After repairs, go to step 40 .
36. Check for an open or short in EVAP canister purge solenoid valve control circuit between EVAP canister purge solenoid valve and PCM. Repair as necessary. After repairs, go to step 40 . If circuit is okay, go to step 39 .
37. Replace EVAP canister purge solenoid valve. After repairs, go to step 40 .
38. Replace EVAP tank pressure control solenoid vacuum valve. After repairs, go to step 40 .
39. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
40. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

If a reasonable vacuum cannot be sustained for a specific time, a small leak will be indicated and DTC will set. A leak can be caused by any of the following conditions

1. Damaged or disconnected source vacuum hose.
2. Damaged or leaking EVAP purge or vent hoses.
3. Damaged or leaking fuel tank vapor hose.
4. Faulty fuel tank pressure control valve.
5. Faulty or loose fuel cap.
6. Fuel level sensor malfunction.
7. Fuel tank pressure sensor malfunction.
8. Cracked or punctured EVAP canister.
9. Leaking or faulty EVAP canister purge solenoid valve.
10. Leaking or faulty EVAP fuel tank pressure control solenoid vacuum valve.
11. Leaking or faulty EVAP canister vent solenoid.
12. Leaking fuel sender assembly "O" ring.
13. Leaking fuel tank or fuel filler neck.

Perform an inspection of all EVAP system components and vacuum hoses. See underhood vehicle emission control information label for component identification and vacuum hose routing.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

EVAP system includes fuel tank, fuel tank pressure sensor, EVAP pressure switching solenoid, fuel lines and hoses, vapor and purge lines, fuel cap, EVAP canister, and EVAP canister purge solenoid valve. PCM monitors positive and negative pressure in fuel tank using the fuel tank pressure sensor. PCM turns on the EVAP pressure switching solenoid to monitor positive and negative pressure in EVAP system under certain engine operating conditions. PCM detects any abnormal conditions by the fluctuation of this pressure. DTC P0440 will set when

1. Fuel level is 25-75 percent.
2. Engine coolant temperature is greater than 158°F (70°C).
3. Fuel tank pressure sensor reads atmospheric pressure.
4. Vehicle is driven for 20 minutes.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of diagnostic failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Retrieve DTCs. If DTC P0450 is set, diagnose DTC. See «DTC P0450: EVAPORATIVE EMISSION (EVAP) SYSTEM PRESSURE SENSOR CIRCUIT (1.8L)»(ref-189-S08121452172000030800000) . If DTC P0450 is not set, go to next step.
3. If DTC P0441 or P0446 is set along with DTC P0440, diagnose DTC(s). See «DTC P0441: EVAPORATIVE EMISSION (EVAP) SYSTEM INCORRECT PURGE FLOW (1.8L)»(ref-189-S24230170162000030800000) or «DTC P0446: EVAPORATIVE EMISSION (EVAP) VENT CONTROL SYSTEM (1.8L)»(ref-189-S24230170162000030800000) .
4. Check the following components for cracks, leaks or damage. Fuel tank filler cap. Fuel tank pressure sensor. Fuel tank. EVAP canister. Fuel supply system lines, hoses and fittings. Repair as necessary. After repairs, go to step 23 . If components are okay, go to next step.
5. Remove fuel filler cap. Install Gas Cap Adapter (J-41415-30). Connect EVAP Pressure/Purge Diagnostic Station (J-41413) to gas cap adapter. Using EVAP pressure/purge diagnostic station, pressurize EVAP system to 4.5-5.5 in. H 2 O. Turn rotary switch on station to HOLD position. If pressure holds at 4.5-5.5 in. H 2 O for 2 minutes, go to next step. If pressure does not hold at 4.5-5.5 in. H 2 O, go to step 18 .
6. Loosen fuel filler cap. Remove left kick panel. Turn ignition on, with engine off. Using DVOM connected to ground, backprobe fuel tank pressure sensor input circuit (Blue wire) at connector C221. See WIRING DIAGRAMS article. If voltage is 3-3.6 volts, go to next step. If voltage is not 3-3.6 volts, go to step 9 .
7. Connect scan tool to DLC. Using scan tool, select EVAP pressure switching solenoid output control feature. Using EVAP pressure/purge diagnostic station, pressurize EVAP system to 4.5-5.5 in. H 2 O. Turn rotary switch on station to HOLD position. Using scan tool, command EVAP pressure switching solenoid on. Using DVOM connected to ground, backprobe fuel tank pressure sensor input circuit (Blue wire) at connector C221. See WIRING DIAGRAMS article. If voltage is 4.2-4.6 volts, go to step 17 . If voltage is not 4.2-4.6 volts, go to next step.
8. Check EVAP pressure switching solenoid for leaks. Check for leaks at 3 vacuum/vapor hoses connected to EVAP pressure switching solenoid. Repair or replace as necessary. After repairs, go to step 23 . If no leaks are found, go to step 18 .
9. Disconnect vapor pressure supply hose to fuel tank pressure sensor. Using DVOM, measure voltage of fuel tank pressure sensor input circuit (Blue wire) at connector C221. See WIRING DIAGRAMS article. If voltage is 3-3.6 volts, go to next step. If voltage is not 3-3.6 volts, go to step 11 .
10. Repair cause of trapped vapor pressure to fuel tank pressure sensor. Check for pinched, crushed or restricted EVAP lines and hoses. Check for blocked or restricted EVAP components. Check for faulty EVAP solenoids or EVAP canister. Repair as necessary. After repairs, go to step 23 .
11. Turn ignition off. Disconnect fuel tank pressure sensor electrical connector. Turn ignition on, with engine off. Using DVOM, measure voltage of fuel tank pressure sensor reference voltage circuit at fuel tank pressure sensor connector (harness side). See WIRING DIAGRAMS article. If voltage is 5 volts, go to next step. If voltage is not 5 volts, go to step 13 .
12. Using DVOM, measure voltage of fuel tank pressure sensor input circuit at fuel tank pressure sensor connector (harness side). See WIRING DIAGRAMS article. If voltage is 4.9 volts, go to step 15 . If voltage is not 4.9 volts, go to step 14 .
13. Check for an open or short in fuel tank pressure sensor reference voltage circuit between fuel tank pressure sensor and PCM. Repair as necessary. After repairs, go to step 23 . If circuit is okay, go to step 22 .
14. Check for an open or short in fuel tank pressure sensor input circuit between fuel tank pressure sensor and PCM. Ensure fuel tank pressure sensor input circuit is not shorted to sensor ground circuit. Repair as necessary. After repairs, go to step 23 . If circuit is okay, go to step 22 .
15. Using test light connected to battery voltage, probe fuel tank pressure sensor connector ground circuit (harness side). See WIRING DIAGRAMS article. If test light illuminates, go to step 21 . If test light does not illuminate, go to next step.
16. Check for an open in fuel tank pressure sensor ground circuit between fuel tank pressure sensor and PCM. Repair as necessary. After repairs, go to step 23 . If circuit is okay, go to step 22 .
17. Turn ignition on, with engine off. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Operate vehicle within freeze frame conditions. If DTC P0440 resets, go to step 19 . If DTC P0440 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S10982254312000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
18. Remove ORVR vent line from EVAP canister and plug hose. Remove EVAP vapor line from EVAP canister and plug hose. Using EVAP pressure/purge diagnostic station, attempt to pressurize EVAP system to 30 in. H 2 O and hold. Using Ultrasonic Leak Detector (J-41416), check for any leaks in EVAP system. Lower fuel tank as necessary to inspect condition of fill limiter vent valve and rollover valve on top of tank. Also, check fuel sender assembly for a correct seal. If any EVAP or fuel supply system leaks are present, go to step 20 . If no leaks are present, go to next step.
19. Replace faulty/leaking EVAP canister. After repairs, go to step 22 .
20. Repair or replace leaking EVAP system or fuel tank component. After repairs, go to step 23 .
21. Replace fuel tank pressure sensor. After repairs, go to step 23 .
22. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
23. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

If DTCs P0441, P0446 or P0450 are also set, diagnose those DTCs first. A faulty or erratic fuel tank pressure sensor can cause DTC to set. Check for problems in any of the following components or for any of the following conditions

1. Fuel tank pressure sensor.
2. Loose or faulty fuel filler cap.
3. Faulty or leaking fuel limiter vent valve.
4. Leak in fuel tank.
5. Faulty or leaking EVAP canister.
6. Damaged or leaky hoses, lines or fittings between fuel tank, fuel tank pressure sensor and EVAP canister.

Perform an inspection of all EVAP system components and vacuum hoses. See underhood vehicle emission control information label for component identification and vacuum hose routing.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

EVAP system includes fuel tank, fuel tank pressure sensor, EVAP pressure switching solenoid, fuel lines and hoses, vapor and purge lines, fuel cap, EVAP canister, and EVAP canister purge solenoid valve. PCM monitors positive and negative pressure in fuel tank using the fuel tank pressure sensor. PCM turns on the EVAP pressure switching solenoid to monitor positive and negative pressure in EVAP system under certain engine operating conditions. PCM detects any abnormal conditions by the fluctuation of this pressure.

DTC P0441 will set when pressure in EVAP canister does not drop during purge control, or pressure in EVAP canister is very low compared with atmospheric pressure during purge cut-off.

DTC P0446 will set when

1. EVAP pressure switching solenoid is off. Pressure in EVAP canister is not within expected values.
2. EVAP pressure switching solenoid is on. Pressure in fuel tank is not within expected values.
3. Pressure in EVAP canister is equal to atmospheric pressure after purge cut-off (EVAP canister purge solenoid valve is off).

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of diagnostic failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Retrieve DTCs. If DTC P0450 is set, diagnose DTC. See «DTC P0450: EVAPORATIVE EMISSION (EVAP) SYSTEM PRESSURE SENSOR CIRCUIT (1.8L)»(ref-189-S08121452172000030800000) .
3. Check the following components for cracks, leaks or damage. Fuel tank filler cap. Fuel tank pressure sensor. Fuel tank. EVAP canister. Fuel supply system lines, hoses and fittings. Repair as necessary. After repairs, go to step 43 . If components are okay, go to next step.
4. Disconnect EVAP canister purge solenoid valve electrical connector. Turn ignition on, with engine off. Using test light connected to ground, probe EVAP canister purge solenoid valve connector (harness side) ignition positive voltage circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 7 .
5. Disconnect both vacuum hoses from EVAP canister purge solenoid valve. Blow air into lower port of EVAP canister purge solenoid valve. Air should not pass through valve and out upper port. Using a fused jumper wire, connect battery voltage to EVAP canister purge solenoid valve ignition positive voltage circuit and ground EVAP canister purge solenoid valve control circuit. See WIRING DIAGRAMS article. Blow air into lower port of EVAP canister purge solenoid valve. Air should pass through valve and out upper port. If air flows as specified, go to next step. If air does not flow as specified, go to step 34 .
6. Turn ignition on, with engine off. Using test light connected to battery voltage, probe EVAP canister purge solenoid valve connector (harness side) control circuit. See WIRING DIAGRAMS article. If test light illuminates, go to step 40 . If test light does not illuminate, go to step 8 .
7. Repair open in EVAP canister purge solenoid valve ignition positive voltage circuit between EVAP canister purge solenoid valve and PCM. After repairs, go to step 43 .
8. Using DVOM, measure resistance of EVAP canister purge solenoid valve. If resistance is 27-33 ohms at 68°F (20°C), go to next step. If resistance is not 27-33 ohms at 68°F (20°C), go to step 36 .
9. Loosen fuel filler cap. Remove left kick panel. Turn ignition on, with engine off. Using DVOM connected to ground, backprobe fuel tank pressure sensor input circuit (Blue wire) at connector C221. See WIRING DIAGRAMS article. If voltage is 3-3.6 volts, go to next step. If voltage is not 3-3.6 volts, go to step 19 .
10. Remove fuel filler cap. Install Gas Cap Adapter (J-41415-30). Connect EVAP Pressure/Purge Diagnostic Station (J-41413) to gas cap adapter. Using EVAP pressure/purge diagnostic station, pressurize EVAP system to 4.5-5.5 in. H 2 O. Turn rotary switch on station to HOLD position. If pressure holds at 4.5-5.5 in. H 2 O for 2 minutes, go to step 12 . If pressure does not hold at 4.5-5.5 in. H 2 O, go to next step.
11. Check EVAP pressure switching solenoid for leaks. Check for leaks at 3 vacuum/vapor hoses connected to EVAP pressure switching solenoid. Repair or replace as necessary. After repairs, go to step 43 . If no leaks are found, go to step 27 .
12. Connect scan tool to DLC. Using scan tool, select EVAP pressure switching solenoid output control feature. Using EVAP pressure/purge diagnostic station, pressurize EVAP system to 4.5-5.5 in. H 2 O. Turn rotary switch on station to HOLD position. Using scan tool, command EVAP pressure switching solenoid on. Using DVOM connected to ground, backprobe fuel tank pressure sensor input circuit (Blue wire) at connector C221. See WIRING DIAGRAMS article. If voltage is 4.2-4.6 volts, go to next step. If voltage is not 4.2-4.6 volts, go to step 14 .
13. Remove ORVR vent line from EVAP canister and plug hose. Remove EVAP vapor line from EVAP canister and plug hose. Using a section of vacuum pipe, connect EVAP vapor line and purge line together. Using EVAP pressure/purge diagnostic station, attempt to pressurize EVAP system to 30 in. H 2 O and hold. Using Ultrasonic Leak Detector (J-41416), check for any leaks in EVAP system. Lower fuel tank as necessary to inspect condition of fill limiter vent valve and rollover valve on top of tank. Also, check fuel sender assembly for a correct seal. If any EVAP or fuel supply system leaks are present, go to step 29 . If no leaks are present, go to step 37 .
14. Disconnect EVAP pressure switching solenoid electrical connector. Turn ignition on, with engine off. Using test light connected to ground, probe EVAP pressure switching solenoid connector (harness side) ignition positive voltage circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 18 .
15. Using test light connected to battery voltage, probe EVAP pressure switching solenoid connector (harness side) control circuit. See WIRING DIAGRAMS article. Using scan tool, command EVAP pressure switching solenoid on. If test light illuminates when solenoid is commanded on, go to next step. If test light does not illuminate when solenoid is commanded on, go to step 17 .
16. Reconnect EVAP pressure switching solenoid electrical connector. Disconnect 3 vacuum hoses from EVAP pressure switching solenoid. Blow air into inboard port (fuel tank pressure sensor port) of EVAP pressure switching solenoid. Air should pass through solenoid valve and exit out single port (EVAP canister port). Using scan tool, command EVAP pressure switching solenoid on. Blow air into inboard port (fuel tank pressure sensor port) of EVAP pressure switching solenoid. Air should pass through solenoid valve and exit out outboard port. If air flows as specified, go to step 42 . If air does not flow as specified, go to step 32 .
17. Check for an open or short in EVAP pressure switching solenoid control circuit between EVAP pressure switching solenoid and PCM. Repair as necessary. After repairs, go to step 43 . If circuit is okay, go to step 30 .
18. Repair open or short in EVAP pressure switching solenoid ignition positive voltage circuit between EVAP pressure switching solenoid and circuit opening relay located in junction block No. 1. After repairs, go to step 43 .
19. Disconnect vapor pressure supply hose to fuel tank pressure sensor. Using DVOM, measure voltage of fuel tank pressure sensor input circuit (Blue wire) at connector C221. See WIRING DIAGRAMS article. If voltage is 3-3.6 volts, go to next step. If voltage is not 3-3.6 volts, go to step 21 .
20. Repair cause of trapped vapor pressure to fuel tank pressure sensor. Check for pinched, crushed or restricted EVAP lines and hoses. Check for blocked or restricted EVAP components. Check for faulty EVAP solenoids or EVAP canister. Repair as necessary. After repairs, go to step 43 .
21. Turn ignition off. Disconnect fuel tank pressure sensor electrical connector. Turn ignition on, with engine off. Using DVOM, measure voltage of fuel tank pressure sensor reference voltage circuit at fuel tank pressure sensor connector (harness side). See WIRING DIAGRAMS article. If voltage is 5 volts, go to next step. If voltage is not 5 volts, go to step 23 .
22. Using DVOM, measure voltage of fuel tank pressure sensor input circuit at fuel tank pressure sensor connector (harness side). See WIRING DIAGRAMS article. If voltage is 4.9 volts, go to step 25 . If voltage is not 4.9 volts, go to step 24 .
23. Check for an open or short in fuel tank pressure sensor reference voltage circuit between fuel tank pressure sensor and PCM. Repair as necessary. After repairs, go to step 43 . If circuit is okay, go to step 41 .
24. Check for an open or short in fuel tank pressure sensor input circuit between fuel tank pressure sensor and PCM. Ensure fuel tank pressure sensor input circuit is not shorted to sensor ground circuit. Repair as necessary. After repairs, go to step 43 . If circuit is okay, go to step 41 .
25. Using test light connected to battery voltage, probe fuel tank pressure sensor connector ground circuit (harness side). See WIRING DIAGRAMS article. If test light illuminates, go to step 33 . If test light does not illuminate, go to next step.
26. Check for an open in fuel tank pressure sensor ground circuit between fuel tank pressure sensor and PCM. Repair as necessary. After repairs, go to step 43 . If circuit is okay, go to step 41 .
27. Remove ORVR vent line from EVAP canister and plug hose. Remove EVAP vapor line from EVAP canister and plug hose. Using EVAP pressure/purge diagnostic station, attempt to pressurize EVAP system to 30 in. H 2 O and hold. Using Ultrasonic Leak Detector (J-41416), check for any leaks in EVAP system. Lower fuel tank as necessary to inspect condition of fill limiter vent valve and rollover valve on top of tank. Also, check fuel sender assembly for a correct seal. If any EVAP or fuel supply system leaks are present, go to step 29 . If no leaks are present, go to next step.
28. Replace faulty/leaking EVAP canister. After repairs, go to step 43 .
29. Repair or replace leaking EVAP system or fuel tank component. After repairs, go to step 43 .
30. Using DVOM, measure resistance of EVAP pressure switching solenoid. If resistance is less than 27 ohms at 68°F (20°C), go to step 41 . If resistance is 27 ohms or greater at 68°F (20°C), go to next step.
31. Replace EVAP pressure switching solenoid and PCM. After repairs, go to step 43 .
32. Replace EVAP pressure switching solenoid. After repairs, go to step 43 .
33. Replace fuel tank pressure sensor. After repairs, go to step 43 .
34. Using DVOM, measure resistance of EVAP canister purge solenoid valve. If resistance is less than 27 ohms at 68°F (20°C), go to step 36 . If resistance is 27 ohms or greater at 68°F (20°C), go to next step.
35. Replace EVAP canister purge solenoid valve. After repairs, go to step 43 .
36. Replace EVAP canister purge solenoid valve and PCM. After repairs, go to step 43 .
37. Turn ignition on, with engine off. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Operate vehicle within freeze frame conditions. If DTC P0441 or P0446 resets, go to next step. If DTC P0441 or P0446 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S08233251722000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
38. Remove EVAP canister. Inspect EVAP canister for cracks or damage. Thoroughly inspect EVAP canister for damage. Replace canister as necessary. After repairs, go to step 43 . If canister is okay, go to next step.
39. Check for an open in EVAP canister purge solenoid valve control circuit between EVAP canister purge solenoid valve and PCM. Repair as necessary. After repairs, go to step 43 . If circuit is okay, go to step 41 .
40. Check for a short to ground in EVAP canister purge solenoid valve control circuit between EVAP canister purge solenoid valve and PCM. Repair as necessary. After repairs, go to step 43 . If circuit is okay, go to next step.
41. Replace PCM. Program PCM using required equipment. After replacing PCM, go to step 43 .
42. Repair restriction or blockage in fuel tank pressure sensor, hose from EVAP pressure switching solenoid to fuel tank pressure sensor, and hoses from EVAP canister to EVAP pressure switching solenoid. After repairs, go to next step.
43. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

DTC P0441 is most likely caused by a faulty EVAP canister purge solenoid valve. An intermittent DTC P0441 may be caused by a faulty EVAP canister that has released carbon particles and resulted in EVAP canister purge solenoid valve leakage. DTC P0446 is most likely caused by a faulty EVAP pressure switching solenoid. Check EVAP pressure switching solenoid for faulty connections and erratic operation. Check for problems in any of the following components or for any of the following conditions

1. Fuel tank pressure sensor.
2. EVAP canister purge solenoid valve.
3. EVAP pressure switching solenoid.
4. Faulty or leaking EVAP canister.
5. Damaged or leaky hoses, lines or fittings.
6. Faulty or leaking fill limiter vent valve.

Perform an inspection of all EVAP system components and vacuum hoses. See underhood vehicle emission control information label for component identification and vacuum hose routing.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Fuel tank pressure sensor responds to changes in fuel tank pressure or vacuum. Fuel tank pressure sensor signal voltage to PCM varies from greater than 4 volts with pressure in tank, to about .6 volt with high vacuum in tank (when vent solenoid is closed). DTC P0450 will set when

1. Vehicle speed is greater than 10 MPH for one minute.
2. Fuel level is 25-75 percent.
3. Fuel tank pressure sensor signal input voltage is less than .5 volt for at least .5 second.
4. Fuel tank pressure sensor signal input voltage is greater than 4.8 volts for at least .5 second.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Turn ignition off. Connect scan tool to DLC. Remove fuel filler cap. Turn ignition on, with engine off. Using scan tool, monitor fuel tank pressure sensor parameter. If fuel tank pressure sensor value is 0-.5 in. H 2 O, go to step 11 . If fuel tank pressure sensor value is not 0-.5 in. H 2 O, go to next step.
3. Remove rear seat cushion. Disconnect fuel tank pressure sensor harness electrical connector C310. Turn ignition on, with engine off. Connect a test light between battery voltage and fuel tank pressure sensor ground circuit terminal of connector C310 (body harness side). See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 8 .
4. Turn ignition on, with engine off. Using DVOM, measure voltage of fuel tank pressure sensor reference voltage circuit at connector C310 (harness side). See WIRING DIAGRAMS article. If voltage is 5 volts, go to next step. If voltage is not 5 volts, go to step 7 .
5. Remove fuel tank pressure sensor input wire from connector C310 (fuel tank harness side). Reconnect fuel tank pressure sensor harness electrical connector C310. Remove fuel filler cap. Turn ignition on, with engine off. Using DVOM connected to ground, measure voltage of fuel tank pressure sensor input circuit at connector C310. See WIRING DIAGRAMS article. If voltage is 2-2.6 volts go to next step. If voltage is not 2-2.6 volts, go to step 9 .
6. Check for an open or short in fuel tank pressure sensor input circuit between connector C310 and PCM. Repair as necessary. After repairs, go to step 20 . If circuit is okay, go to step 19 .
7. Check for an open or short in fuel tank pressure sensor reference voltage circuit between connector C310 and PCM. Repair as necessary. After repairs, go to step 20 . If circuit is okay, go to step 19 .
8. Check for an open in fuel tank pressure sensor ground circuit between connector C310 and PCM. Repair as necessary. After repairs, go to step 20 . If circuit is okay, go to step 19 .
9. Remove fuel tank. Remove fuel tank pressure sensor from fuel tank. Check for a clogged air vent hole and air pressure inlet passage in fuel tank pressure sensor. Repair as necessary. After repairs, go to step 20 . If air vent hole and air pressure inlet passage are clean, go to next step.
10. Check for an open in fuel tank pressure sensor reference voltage circuit and ground circuit between connector C311 and PCM. Check for an open or short in fuel tank pressure sensor input circuit between connector C311 and PCM. Repair as necessary. After repairs, go to step 20 . If circuits are okay, go to step 18 .
11. Remove rear seat cushion. Disconnect fuel tank EVAP solenoid harness electrical connector C311. Turn ignition on, with engine off. Connect a test light between battery voltage and EVAP tank pressure control solenoid vacuum valve control circuit of connector C311 (body harness side). See WIRING DIAGRAMS article. Using scan tool, command EVAP tank pressure control solenoid vacuum valve on and off while observing test light. If test light illuminates when solenoid is commanded on, go to step 13 . If test light does not illuminate when solenoid is commanded on, go to next step.
12. Check for an open in EVAP tank pressure control solenoid vacuum valve ignition positive voltage circuit. Check for an open or short in EVAP tank pressure control solenoid vacuum valve control circuit. Repair as necessary. After repairs, go to step 20 . If circuits are okay, go to step 19 .
13. Remove fuel tank. Check EVAP tank pressure control solenoid vacuum valve lines, hoses and connections for blockage or restriction. Repair as necessary. After repairs, go to step 20 . If lines, hoses and connections are okay, go to next step.
14. Remove EVAP tank pressure control solenoid vacuum valve. Blow air into side port of EVAP tank pressure control solenoid vacuum valve. If air flows through valve and out top port of EVAP tank pressure control solenoid vacuum valve, go to step 17 . If air does not flow through valve, go to next step.
15. Apply 12 volts to EVAP tank pressure control solenoid vacuum valve. Blow air into side port of EVAP tank pressure control solenoid vacuum valve. If air flows through valve and out top port of EVAP tank pressure control solenoid vacuum valve, go to next step. If air does not flow through valve, go to step 17 .
16. Repair open or short in EVAP tank pressure control solenoid vacuum valve wiring harness between valve and connector C311. After repairs, go to step 20 .
17. Replace EVAP tank pressure control solenoid vacuum valve. After repairs, go to step 20 .
18. Replace fuel tank pressure sensor. After repairs, go to step 20 .
19. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
20. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Check fuel tank pressure sensor for plugged air vent hole and clean as necessary. If DTCs P0108, P0113, P0118, P0123 and P0450 are set together, check for an open in sensor ground circuit. If DTCs P0107, P0122 and P0450 are set together, check for an open in 5-volt reference voltage circuit.

Road test vehicle. Using a scan tool, monitor fuel tank pressure sensor parameter. If -31.5 in. H 2 O is momentarily displayed, there may be an intermittent short to ground in fuel tank pressure sensor input circuit between fuel tank pressure sensor and PCM 22-pin connector. If 32-33 in. H 2 O is momentarily displayed, there may be an intermittent open in any fuel tank pressure sensor circuit.

Perform an inspection of all EVAP system components and vacuum hoses. See underhood vehicle emission control information label for component identification and vacuum hose routing.

Check for a poor PCM electrical connection. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

EVAP system includes fuel tank, fuel tank pressure sensor, EVAP pressure switching solenoid, fuel lines and hoses, vapor and purge lines, fuel cap, EVAP canister, and EVAP canister purge solenoid valve. PCM monitors positive and negative pressure in fuel tank using the fuel tank pressure sensor. PCM turns on the EVAP pressure switching solenoid to monitor positive and negative pressure in EVAP system under certain engine operating conditions. PCM detects any abnormal conditions by the fluctuation of this pressure. DTC P0450 will set when engine is running at normal operating temperature for at least 10 seconds, and fuel tank pressure sensor signal is greater than 0.6 in. Hg for 7 seconds, or fuel tank pressure sensor signal is less than -1.2 in. Hg for 7 seconds.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Remove fuel filler cap. Disconnect purge hose (canister side) at EVAP canister purge solenoid valve. Remove left kick panel. Turn ignition on, with engine off. Using DVOM connected to ground, backprobe fuel tank pressure sensor input circuit (Blue wire) at connector C221. See WIRING DIAGRAMS article. If voltage is 3-3.6 volts, go to next step. If voltage is not 3-3.6 volts, go to step 4 .
3. Turn ignition on, with engine off. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Operate vehicle within freeze frame conditions. If DTC P0450 resets, go to step 6 . If DTC P0450 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S20242280382000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
4. Disconnect vapor pressure supply hose to fuel tank pressure sensor. Using DVOM, measure voltage of fuel tank pressure sensor input circuit (Blue wire) at connector C221. See WIRING DIAGRAMS article. If voltage is 3-3.6 volts, go to next step. If voltage is not 3-3.6 volts, go to step 6 .
5. Repair cause of trapped vapor pressure to fuel tank pressure sensor. Check for pinched, crushed or restricted EVAP lines and hoses. Check for blocked or restricted EVAP components. Check for faulty EVAP solenoids or EVAP canister. Repair as necessary. After repairs, go to step 14 .
6. Turn ignition off. Disconnect fuel tank pressure sensor electrical connector. Turn ignition on, with engine off. Using DVOM, measure voltage of fuel tank pressure sensor reference voltage circuit at fuel tank pressure sensor connector (harness side). See WIRING DIAGRAMS article. If voltage is 5 volts, go to next step. If voltage is not 5 volts, go to step 8 .
7. Using DVOM, measure voltage of fuel tank pressure sensor input circuit at fuel tank pressure sensor connector (harness side). See WIRING DIAGRAMS article. If voltage is 4.9 volts, go to step 10 . If voltage is not 4.9 volts, go to step 9 .
8. Check for an open or short in fuel tank pressure sensor reference voltage circuit between fuel tank pressure sensor and PCM. Repair as necessary, After repairs, go to step 14 . If circuit is okay, go to step 13 .
9. Check for an open or short in fuel tank pressure sensor input circuit between fuel tank pressure sensor and PCM. Ensure fuel tank pressure sensor input circuit is not shorted to sensor ground circuit. Repair as necessary. After repairs, go to step 14 . If circuit is okay, go to step 13 .
10. Using test light connected to battery voltage, probe fuel tank pressure sensor connector ground circuit (harness side). See WIRING DIAGRAMS article. If test light illuminates, go to step 12 . If test light does not illuminate, go to next step.
11. Check for an open in fuel tank pressure sensor ground circuit between fuel tank pressure sensor and PCM. Repair as necessary, After repairs, go to step 14 . If circuit is okay, go to step 13 .
12. Replace fuel tank pressure sensor. After repairs, go to step 14 .
13. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
14. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

If DTCs P0105, P0110, P0115 and P0120 are also set, check for a problem in sensor ground circuit. If DTCs P0105 and P0120 are also set, check for a problem in 5-volt reference voltage circuit. Perform an inspection of all EVAP system components and vacuum hoses. See underhood vehicle emission control information label for component identification and vacuum hose routing.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Fuel tank pressure sensor responds to changes in fuel tank pressure or vacuum. Fuel tank pressure sensor signal voltage to PCM varies from greater than 4 volts with pressure in tank, to about .6 volt with high vacuum in tank (when vent solenoid is closed). DTC P0451 will set when

1. Fuel level is 25-75 percent.
2. Intake air temperature is 14-122°F (-10-50°C).
3. Engine coolant temperature is 158-230°F (70-110°C).
4. Barometric pressure is greater than 11 psi (75 kPa).
5. Engine running at idle for at least 2 minutes.
6. Fuel tank pressure is lower than specified value after completion of EVAP system leakage check.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Remove fuel filler cap. Turn ignition on, with engine off. Using scan tool, monitor fuel tank pressure sensor parameter. If fuel tank pressure sensor value is 0-.5 in. H 2 O, go to step 11 . If fuel tank pressure sensor value is not 0-.5 in. H 2 O, go to next step.
3. Remove rear seat cushion. Disconnect fuel tank pressure sensor harness electrical connector C310. Turn ignition on, with engine off. Connect a test light between battery voltage and fuel tank pressure sensor ground circuit terminal of connector C310 (body harness side). See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 8 .
4. Turn ignition on, with engine off. Using DVOM, measure voltage of fuel tank pressure sensor reference voltage circuit at connector C310 (harness side). See WIRING DIAGRAMS article. If voltage is 5 volts, go to next step. If voltage is not 5 volts, go to step 7 .
5. Remove fuel tank pressure sensor input wire from connector C310 (fuel tank harness side). Reconnect fuel tank pressure sensor harness electrical connector C310. Remove fuel filler cap. Turn ignition on, with engine off. Using DVOM connected to ground, measure voltage of fuel tank pressure sensor input circuit at connector C310. See WIRING DIAGRAMS article. If voltage is 2-2.6 volts go to next step. If voltage is not 2-2.6 volts, go to step 9 .
6. Check for an open in fuel tank pressure sensor input circuit between connector C310 and PCM. Repair as necessary. After repairs, go to step 21 . If circuit is okay, go to step 20 .
7. Check for an open or short in fuel tank pressure sensor reference voltage circuit between connector C310 and PCM. Repair as necessary. After repairs, go to step 21 . If circuit is okay, go to step 20 .
8. Check for open in fuel tank pressure sensor ground circuit between connector C310 and PCM. Repair as necessary. After repairs, go to step 21 . If circuit is okay, go to step 20 .
9. Remove fuel tank. Remove fuel tank pressure sensor from fuel tank. Check for a clogged air vent hole and air pressure inlet passage in fuel tank pressure sensor. Repair as necessary. After repairs, go to step 21 . If air vent hole and air pressure inlet passage are clean, go to next step.
10. Check for an open in fuel tank pressure sensor reference voltage circuit and ground circuit between connector C311 and PCM. Check for an open or short in fuel tank pressure sensor input circuit between connector C311 and PCM. Repair as necessary. After repairs, go to step 21 . If circuits are okay, go to step 18 .
11. Remove EVAP canister filter. Check filter for water or mud contamination. Check for blockage from dirt or debris. Check EVAP canister filter hoses for restriction or blockage. Repair as necessary. After repairs, go to step 21 . If circuits are okay, go to step 12 .
12. Remove rear seat cushion. Disconnect fuel tank EVAP solenoid harness electrical connector C311. Turn ignition on, with engine off. Connect a test light between battery voltage and EVAP canister vent solenoid control circuit of connector C311 (body harness side). See WIRING DIAGRAMS article. Using scan tool, command EVAP canister vent solenoid on and off while observing test light. If test light illuminates when solenoid is commanded on, go to step 14 . If test light does not illuminate when solenoid is commanded on, go to next step.
13. Check for an open in EVAP canister vent solenoid ignition positive voltage circuit. Check for an open or short in EVAP canister vent solenoid control circuit. Repair as necessary. After repairs, go to step 21 . If circuits are okay, go to step 20 .
14. Remove fuel tank. Check EVAP system lines, hoses and connections for blockage or restrictions. Repair as necessary. After repairs, go to step 21 . If lines, hoses and connections are okay, go to next step.
15. Remove EVAP canister vent solenoid. Using a hand-held vacuum pump, apply 15 in. Hg vacuum to canister side of EVAP canister vent solenoid. If solenoid holds vacuum, go to step 19 . If solenoid does not hold vacuum, go to next step.
16. Apply 12 volts to EVAP canister vent solenoid. Using a hand-held vacuum pump, apply 15 in. Hg vacuum to canister side of EVAP canister vent solenoid. If solenoid holds vacuum, go to next step . If solenoid does not hold vacuum, go to step 19 .
17. Check for an open or short in EVAP canister vent solenoid wiring harness between solenoid and connector C311. Repair as necessary. After repairs, go to step 21 If wiring harness is okay, go to «DIAGNOSTIC AIDS»(ref-189-S38929168022000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
18. Replace fuel tank pressure sensor. After repairs, go to step 21 .
19. Replace EVAP canister vent solenoid. After repairs, go to step 21 .
20. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
21. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Check for a shifted fuel tank pressure sensor. A shifted sensor could result in poor driveability complaints. Compare sensor voltage reading with a known good sensor. Check fuel tank pressure sensor for plugged air vent hole and clean as necessary. If DTCs P0108, P0113, P0118, P0123 and P0450 are set together, check for an open in sensor ground circuit. If DTCs P0107, P0122 and P0450 are set together, check for an open in 5-volt reference voltage circuit.

Perform an inspection of all EVAP system components and vacuum hoses. See underhood vehicle emission control information label for component identification and vacuum hose routing.

Check for a poor PCM electrical connection. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

PCM uses fuel level input from fuel tank level sensor to calculate expected vapor pressures within fuel system. Vapor pressure information is used to determine if EVAP system is operating properly. Fuel level information is also used by PCM to determine if fuel level is too high or too low to accurately detect EVAP system failures. DTC P0461 will set when fuel level change from maximum to minimum is less than one gallon even though volume of intake air is calculated to be greater than 660 kg. DTC P0463 will set when fuel tank level sensor voltage is greater than a specified value while engine is running for .5 second.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If DTC P0461 or P0463 resets, go to next step. If DTC P0461 or P0463 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S27215608412000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
3. Remove rear seat cushion. Disconnect fuel tank level sensor harness electrical connector C310. Turn ignition on, with engine off. Using DVOM, measure voltage of fuel tank level sensor input circuit at connector C310 (PCM side). See WIRING DIAGRAMS article. If voltage is 7-8 volts go to next step. If voltage is not 7-8 volts, go to step 8 .
4. Reconnect fuel tank level sensor harness electrical connector C310. Remove fuel tank. Disconnect fuel sender assembly electrical connector at fuel sender. Using DVOM connected to ground, measure voltage of fuel tank level sensor input circuit at connector C310 (PCM side). See WIRING DIAGRAMS article. If voltage is 7-8 volts, go to next step. If voltage is not 7-8 volts, go to step 9 .
5. Check for proper ground connection at fuel tank. Repair as necessary. After repairs, go to step 15 . If ground connection is okay, go to next step.
6. Remove fuel tank level sensor from fuel tank. Reconnect fuel sender assembly electrical connector. Using scan tool, monitor fuel tank level sensor parameter while moving sensor float from empty to full, and then back to empty several times. If fuel tank level sensor value increases to 90 percent, and then decreases steadily to zero percent as float is moved, go to «DIAGNOSTIC AIDS»(ref-189-S27215608412000030800000) . Check for presence of an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article. If fuel tank level sensor value is erratic or does not change, go to next step.
7. Fuel gauge responds slowly to changes in position of fuel tank level sensor float. Observe fuel gauge on instrument cluster while moving sensor float from empty to full, and then back to empty several times. If fuel gauge responds accordingly as float is moved, go to step 13 . If fuel gauge does not respond, go to step 10 .
8. Check for an open or short in fuel tank level sensor input circuit between connector C310, located under rear seat cushion, and PCM. Repair as necessary. After repairs, go to step 15 . If circuit is okay, go to step 11 .
9. Repair open or short in fuel tank level sensor input circuit between connector C310, located under rear seat cushion, and fuel tank level sensor. After repairs, go to step 15 .
10. Replace fuel tank level sensor. After repairs, go to step 15 .
11. Turn ignition off. Leave fuel tank level sensor harness electrical connector C310 disconnected. Disconnect PCM 22-pin electrical connector. Turn ignition on, with engine off. Using DVOM, measure voltage of fuel tank level sensor input circuit at PCM 22-pin connector (harness side). See WIRING DIAGRAMS article. If voltage is 7-8 volts, go to step 14 . If voltage is not 7-8 volts, go to next step.
12. Check for an open or short in fuel tank level sensor input circuit between instrument cluster fuel gauge and PCM. Repair as necessary. After repairs, go to step 15 . If circuit is okay, diagnose instrument cluster as necessary. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT.
13. Check for an open in fuel tank level sensor input circuit between instrument cluster fuel gauge and PCM. Repair as necessary. After repairs, go to step 15 . If circuit is okay, go to next step.
14. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
15. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

If DTC P0463 is also set, diagnose DTC before continuing. A stuck fuel tank level sensor may cause DTC P0461 to set. Check for a loose fuel tank baffle that may interfere with movement of fuel tank level sensor float. Check for a corroded or loose fuel tank level sensor chassis ground. An open in fuel tank level sensor circuit will indicate an empty fuel tank (zero percent fuel level). A short to ground in fuel tank level sensor circuit will indicate a full fuel tank (100 percent fuel level).

Check for a poor PCM electrical connection. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Cooling fan motor is controlled by PCM through cooling fan relay. PCM uses Engine Coolant Temperature (ECT) sensor output to calculate when to operate engine cooling fan motor. When engine temperature is greater than 208°F (98°C), PCM will provide a ground path for cooling fan relay and activate cooling fan motor. When engine temperature drops to less than 199°F (93°C), PCM will remove ground path and deactivate cooling fan motor. DTC P0480 will set when low voltage is indicated at cooling fan relay control terminal for 5 seconds with engine coolant temperature less than 199°F (93°C).

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. Connect scan tool to DLC. Using scan tool, monitor ECT sensor parameter. If cooling fan is off when ECT is less than 194°F (90°C), go to next step. If cooling fan turns on, go to step 4 .
3. Turn ignition on, with engine off. Connect scan tool to DLC. Using scan tool, clear DTC information. Operate cooling fan with scan tool. If cooling fan turns on and off when commanded by scan tool, go to «DIAGNOSTIC AIDS»(ref-189-S17612020532000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article. If cooling fan does not operate when commanded by scan tool, go to next step.
4. Ensure ECT is less than 194°F (90°C). Disconnect cooling fan relay located in relay box, in left side of engine compartment. If cooling fan turns off, go to next step. If cooling fan does not turn off, go to step 6 .
5. Using test light connected to battery voltage, probe cooling fan relay connector cavity cooling fan relay control circuit. See WIRING DIAGRAMS article. If test light illuminates, go to step 7 . If test light does not illuminate, go to step 17 .
6. Repair a short to voltage in power feed circuit between cooling fan relay and cooling fan motor. After repairs, go to step 20 .
7. Check for a short to ground in cooling fan relay control circuit between cooling fan relay and PCM. Repair as necessary. After repairs, go to step 20 . If circuit is okay, go to step 18 .
8. Turn ignition on, with engine off. Remove cooling fan relay. Using test light connected to ground, probe cooling fan relay connector cavity ignition feed circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 15 .
9. Using test light connected to ground, probe cooling fan relay connector cavity battery feed circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 16 .
10. Connect a fused jumper wire between cooling fan relay connector cavities battery feed circuit and power feed circuit. See WIRING DIAGRAMS article. If cooling fan motor operates, go to next step. If cooling fan motor does not operate, go to step 13 .
11. Using test light connected to battery voltage, probe cooling fan relay connector cavity cooling fan relay control circuit. See WIRING DIAGRAMS article. Using scan tool, command cooling fan on. If test light illuminates, go to step 17 . If test light does not illuminate, go to next step.
12. Check for an open in cooling fan relay control circuit between cooling fan relay and PCM. Repair as necessary. After repairs, go to step 20 . If circuit is okay, go to step 18 .
13. Check for an open in power feed circuit between cooling fan relay and cooling fan motor. Repair as necessary. After repairs, go to step 20 . If circuit is okay, go to next step.
14. Check for an open or poor connection in ground circuit between cooling fan motor and ground connection. Repair as necessary. After repairs, go to step 20 . If circuit is okay, go to step 19 .
15. Repair open in ignition feed circuit between cooling fan relay and junction block located behind left side of instrument panel. After repairs, go to step 20 .
16. Repair open in battery feed circuit between cooling fan relay and fuse box located in left side of engine compartment. After repairs, go to step 20 .
17. Replace cooling fan relay. After repairs, go to step 20 .
18. Replace PCM. Program PCM using required equipment. After replacing PCM, go to step 20 .
19. Replace cooling fan motor. After repairs, go to next step.
20. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Determine if overheating complaint is from a boil over, or warning indicator light or temperature gauge. Check warning indicator light or temperature gauge circuits if overheating was indicated without a boilover. If boilover occurred and warning indicator or temperature gauge indicated overheating, but cooling fan did not operate, check for a shifted ECT sensor. If engine overheats and cooling fan operates, ensure engine system condition is okay. Check for a blown fuse(s) which can also cause cooling fan motor malfunction.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Vehicle Speed Sensor (VSS) is located behind instrument cluster. PCM supplies a 5-volt signal to VSS. While vehicle is moving, a reed switch inside VSS will open and close, 4 times per revolution, toggling 5-volt signal high and low. PCM converts this toggled high/low voltage into a vehicle speed that is displayed as MPH (KM/H). DTC P0500 will set when vehicle speed sensor signal in not present during fuel cut-off mode for greater than 4 seconds.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer. PCM will enter Fail-Safe Function and stop Idle Speed Control (ISC) operation.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Raise vehicle and support drive axles. Start engine and allow to idle in gear. If scan tool displays a vehicle speed greater than zero MPH, go to next step. If scan tool displays a vehicle speed of zero MPH, go to step 4 .
3. Lower vehicle. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If DTC P0500 resets, go to next step. If DTC P0500 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S23107145512000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
4. Turn ignition off. Disconnect instrument cluster 13-pin connector located behind upper left corner of instrument cluster. Using DVOM, measure voltage between ground and instrument cluster 13-pin connector (harness side) VSS input circuit. See WIRING DIAGRAMS article. Turn ignition on, with engine off. If voltage is 4-6 volts, go to next step. If voltage is not 4-6 volts, go to step 7 .
5. Using test light connected to battery voltage, probe instrument cluster 13-pin connector VSS ground circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 8 .
6. Check instrument cluster printed circuit for cracks or poor connections. Repair as necessary. After repairs, go to step 11 . If printed circuit is okay, go to step 9 .
7. Check for open or short in VSS input circuit between VSS and PCM. Repair as necessary. After repairs, go to step 11 . If circuit is okay, go to step 10 .
8. Repair open or poor connection in VSS ground circuit. After repairs, go to step 11 .
9. Replace speedometer assembly. After repairs, go to step 11 .
10. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
11. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

If speedometer cable is binding, a false DTC P0500 can be set. Ensure speedometer cable is free from restrictions and has a secure connection to instrument cluster. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Vehicle speed information is supplied to PCM by Vehicle Speed Sensor (VSS). VSS is a magnet generator mounted in transaxle that produces a pulsating AC voltage. AC voltage level and number of pulses increase with vehicle speed. DTC P0500 will set when vehicle speed sensor signal is not present during fuel cut-off mode for greater than 4 seconds.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of diagnostic failure and store information in freeze frame buffer. PCM will enter Fail-Safe Function and stop idle speed feedback control.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Raise vehicle and support drive axles. Start engine and allow to idle in gear. If scan tool displays a vehicle speed greater than zero MPH, go to next step. If scan tool displays a vehicle speed of zero MPH, go to step 4 .
3. Lower vehicle. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If DTC P0500 resets, go to next step. If DTC P0500 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S06445677132000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
4. Turn ignition off. Disconnect VSS electrical connector. Using DVOM, measure resistance of VSS. If resistance is 100-300 ohms at 68°F (20°C), go to next step. If resistance is not 100-300 ohms at 68°F (20°C), go to step 6 .
5. Check for an open or short to ground/voltage in VSS high and low circuits between VSS and PCM. See WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step 9 . If circuits are okay, go to step 7 .
6. Replace VSS. After repairs, go to step 9 .
7. Remove VSS. Check counter shaft gear for damaged or missing teeth, or foreign material. Repair as necessary. After repairs go to step 9 . If VSS is okay, go to next step.
8. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
9. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Vehicle Speed Sensor (VSS) is mounted on transaxle. As transaxle rotates VSS, speedometer is provided with a vehicle speed input (voltage pulses). This signal drives speedometer. Speedometer converts vehicle speed input into a more precise waveform, providing PCM and cruise control module with a vehicle speed input. PCM converts this input (ground pulses) into vehicle speed. DTC P0500 will set when vehicle speed sensor signal is not present at PCM with engine speed 2000-5000 RPM (M/T), or when vehicle speed sensor signal is not present at PCM with engine speed equal to or greater than 2350 RPM, TP angle is equal to or greater than 13 degrees, Park/Neutral Position (PNP) switch is off, and engine parameters indicate vehicle is being driven (A/T).

When DTC sets, on M/T and 3-speed A/T, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. On 4-speed A/T, MIL will illuminate after first ignition cycle in which diagnostic runs with active fault. On all models, PCM will record operating conditions at time of diagnostic failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Raise and support drive wheels under lower control arms so that drive axles are in a horizontal (straight) position. Start engine and allow to idle in gear with drive wheels rotating. If scan tool displays a vehicle speed greater than zero MPH, go to next step. If scan tool displays a vehicle speed of zero MPH, go to step 4 .
3. Lower vehicle. Turn ignition on, with engine off. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Operate vehicle within freeze frame conditions. If DTC P0500 resets, go to next step. If DTC P0500 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S09348339422000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
4. If speedometer operates, go to step 10 . If speedometer does not operate, go to next step.
5. If all other instrument cluster assembly functions operate normally, go to next step. If any other instrument cluster assembly functions does not operate normally, diagnose instrument cluster as necessary. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT.
6. Turn ignition off. Disconnect VSS electrical connector. Turn ignition on, with engine off. Using test light connected to ground, probe VSS connector VSS power feed circuit (harness side). See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 12 .
7. Using test light connected to battery voltage, probe VSS connector VSS ground circuit (harness side). See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 13 .
8. Using test light connected to battery voltage, probe VSS connector VSS input circuit. See WIRING DIAGRAMS article. If test light illuminates, go to step 14 . If test light does not illuminate, go to next step.
9. Reconnect VSS electrical connector. Disconnect instrument cluster 13-pin Blue connector. Set DVOM to measure DC frequency. Using DVOM, measure frequency of VSS input circuit at instrument cluster 13-pin Blue connector. See WIRING DIAGRAMS article. Start engine and allow to idle in gear with drive wheels rotating. If DVOM indicates a frequency, go to step 18 . If DVOM does not indicate a frequency, go to step 15 .
10. Turn ignition off. Disconnect PCM connector C3. Turn ignition on, with engine off. Using DVOM connected to ground, measure voltage of VSS input circuit (harness side) at PCM connector C3. See WIRING DIAGRAMS article. If voltage is 9-12 volts, go to next step. If voltage is not 9-12 volts, go to step 16 .
11. Set DVOM to measure DC frequency. Using DVOM, measure frequency of VSS input circuit at PCM connector C3. See WIRING DIAGRAMS article. Start engine and allow to idle in gear with drive wheels rotating. If DVOM indicates a frequency, go to step 20 . If DVOM does not indicate a frequency, go to step 17 .
12. Repair cause of no power to VSS connector. Repair as necessary. After repairs, go to step 21 .
13. Repair cause of no ground to VSS connector. Repair as necessary. After repairs, go to step 21 .
14. Check for a short to ground in VSS input circuit between instrument cluster and VSS. Repair as necessary. After repairs, go to step 21 . If circuit is okay, go to step 18 .
15. Check for an open in VSS input circuit between instrument cluster and VSS. Repair as necessary. After repairs, go to step 21 . If circuit is okay, go to step 19 .
16. Check for an open or short to ground in VSS input circuit between PCM and junction block No. 3. Ensure cruise control module is not internally shorted (if equipped). Repair as necessary. After repairs, go to step 21 . If circuit is okay, go to step 18 .
17. Check for a short to voltage in VSS input circuit between PCM and junction block No. 3. Repair as necessary. After repairs, go to step 21 . If circuit is okay, go to step 18 .
18. Replace speedometer assembly. After repairs, go to step 21 .
19. Replace VSS. After repairs, go to step 21 .
20. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
21. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Scan tool should indicate a vehicle speed whenever drive wheels are turning greater than 3 MPH. A false DTC P0500 can be set if engine is brake-torqued in gear. Disregard DTC if set when drive wheels are not turning. An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Idle Speed Control (ISC) motor opens and closes throttle valve according to signals from PCM. When a condition occurs requiring a higher idle speed, PCM will send a signal to ISC motor which will extend plunger of ISC motor, which opens throttle plates to increase idle speed. PCM will reverse polarity to ISC motor causing throttle plates to close, thus decreasing idle speed when higher idle speed is no longer necessary. DTC P0505 will set when

1. Closed Throttle Position (CTP) switch is on.
2. Battery voltage is greater than 12 volts.
3. Engine coolant temperature is greater than 84°F (30°C).
4. Throttle valve feed back check indicates ISC motor movement is less than .244 inches. This check will run 10 continuous times per drive cycle.
5. ISC motor voltage check indicates no operation signal from PCM. This check will run 2 continuous times per drive cycle.

When DTC sets, MIL will illuminate. PCM will record operating conditions at time of diagnostic failure and store information in freeze frame buffer. PCM will enter Fail-Safe Function and stop Idle Speed Control (ISC) operation.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Start engine and allow it to reach normal operating temperature. Using scan tool, clear DTC. Using scan tool, monitor RPM output control parameter. Observe ISC plunger while attempting to raise and lower idle speed with scan tool. If ISC plunger extends during increase in RPM and retracts during decrease in RPM, go to next step. If ISC plunger does not operate as specified, go to step 4 .
3. Turn ignition on, with engine off. Review freeze frame data. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If DTC P0505 resets, go to next step. If DTC P0505 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S05824969472000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
4. Turn ignition off. Disconnect ISC motor relay located in relay box, in left side of engine compartment. Turn ignition on, with engine off. Using test light connected to ground, probe ISC motor relay connector cavity ignition feed circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 11 .
5. Using DVOM, measure resistance between ISC motor relay terminals No. 3 (Gray wire) and No. 4 (White/Blue wire). See WIRING DIAGRAMS article. If resistance is infinite, go to next step. If resistance is not infinite, go to step 12 .
6. Using DVOM, measure resistance between ISC terminals No. 1 (White/Blue wire) and No. 2 (Gray/Black wire). See WIRING DIAGRAMS article. If resistance is 75-95 ohms, go to next step. If resistance is not 75-95 ohms, go to step 12 .
7. Turn ignition off. Disconnect PCM electrical connectors. Connect a fused jumper wire between battery voltage and ISC motor relay connector cavity ISC motor relay control circuit. See WIRING DIAGRAMS article. Using DVOM, measure voltage at PCM 26-pin connector (harness side) ISC motor relay control circuit. If battery voltage is present, go to next step. If battery voltage is not present, go to step 13 .
8. Turn ignition off. Connect ISC motor relay. Disconnect PCM 26-pin connector. Back out PCM 26-pin connector terminals No. 11 (Gray/Yellow wire), No. 16 (Gray/Black wire), and No. 24 (Gray/Red wire). Reconnect PCM connector with specified wire terminals removed. Connect a fused jumper wire between PCM 26-pin connector terminal No. 16 (Gray/Black wire) and ground. Turn ignition on, with engine off. Ensure ISC motor actuator plunger contacts throttle lever. Connect 4, NEW 1.5 volt batteries in series. Connect PCM 26-pin connector terminal No. 24 (Gray/Red wire) to negative side of batteries. Momentarily connect PCM 26-pin connector terminal No. 11 (Gray/Yellow wire) to positive side of batteries. If ISC motor plunger extends out, go to next step. If ISC motor plunger does not extend out, go to step 14 .
9. Turn ignition on, with engine off. Ensure ISC motor actuator plunger contacts throttle lever. Connect PCM 26-pin connector terminal No. 11 (Gray/Yellow wire) to negative side of batteries. Momentarily connect PCM 26-pin connector terminal No. 24 (Gray/Red wire) to positive side of batteries. If ISC motor plunger retracts, go to next step. If ISC motor plunger does not retract, go to step 14 .
10. Turn ignition off. Disconnect 1.5 volt batteries and reinstall PCM 26-pin connector terminals No. 11 (Gray/Yellow wire), No. 16 (Gray/Black wire), and No. 24 (Gray/Red wire). Turn ignition on, with engine off. Disconnect ISC motor electrical connector. Using test light connected to battery voltage, probe ISC motor connector ISC motor ground circuit. See WIRING DIAGRAMS article. If test light illuminates, go to step 16 . If test light does not illuminate, go to step 15 .
11. Repair open in ignition feed circuit between ISC motor relay and main relay located in relay box, in left side of engine compartment. After repairs, go to step 18 .
12. Replace ISC motor relay. After repairs, go to step 18 .
13. Repair open or short in ISC motor relay control circuit between ISC motor relay and PCM. After repairs, go to step 18 .
14. Check for an open or short in ISC motor control circuits (Gray/Yellow wire, Gray/Red wire and Gray wire). Repair as necessary. After repairs, go to step 18 . If circuits are okay, go to step 17 .
15. Repair open in ISC motor ground circuit. After repairs, go to step 18 .
16. Replace PCM. Program PCM using required equipment. After replacing PCM, go to step 18 .
17. Replace ISC motor. After repairs, go to next step.
18. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

If DTC P0510 is also set, diagnose DTC before continuing. Ensure throttle plate is not stuck or binding, and movement is smooth and even. Check for a short to ground in Closed Throttle Position (CTP) switch circuit. See WIRING DIAGRAMS article. Check throttle cable adjustment. Ensure correct PCV valve is installed and no vacuum leaks are present.

Check for a poor PCM electrical connection. Check for damaged wiring harness. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

PCM control Idle Air Control (IAC) valve to regulate airflow through idle air by-pass passage. Idle speed is determined by the amount of air flowing through idle air by-pass passage. IAC valve is regulated according to engine load. A malfunctioning IAC valve could cause a stalling condition. DTC P0505 will set when PCM does not receive a closed signal from IAC valve after engine is started. When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Start engine and allow it to reach normal operating temperature. Turn off all electrical accessories. Using scan tool, monitor IAC duty cycle parameter. If scan tool indicates IAC duty cycle is 8-25 percent, go to «DIAGNOSTIC AIDS»(ref-189-S39000648312000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article. If scan tool does not indicate IAC duty cycle is 8-25 percent, go to next step.
3. Check for vacuum leaks, incorrectly routed vacuum lines and hoses, split or damaged vacuum lines and hoses, blocked inlet air ducts and passages, and plugged air filter element. Repair as necessary. After repairs, go to step 14 . If no problem is found, go to next step.
4. Disconnect IAC valve electrical connector. Turn ignition on, with engine off. Using test light connected to ground, probe IAC valve connector (harness side) IAC valve battery voltage circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 6 .
5. Using DVOM, probe IAC valve connector (harness side) IAC valve battery voltage circuit. See WIRING DIAGRAMS article. If battery voltage is present, go to step 7 . If battery voltage is not present, go to next step.
6. Repair open or short in IAC valve battery voltage circuit between IAC valve and main relay located in relay box, in left side of engine compartment. After repairs, go to step 14 .
7. Using test light connected to battery voltage, probe IAC valve connector (harness side) IAC valve ground circuit. See WIRING DIAGRAMS article. If test light illuminates, go to step 9 . If test light does not illuminate, go to next step.
8. Repair open in IAC valve ground circuit between IAC valve and ground connection. After repairs, go to step 14 .
9. Turn ignition off. Connect IAC valve electrical connector to IAC valve. Disconnect PCM 22-pin connector. Back out PCM 22-pin connector IAC valve control circuit terminal. Reconnect PCM connector with IAC valve control circuit wire terminal removed. Turn ignition on, with engine off. Using DVOM, probe PCM 22-pin connector IAC valve control circuit. See WIRING DIAGRAMS article. If battery voltage is present, go to next step. If battery voltage is not present, go to step 11 .
10. Start engine. Using scan tool, monitor engine speed parameter. Using test light connected to ground, momentarily probe PCM 22-pin connector IAC valve control circuit. See WIRING DIAGRAMS article. If engine speed increases when test light contacts IAC valve control circuit, go to step 13 . If engine speed does not increase when test light contacts IAC valve control circuit, go to step 12 .
11. Check for an open or short in IAC valve control circuit between IAC valve and PCM. Repair as necessary. After repairs, go to step 14 . If circuit is okay, go to next step.
12. Replace IAC valve. After repairs, go to step 14 .
13. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
14. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Ensure engine idle speed is correct. Check for a collapsed air intake duct, restricted air filter element, or foreign objects blocking air intake system, IAC passage or throttle bore. Check throttle plate for smooth and even movement. Check IAC passage, throttle bore, and throttle plate for excessive deposits. Check throttle cable for correct adjustment and free-play. Ensure correct PCV valve is installed, brake booster hose is not disconnected, and no vacuum leaks are present.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

PCM controls engine idle with Idle Air Control (IAC) valve. To increase idle speed, PCM pulse width modulates the OPEN solenoid inside IAC valve. A cylinder turns within IAC valve and allows air to by-pass throttle plate. PCM regulates (fast) idle speed using the IAC valve by increasing the opening of the air bypass port. PCM regulates (slow) idle speed using the IAC valve by decreasing the opening of the air bypass port. DTC P0505 will set when actual idle speed varies greatly from desired idle speed. When DTC sets, MIL will illuminate after first ignition cycle in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Start engine and allow it to reach normal operating temperature (closed loop) Using scan tool, store freeze frame and DTC information. Turn ignition off and wait 30 seconds. Turn ignition on, with engine off. Using scan tool, clear DTC information. Start and idle engine. Wait 60 seconds, and then check for DTCs. If DTC P0505 resets, go to step 4 . If DTC P0505 does not reset, go to next step.
3. If idle quality is poor, diagnosis by symptom. See appropriate TROUBLE SHOOTING - NO CODES article. If idle quality is okay, go to «DIAGNOSTIC AIDS»(ref-189-S13899228012000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
4. Turn ignition off. Disconnect IAC valve electrical connector. Turn ignition on, with engine off. Using test light connected to ground, probe IAC valve connector (harness side) IAC valve battery voltage circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 8 .
5. Using test light connected to battery voltage, probe IAC valve connector (harness side) IAC valve ground circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 9 .
6. Turn ignition off. Connect a jumper wire from IAC valve open control circuit terminal of IAC valve connector to IAC valve open control circuit terminal of IAC valve. See WIRING DIAGRAMS article. Connect a second jumper wire from ground circuit terminal of IAC valve connector to ground circuit terminal of IAC valve. Connect a fused jumper wire to battery voltage circuit of IAC valve and insulate jumper from electrical ground contact. Start engine and let idle. With engine idling, repeatedly touch IAC valve battery voltage circuit jumper to battery ground with a rapid on/off motion. If engine speed increases as IAC valve battery voltage circuit is rapidly grounded on and off, go to next step. If engine speed does not increase as specified, go to step 10 .
7. Turn ignition off. Remove all jumper wires. Disconnect PCM 26-pin connector. Check for a grounded, open or short to voltage in IAC valve open control circuit between IAC valve and PCM. Repair as necessary. After repairs, go to step 12 . If circuit is okay, go to step 11 .
8. Locate cause of no power to IAC valve connector. Repair as necessary. After repairs, go to step 12 .
9. Repair open in IAC valve ground circuit between IAC valve and ground connection. Repair as necessary. After repairs, go to step 12 .
10. IAC valve seals the coolant passage of throttle body. Replace IAC valve. Repair as necessary. After repairs, go to step 12 .
11. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
12. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Check air intake system for blockage. Check IAC passage or throttle bore for blockage, excessive deposits in IAC passage and IAC pintle. Check for excessive deposits in throttle bore and throttle blade. Ensure vacuum hoses are routed correctly and no vacuum leaks are present.

Ensure engine is idling at normal operating temperature and all electrical accessories are off. Using scan tool, ensure IAC duty cycle is 27-43 percent and that there is no electric load and A/C is commanded off.

An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Idle Speed Control (ISC) motor opens and closes throttle valve according to signals from PCM. When a condition occurs requiring a higher idle speed, PCM will send a signal to ISC motor which will extend plunger of ISC motor, which opens throttle plates to increase idle speed. PCM will reverse polarity to ISC motor causing throttle plates to close, thus decreasing idle speed when higher idle speed is no longer necessary. DTC P0506 will set when

1. Closed Throttle Position (CTP) switch is on.
2. Battery voltage is greater than 12 volts.
3. Engine coolant temperature is greater than 176°F (80°C).
4. Intake air temperature is 14-122°F (-10-50°C).
5. Fuel level is greater than 25 percent.
6. Barometric pressure is greater than 11 psi (75 kPa).
7. Engine running for 5 minutes or more.
8. Engine idle speed is less than target idle speed by 100 RPM or more.

MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Check for DTCs other than DTC P0506, P0507, P0171, P0172, P0300, P0301, P0302, or P0303. If any other DTCs not listed are set, diagnose DTC(s). If no other DTCs than those listed are set, go to next step.
3. Start engine and allow it to reach normal operating temperature. Turn off all electrical accessories. Using scan tool, monitor RPM parameter. If engine RPM parameter is less than 800-900 RPM by 100 RPM or more, go to step 5 . If engine RPM parameter is not as specified, go to next step.
4. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If DTC P0506 resets, go to next step. If DTC P0506 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S39256185382000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
5. Check for cracked, split or misrouted vacuum hoses. Check for restrictions in air intake system. Ensure ignition timing is adjusted properly. Repair as necessary. After repairs, go to step 19 . If no problem is found, go to next step.
6. Turn ignition off. Disconnect ISC motor relay located in relay box, in left side of engine compartment. Turn ignition on, with engine off. Using test light connected to ground, probe ISC motor relay connector cavity ignition feed circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 12 .
7. Using DVOM, measure resistance between ISC motor relay terminals No. 3 (Gray wire) and No. 4 (White/Blue wire). See WIRING DIAGRAMS article. If resistance is infinite, go to next step. If resistance is not infinite, go to step 13 .
8. Using DVOM, measure resistance between ISC terminals No. 1 (White/Blue wire) and No. 2 (Gray/Black wire). See WIRING DIAGRAMS article. If resistance is 75-95 ohms, go to next step. If resistance is not 75-95 ohms, go to step 13 .
9. Turn ignition off. Disconnect PCM electrical connectors. Connect a fused jumper wire between battery voltage and ISC motor relay connector cavity ISC motor relay control circuit. See WIRING DIAGRAMS article. Using DVOM, measure voltage at PCM 26-pin connector (harness side) ISC motor relay control circuit. If battery voltage is present, go to next step. If battery voltage is not present, go to step 14 .
10. Turn ignition off. Connect ISC motor relay. Disconnect PCM 26-pin connector. Back out PCM 26-pin connector terminals No. 11 (Gray/Yellow wire), No. 16 (Gray/Black wire), and No. 24 (Gray/Red wire). Reconnect PCM connector with specified wire terminals removed. Connect a fused jumper wire between PCM 26-pin connector terminal No. 16 (Gray/Black wire) and ground. Turn ignition on, with engine off. Ensure ISC motor actuator plunger contacts throttle lever. Connect 4, NEW 1.5 volt batteries in series. Connect PCM 26-pin connector terminal No. 24 (Gray/Red wire) to negative side of batteries. Momentarily connect PCM 26-pin connector terminal No. 11 (Gray/Yellow wire) to positive side of batteries. If ISC motor plunger extends out, go to next step. If ISC motor plunger does not extend out, go to step 15 .
11. Turn ignition off. Disconnect 1.5 volt batteries and reinstall PCM 26-pin connector terminals No. 11 (Gray/Yellow wire), No. 16 (Gray/Black wire), and No. 24 (Gray/Red wire). Turn ignition on, with engine off. Using test light connected to battery voltage, probe ISC motor connector ISC motor ground circuit. See WIRING DIAGRAMS article. If test light illuminates, go to step 17 . If test light does not illuminate, go to step 16 .
12. Repair open in ignition feed circuit between ISC motor relay and main relay located in relay box, in left side of engine compartment. After repairs, go to step 19 .
13. Replace ISC motor relay. After repairs, go to step 19 .
14. Repair open or short in ISC motor relay control circuit between ISC motor relay and PCM. After repairs, go to step 19 .
15. Check for an open or short in ISC motor control circuits (Gray/Yellow wire, Gray/Red wire and Gray wire). Repair as necessary. After repairs, go to step 19 . If circuits are okay, go to step 18 .
16. Repair open in ISC motor ground circuit. After repairs, go to step 19 .
17. Replace PCM. Program PCM using required equipment. After replacing PCM, go to step 19 .
18. Replace ISC motor. After repairs, go to next step.
19. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

If DTC P0510 is also set, diagnose DTC before continuing. Ensure throttle plate is not stuck or binding, and movement is smooth and even. Ensure correct PCV valve is installed and no vacuum leaks are present. Check Throttle Position (TP) sensor for accuracy. Using scan tool, ensure ISC duty cycle parameter is 20-40 percent at normal engine operating temperature.

Check for a poor PCM electrical connection. Check for damaged wiring harness. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

PCM control Idle Air Control (IAC) valve to regulate air flow through idle air by-pass passage. Idle speed is determined by the amount of air flowing through idle air by-pass passage. IAC valve is regulated according to engine load. A malfunctioning IAC valve could cause a stalling condition. DTC P0506 will set when TP sensor indicates a closed throttle position with engine coolant temperature greater than 176°F (80°C) and engine idle speed is 100 RPM or less than desired idle. When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Start engine and allow it to reach normal operating temperature. Turn off all electrical accessories. Using scan tool, monitor IAC duty cycle parameter. If scan tool indicates IAC duty cycle is 8-25 percent, go to «DIAGNOSTIC AIDS»(ref-189-S28250553682000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article. If scan tool does not indicate IAC duty cycle is 8-25 percent, go to next step.
3. Check for vacuum leaks, incorrectly routed vacuum lines and hoses, split or damaged vacuum lines and hoses, blocked inlet air ducts and passages, and plugged air filter element. Repair as necessary. After repairs, go to step 14 . If no problem is found, go to next step.
4. Disconnect IAC valve electrical connector. Turn ignition on, with engine off. Using test light connected to ground, probe IAC valve connector (harness side) IAC valve battery voltage circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 6 .
5. Using DVOM, probe IAC valve connector (harness side) IAC valve battery voltage circuit. See WIRING DIAGRAMS article. If battery voltage is present, go to step 7 . If battery voltage is not present, go to next step.
6. Repair open or short in IAC valve battery voltage circuit between IAC valve and main relay located in relay box, in left side of engine compartment. After repairs, go to step 14 .
7. Using test light connected to battery voltage, probe IAC valve connector (harness side) IAC valve ground circuit. See WIRING DIAGRAMS article. If test light illuminates, go to step 9 . If test light does not illuminate, go to next step.
8. Repair open in IAC valve ground circuit between IAC valve and ground connection. After repairs, go to step 14 .
9. Turn ignition off. Disconnect IAC valve electrical connector. Disconnect PCM 22-pin connector. Turn ignition on, with engine off. Using DVOM, probe PCM 22-pin connector (harness side) IAC valve control circuit. See WIRING DIAGRAMS article. If voltage is present, go to step 11 . If voltage is not present, go to next step.
10. Start engine. Using scan tool, monitor engine speed parameter. Using test light connected to ground, momentarily probe PCM 22-pin connector IAC valve control circuit. See WIRING DIAGRAMS article. If engine speed fluctuates when test light contacts IAC valve control circuit, go to step 13 . If engine speed does not fluctuate when test light contacts IAC valve control circuit, go to step 12 .
11. Check for a short to voltage in IAC valve control circuit between IAC valve and PCM. Repair as necessary. After repairs, go to step 14 . If circuit is okay, go to next step.
12. Replace IAC valve. After repairs, go to step 14 .
13. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
14. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Ensure engine idle speed is correct. Check for a collapsed air intake duct, restricted air filter element, or foreign objects blocking air intake system, IAC passage or throttle bore. Check throttle plate for smooth and even movement. Check IAC passage, throttle bore, and throttle plate for excessive deposits. Ensure correct PCV valve is installed, brake booster hose is not disconnected, and no vacuum leaks are present.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Idle Speed Control (ISC) motor opens and closes throttle valve according to signals from PCM. When a condition occurs requiring a higher idle speed, PCM will send a signal to ISC motor which will extend plunger of ISC motor, which opens throttle plates to increase idle speed. PCM will reverse polarity to ISC motor causing throttle plates to close, thus decreasing idle speed when higher idle speed is no longer necessary. DTC P0507 will set when

1. Closed Throttle Position (CTP) switch is on.
2. Battery voltage is greater than 12 volts.
3. Engine coolant temperature is greater than 176°F (80°C).
4. Intake air temperature is 14-122°F (-10-50°C).
5. Fuel level is greater than 25 percent.
6. Barometric pressure is greater than 11 psi (75 kPa).
7. Engine running for 5 minutes or more.
8. Engine idle speed is greater than target idle speed by 200 RPM or more.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Check for DTCs other than DTC P0506, P0507, P0171, P0172, P0300, P0301, P0302, or P0303. If any other DTCs not listed are set, diagnose DTC(s). If no other DTCs than those listed are set, go to next step.
3. Start engine and allow it to reach normal operating temperature. Turn off all electrical accessories. Using scan tool, monitor RPM parameter. If engine RPM parameter is less than 800-900 RPM by 200 RPM or more, go to step 5 . If engine RPM parameter is not as specified, go to next step.
4. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If DTC P0507 resets, go to next step. If DTC P0507 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S05569937382000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
5. Check for cracked, split or misrouted vacuum hoses. Check for restrictions in air intake system. Ensure ignition timing is adjusted properly. Repair as necessary. After repairs, go to step 19 . If no problem is found, go to next step.
6. Turn ignition off. Disconnect ISC motor relay located in relay box, in left side of engine compartment. Turn ignition on, with engine off. Using test light connected to ground, probe ISC motor relay connector cavity ignition feed circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 12 .
7. Using DVOM, measure resistance between ISC motor relay terminals No. 3 (Gray wire) and No. 4 (White/Blue wire). See WIRING DIAGRAMS article. If resistance is infinite, go to next step. If resistance is not infinite, go to step 13 .
8. Using DVOM, measure resistance between ISC terminals No. 1 (White/Blue wire) and No. 2 (Gray/Black wire). See WIRING DIAGRAMS article. If resistance is 75-95 ohms, go to next step. If resistance is not 75-95 ohms, go to step 13 .
9. Turn ignition off. Disconnect PCM electrical connectors. Connect a fused jumper wire between battery voltage and ISC motor relay connector cavity ISC motor relay control circuit. See WIRING DIAGRAMS article. Using DVOM, measure voltage at PCM 26-pin connector (harness side) ISC motor relay control circuit. If battery voltage is present, go to next step. If battery voltage is not present, go to step 14 .
10. Turn ignition off. Connect ISC motor relay. Disconnect PCM 26-pin connector. Back out PCM 26-pin connector terminals No. 11 (Gray/Yellow wire), No. 16 (Gray/Black wire), and No. 24 (Gray/Red wire). Reconnect PCM connector with specified wire terminals removed. Connect a fused jumper wire between PCM 26-pin connector terminal No. 16 (Gray/Black wire) and ground. Turn ignition on, with engine off. Ensure ISC motor actuator plunger contacts throttle lever. Connect 4, NEW 1.5 volt batteries in series. Connect PCM 26-pin connector terminal No. 11 (Gray/Yellow wire) to negative side of batteries. Momentarily connect PCM 26-pin connector terminal No. 24 (Gray/Red wire) to positive side of batteries. If ISC motor plunger retracts, go to next step. If ISC motor plunger does not retract, go to step 15 .
11. Turn ignition off. Disconnect 1.5 volt batteries and reinstall PCM 26-pin connector terminals No. 11 (Gray/Yellow wire), No. 16 (Gray/Black wire), and No. 24 (Gray/Red wire). Turn ignition on, with engine off. Using test light connected to battery voltage, probe ISC motor connector ISC motor ground circuit. See WIRING DIAGRAMS article. If test light illuminates, go to step 17 . If test light does not illuminate, go to step 16 .
12. Repair open in ignition feed circuit between ISC motor relay and main relay located in relay box, in left side of engine compartment. After repairs, go to step 19 .
13. Replace ISC motor relay. After repairs, go to step 19 .
14. Repair open or short in ISC motor relay control circuit between ISC motor relay and PCM. After repairs, go to step 19 .
15. Check for an open or short in ISC motor control circuits (Gray/Yellow wire, Gray/Red wire and Gray wire). Repair as necessary. After repairs, go to step 19 . If circuits are okay, go to step 18 .
16. Repair open in ISC motor ground circuit. After repairs, go to step 19 .
17. Replace PCM. Program PCM using required equipment. After replacing PCM, go to step 19 .
18. Replace ISC motor. After repairs, go to next step.
19. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

If DTC P0510 is also set, diagnose DTC before continuing. Ensure throttle plate is not stuck or binding, and movement is smooth and even. Check throttle cable adjustment. Ensure correct PCV valve is installed and no vacuum leaks are present. Check Throttle Position (TP) sensor for accuracy. Using scan tool, ensure ISC duty cycle parameter is 20-40 percent at normal engine operating temperature.

Check for a poor PCM electrical connection. Check for damaged wiring harness. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

PCM control Idle Air Control (IAC) valve to regulate air flow through idle air by-pass passage. Idle speed is determined by the amount of air flowing through idle air by-pass passage. IAC valve is regulated according to engine load. A malfunctioning IAC valve could cause a stalling condition. DTC P0507 will set when TP sensor indicates a closed throttle position with engine coolant temperature greater than 176°F (80°C) and engine idle speed is 200 RPM or greater than desired idle. When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Start engine and allow it to reach normal operating temperature. Turn off all electrical accessories. Using scan tool, monitor IAC duty cycle parameter. If scan tool indicates IAC duty cycle is 8-25 percent, go to «DIAGNOSTIC AIDS»(ref-189-S38681333292000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article. If scan tool does not indicate IAC duty cycle is 8-25 percent, go to next step.
3. Check for vacuum leaks, PCV valve for a good seal and operation, and split or damaged vacuum lines and hoses. Repair as necessary. After repairs, go to step 14 . If no problem is found, go to next step.
4. Disconnect IAC valve electrical connector. Turn ignition on, with engine off. Using test light connected to ground, probe IAC valve connector (harness side) IAC valve battery voltage circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 6 .
5. Using DVOM, probe IAC valve connector (harness side) IAC valve battery voltage circuit. See WIRING DIAGRAMS article. If battery voltage is present, go to step 7 . If battery voltage is not present, go to next step.
6. Repair open or short in IAC valve battery voltage circuit between IAC valve and main relay located in relay box, in left side of engine compartment. After repairs, go to step 14 .
7. Using test light connected to battery voltage, probe IAC valve connector (harness side) IAC valve ground circuit. See WIRING DIAGRAMS article. If test light illuminates, go to step 9 . If test light does not illuminate, go to next step.
8. Repair open in IAC valve ground circuit between IAC valve and ground connection. After repairs, go to step 14 .
9. Turn ignition off. Connect IAC valve electrical connector to IAC valve. Disconnect PCM 22-pin connector. Back out PCM 22-pin connector IAC valve control circuit terminal. Reconnect PCM connector with IAC valve control circuit wire terminal removed. Turn ignition on, with engine off. Using DVOM, probe PCM 22-pin connector IAC valve control circuit. See WIRING DIAGRAMS article. If battery voltage is present, go to next step. If battery voltage is not present, go to step 11 .
10. Start engine. Using scan tool, monitor engine speed parameter. Using test light connected to ground, momentarily probe PCM 22-pin connector IAC valve control circuit. See WIRING DIAGRAMS article. If engine speed fluctuates when test light contacts IAC valve control circuit, go to step 13 . If engine speed does not fluctuate when test light contacts IAC valve control circuit, go to step 12 .
11. Check for a short to voltage in IAC valve control circuit between IAC valve and PCM. Repair as necessary. After repairs, go to step 14 . If circuit is okay, go to next step.
12. Replace IAC valve. After repairs, go to step 14 .
13. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
14. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Ensure engine idle speed is correct. Check for foreign objects blocking IAC passage or throttle bore. Check throttle plate for smooth and even movement. Check IAC passage, throttle bore, and throttle plate for excessive deposits. Check throttle cable for correct adjustment and free-play. Ensure correct PCV valve is installed, brake booster hose is not disconnected, and no vacuum leaks are present.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Closed Throttle Position (CTP) switch is located in Idle Speed Control (ISC) motor. ISC motor sends a CTP switch signal to PCM. PCM applies 5 volts to CTP switch. CTP switch is closed with engine idling (low voltage signal at PCM) and open with engine RPM greater than idle (high voltage signal at PCM). When PCM detects a low voltage signal throttle valve is closed, and when high voltage signal is detected throttle valve is open. DTC P0510 will set when vehicle speed changes from 0-20 MPH 16 times per ignition cycle and CTP switch did not indicate an off/on cycle during change in vehicle speed. When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Turn ignition on, with engine off. Using scan tool, clear DTC information. Using scan tool, monitor CTP switch parameter. With throttle in closed position (idle), scan tool should indicate IDLE. With throttle in open position, scan tool should indicate NOT IDLE. If CTP switch parameter is as specified, go to next step. If CTP switch parameter is not as specified, go to step 4 .
3. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If DTC P0510 resets, go to next step. If DTC P0510 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S42218252852000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
4. Disconnect ISC motor electrical connector. Using DVOM, measure voltage between ground and ISC motor connector (harness side) 5-volt reference voltage circuit. See WIRING DIAGRAMS article. If voltage is about 5 volts, go to next step. If voltage is not about 5 volts, go to step 7 .
5. Using test light connected to battery voltage, probe ISC motor connector (harness side) ISC motor ground circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 8 .
6. Using scan tool, monitor CTP switch parameter. With ISC motor harness connector disconnected, CTP switch parameter should indicate NOT IDLE. Using a fused jumper wire, connect ISC motor connector (harness side) CTP switch signal circuit and ISC motor ground circuit. See WIRING DIAGRAMS article. CTP switch parameter should indicate IDLE. If CTP switch parameter is as specified, go to step 10 . If CTP switch parameter is not as specified, go to step 9 .
7. Repair open or short in 5-volt reference voltage circuit. After repairs, go to step 12 .
8. Repair poor connection or open in ISC motor ground circuit. After repairs, go to step 12 .
9. Check for an open or short in CTP switch signal circuit between ISC motor and PCM. Repair as necessary. After repairs, go to step 12 . If circuit is okay, go to step 11 .
10. Replace ISC motor. After repairs, go to step 12 .
11. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
12. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

If DTC P0107, P0122, P0450 and P0510 are set together, check for an open in 5-volt reference voltage circuit. DTC P0510 could set if Throttle Position (TP) sensor is incorrectly adjusted.

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

PCM has detected a communication circuitry failure. DTC P0601 will set when an EEPROM programing error is detected. When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Using scan tool, clear DTC information. Turn ignition on to initialize PCM. Start engine. Road test vehicle. If necessary, repeat road test. If vehicle does not start, crank engine so that DTC P0601 can set. If DTC P0601 resets, go to next step. If DTC P0601 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S32990228262000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
3. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
4. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Check PCM for water contamination. Water contamination could cause damage and corrosion to circuit boards and internal components. Repair source of water contamination before PCM replacement.

PCM has detected a communication circuitry failure. DTC P0603 will set when an EEPROM data readout error is detected. When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Using scan tool, clear DTC information. Turn ignition on to initialize PCM. Start engine. Road test vehicle. If necessary, repeat road test. If vehicle does not start, crank engine so that DTC P0603 can set. If DTC P0603 resets, go to next step. If DTC P0603 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S37976623062000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
3. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
4. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Check PCM for water contamination. Water contamination could cause damage and corrosion to circuit boards and internal components. Repair source of water contamination before PCM replacement.

EFE heater provides a source of rapid heat to air/fuel mixture during cold start conditions. Rapid heating provides uniform fuel distribution and reduces time that engine is in open loop operation. If engine RPM is greater than idle and PCM determines engine coolant temperature is below operating range, Positive Temperature Coefficient (PTC) heater relay (EFE heater relay) will energize. Voltage is now supplied to EFE heater. With engine at idle, or when engine coolant reaches normal operating temperature, PCM will de-energize EFE system. DTC P1250 will set when

1. Intake air temperature is 14-122°F (-10-50°C).
2. Barometric pressure is greater than 11 psi (75 kPa).
3. Fuel level is greater than 25 percent.
4. Resistor voltage is less than 2.5 volts for 5 seconds with EFE heater off.
5. Resistor voltage is .3 volt or more for 5 seconds with EFE heater on.

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If DTC P1250 resets, go to next step. If DTC P1250 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S16013948952000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
3. Start engine. Ensure engine coolant temperature is less than 176°F (80°C) and idle speed is greater than 800 RPM. Disconnect EFE heater relay. Using test light connected to battery voltage, probe EFE heater relay connector cavity EFE heater relay control circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 8 .
4. Using test light connected to ground, probe EFE heater relay connector cavity EFE heater relay ignition feed circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 9 .
5. Reconnect EFE heater relay. Using a fused jumper wire, backprobe between ground and EFE heater relay connector cavity EFE heater relay control circuit. See WIRING DIAGRAMS article. Using test light connected to ground, backprobe EFE heater relay connector cavity EFE heater relay battery feed circuit. If test light illuminates, go to next step. If test light does not illuminate, go to step 10 .
6. Using test light connected to ground, probe EFE heater connector EFE heater power feed circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 12 .
7. Check for a poor connection or open in EFE heater ground circuit. Repair as necessary. After repairs, go to step 15 . If circuit is okay, go to step 13 .
8. Check for an open in EFE heater relay control circuit between EFE heater relay and PCM. Repair as necessary. After repairs, go to step 15 . If circuit is okay, go to step 14 .
9. Repair open in EFE heater relay ignition feed circuit between EFE heater relay and main relay. After repairs, go to step 15 .
10. Check for an open in EFE heater relay battery feed circuit between EFE heater relay and fuse box located in left side of engine compartment. Repair as necessary. After repairs, go to step 15 . If circuit is okay, go to next step.
11. Replace EFE heater relay. After repairs, go to step 15 .
12. Repair open in EFE heater power feed circuit between EFE heater relay and EFE heater. After repairs, go to step 15 .
13. Replace EFE heater. After repairs, go to step 15 .
14. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
15. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. If DTC 1300 and 1310 are both set, go to step 11 . If only one DTC is set, go to next step.
3. Using scan tool, clear DTC information. Turn ignition off. Turn ignition on and attempt to start engine. If engine starts and runs smoothly for 4-5 seconds before stalling, go to step 9 . If engine does not start, go to next step.
4. Turn ignition off. Disconnect ignition coil electrical connector. Turn ignition on, with engine off. Using test light connected to ground, probe ignition coil connector ignition power circuit. See WIRING DIAGRAMS article. If test light illuminates, go to next step. If test light does not illuminate, go to step 7 .
5. Using DVOM, probe ignition coil connector ignition trigger signal circuit while cranking engine. See WIRING DIAGRAMS article. If voltage is 0.5-1.0 volt, go to next step. If voltage is not 0.5-1.0 volt, go to step 8 .
6. Using test light connected to battery voltage, probe ignition coil connector (harness side) ground. See WIRING DIAGRAMS article. If test light illuminates, go to step 16 . If test light does not illuminate, go to step 10 .
7. Repair open or short in ignition power circuit between ignition coil and splice connection SP260. After repairs, go to step 18 .
8. Check for an open or short in ignition trigger signal circuit between ignition coil and PCM. Repair as necessary. After repairs, go to step 18 . If circuit is okay, go to step 16 .
9. Check for an open in ignition fail-safe input circuit between ignition coil and splice connection SP260. Repair as necessary. After repairs, go to step 18 . If circuit is okay, go to step 16 .
10. Repair open in ignition ground circuit between ignition coil and ground connection. After repairs, go to step 18 .
11. Using scan tool, clear DTC information. Turn ignition off. Turn ignition on and attempt to start engine. If engine starts and runs smoothly for 4-5 seconds before stalling, go to step 14 . If engine does not start, go to next step.
12. Turn ignition off. Disconnect ignition coil electrical connector. Turn ignition on, with engine off. Using test light connected to ground, probe ignition coil connector ignition power circuit. See WIRING DIAGRAMS article. If test light illuminates, go to step 15 . If test light does not illuminate, go to next step.
13. Check for an open in ignition power circuit between splice connection SP260 and junction block No. 2. Check for a short in ignition power circuit between splice connection SP260, junction block No. 2 or noise filter. Check for a faulty noise filter. Repair or replace as necessary. After repairs, go to step 18 .
14. Check for an open in ignition fail-safe input circuit between PCM and splice connection SP260. Check for a short to ground in ignition fail-safe input circuit between PCM and ignition coils. Check for a short to voltage in ignition fail-safe input circuit between PCM and ignition coils. Repair or replace as necessary. After repairs, go to step 18 . If circuit is okay, go to step 17 .
15. Repair faulty ignition coil ground circuits at ground connection G105. After repairs, go to step 18 .
16. Replace ignition coil. After repairs, go to step 18 .
17. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
18. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Check for a clean, tight ground connection. If DTC P1300 and P1310 are both set, fault is located in shared electrical circuit or components of ignition coils. If EFI relay remains energized after ignition is turned off, DTCs P1300 or P1310 may be set. Check noise filter for an internal short or low resistance. If noise filter is faulty, ignition coil may not receive adequate voltage during high load conditions.

PCM will wait to receive ignition fail safe signals before providing fuel injector operation unless ignition is cycled or DTCs are cleared. Check ignition coil resistance. Primary coil winding resistance is 4.8-5.2 k/ohms at 68°F (20°C) and secondary coil winding resistance is 12.7-13.7 k/ohms at 68°F (20°C).

An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Crankshaft Position (CKP) sensor is a magnetic generator type sensor. CKP sensor produces an alternating current signal which increases in both frequency and amplitude as engine RPM increases. CKP sensor sends a reference signal to PCM to indicate RPM and crankshaft position. Reference signal, along with Camshaft Position (CMP) sensor signal, is used by PCM to calculate fuel injection pulse, determine TDC for ignition timing, and establish a starting point for ignition coil and injection sequencing.

DTC P1335 will set when CKP sensor signal is not detected by PCM for over 50 milliseconds with engine speed greater than 1000 RPM. When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Operate vehicle within freeze frame conditions. If DTC P1335 resets, go to next step. If DTC P1335 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S33300284942000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
3. Turn ignition off. Disconnect CKP sensor electrical connector. Using DVOM, measure resistance of CKP sensor. If resistance is 985-1670 ohms at 122°F (50°C) or 1265-1890 ohms at 212°F (100°C), go to next step. If resistance is not as specified, go to step 6 .
4. Turn ignition off. Disconnect PCM 26-pin connector. Check for an open or short in CKP sensor circuit. See WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step 8 . If circuit is okay, go to next step.
5. Check for poor connections at CKP sensor and PCM. Repair as necessary. After repairs, go to step 8 . If connections are okay, go to step 7 .
6. Replace CKP sensor. After repairs, go to step 8 .
7. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
8. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

DTC P1335 can result from a defective reluctor wheel. Remove crankshaft sensor and inspect reluctor wheel through sensor hole. Check reluctor wheel for porosity, nicks, dents and any other damage. Repair as necessary.

An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

When engine is running and fuel level is lower than a specified value, EVAP tank pressure control solenoid vacuum valve is turned on by PCM. Vacuum is then applied to diaphragm of fuel tank pressure control valve, opening a passage and allowing fuel vapors to flow between fuel tank and charcoal canister. DTC P1410 will set when engine is running at a steady speed, operating in closed loop, fuel level is 25-75 percent, and a low voltage is indicated in solenoid control circuit with fuel level is higher than a specified value when diagnostic runs. When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of diagnostic failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Remove rear seat cushion. Disconnect fuel tank EVAP solenoid harness electrical connector C311. Turn ignition on, with engine off. Connect a test light between ignition positive voltage terminal and EVAP tank pressure control solenoid vacuum valve control circuit terminal of connector C311 (body harness side). See WIRING DIAGRAMS article. Using scan tool, command EVAP tank pressure control solenoid vacuum valve on and off while observing test light. If test light illuminates only when solenoid is commanded on, go to step 4 . If test light does not illuminate, go to next step.
3. Check for an open in EVAP fuel tank pressure control solenoid vacuum valve ignition positive voltage circuit. Check for an open or short in EVAP fuel tank pressure control solenoid vacuum valve control circuit between PCM and solenoid vacuum valve. Repair as necessary. After repairs, go to step 11 . If circuit is okay, go to step 10 .
4. Remove fuel tank. Check EVAP fuel tank pressure control solenoid vacuum valve for poor connections. Repair as necessary. After repairs, go to step 11 . If circuit is okay, go to next step.
5. Remove EVAP fuel tank pressure control solenoid vacuum valve. Using DVOM, measure resistance of EVAP fuel tank pressure control solenoid vacuum valve. If resistance is 30-34 ohms at 68°F (20°C), go to next step. If resistance is not 30-34 ohms at 68°F (20°C), go to step 9 .
6. Blow air into side port of EVAP fuel tank pressure control solenoid vacuum valve. If air passes through valve and out top port of EVAP fuel tank pressure control solenoid vacuum valve, go to step 9 . If air does not pass through valve and out top port of EVAP fuel tank pressure control solenoid vacuum valve, go to next step.
7. Apply 12 volts to EVAP fuel tank pressure control solenoid vacuum valve. Blow air into side port of EVAP fuel tank pressure control solenoid vacuum valve. If air passes through valve and out top port of EVAP fuel tank pressure control solenoid vacuum valve, go to next step. If air does not pass through valve and out top port of EVAP fuel tank pressure control solenoid vacuum valve, go to step 9 .
8. Check for an open or short in EVAP fuel tank pressure control solenoid vacuum valve wiring harness between solenoid vacuum valve and connector C311 (body harness). Repair as necessary. After repairs, go to step 11 . If circuit is okay, go to «DIAGNOSTIC AIDS»(ref-189-S02130097302000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
9. Replace EVAP fuel tank pressure control solenoid vacuum valve. After repairs, go to step 11 .
10. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
11. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

A faulty fuel level sensor may cause a DTC P1410 to set. Check for a poor PCM electrical connection. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Barometric pressure sensor and circuitry are located within PCM. Barometric pressure sensor represents barometric pressure and is used to compensate for altitude changes. Barometric pressure sensor reading is displayed from PCM using a scan tool when ignition is on and engine is off. DTC P1450 will set when

1. Barometric pressure is less than 4.9 psi (33 kPa) with ignition on and engine cranked for 2 seconds.
2. Barometric pressure is 19.7 psi (136 kPa) or more with ignition on and engine cranked for 2 seconds.

When DTC sets, MIL will illuminate. PCM will record operating conditions at time of diagnostic failure and store information in freeze frame buffer. PCM will enter Fail-Safe Function using barometric pressure value of 14.5 psi (100 kPa).

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If DTC P1450 resets, go to next step. If DTC P1450 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S08425822642000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
3. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
4. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Barometric pressure varies depending on weather conditions and altitude.

Barometric pressure sensor and circuitry are located within PCM. Barometric pressure sensor represents barometric pressure and is used to compensate for altitude changes. Barometric pressure sensor reading is displayed from PCM using a scan tool when ignition is on and engine is off. DTC P1451 will set when difference between barometric pressure and manifold absolute pressure is 3.8 psi (26 kPa) or more with ignition on and engine cranked for 2 seconds. When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of diagnostic failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Check for MAP sensor DTC P0106, P0107 or P0108. If MAP sensor DTC is set, diagnose DTC(s). If no other DTC is set, go to next step.
3. Turn ignition on, with engine off. Using scan tool, clear DTC information. Operate vehicle within freeze frame conditions. If DTC P1451 resets, go to next step. If DTC P1451 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S06026663192000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
4. Turn ignition on, with engine off. Using scan tool, monitor MAP sensor parameter. If MAP sensor (barometric pressure) display is about 14.5 psi (100 kPa), go to next step. If MAP sensor display is not about 14.5 psi (100 kPa), go to «DIAGNOSTIC AIDS»(ref-189-S06026663192000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
5. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
6. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Barometric pressure varies depending on weather conditions and altitude. A faulty or skewed Manifold Absolute Pressure (MAP) sensor may cause a DTC P1451 to set. If DTC P1451 can not be duplicated, information in freeze frame data can be useful in determining vehicle operating conditions when DTC was initially set.

During engine cranking, battery voltage is applied to PCM. Starter signal is mainly used to increase fuel injection volume for starting injection control. This signal is sent from Transaxle Range (TR) switch (A/T) or Clutch Pedal Position (CPP) switch (M/T). If signal is not detected during ignition, PCM will still allow engine to start. DTC P1500 will set when

1. No signal is detected by PCM with starter engaged (once per drive cycle for .4 second).
2. Low signal voltage at PCM while engine cranking (once per drive cycle for .4 second).
3. High signal voltage at PCM after engine starts (once per drive cycle for .4 second).

When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool, clear DTC information. Start engine twice. Repeat if necessary. If DTC P1500 resets, go to next step. If DTC P1500 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S32658264292000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
3. Turn ignition on, with engine off. Using DVOM connected to ground, backprobe PCM 16-pin connector CPP/TR switch input circuit. See WIRING DIAGRAMS article. Crank engine with gear selector in Park or Neutral (A/T) or clutch pedal fully depressed (M/T). If voltage is 6-12 volts while cranking engine, go to step 5 . If voltage is not 6-12 volts while cranking engine, go to next step.
4. Repair open or short in CPP/TR switch input circuit between TR switch (A/T) or CPP switch (M/T), and PCM. After repairs, go to step 9 .
5. With DVOM still connected to PCM 16-pin connector CPP/TR switch input circuit and ground, measure voltage with engine running. If voltage is zero volts with engine running, go to step 7 . If voltage is more than zero volts with engine running, go to next step.
6. Repair short to voltage in CPP/TR switch input circuit between TR switch (A/T) or CPP switch (M/T), and PCM. After repairs, go to step 9 .
7. Check for poor connection at PCM. Repair as necessary. After repairs, go to step 9 . If connection is okay, go to next step.
8. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
9. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Battery voltage is supplied to PCM for retention of certain long term memory data. DTCs and values for engine controls learned by PCM are kept in PCM memory with ignition on or off. DTC P1510 sets and PCM long term memory information is lost when memory power input circuit voltage is interrupted. DTC P1510 will set when no back-up power is supplied to PCM for 5 seconds after starting engine. When DTC sets, MIL will illuminate. PCM stores DTC P1510 as long as ignition is not turned off.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Start engine and run for at least one minute. Disconnect IAT sensor electrical connector. Observe MIL. Reconnect IAT sensor electrical connector. Turn ignition off. Wait for at least one minute. Turn ignition on, with engine off. Using scan tool, check for DTCs. If DTC P0113 is set, go to «DIAGNOSTIC AIDS»(ref-189-S09743723922000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article. If DTC P0113 is not set, go to next step.
3. Turn ignition off. Disconnect PCM 26-pin connector. Using DVOM, measure voltage between ground and PCM 26-pin connector battery positive voltage circuit. See WIRING DIAGRAMS article. If battery voltage is present, go to step 5 . If battery voltage is not present, go to next step.
4. Check for open or short in battery positive voltage circuit between PCM and junction block located behind left side of instrument panel. Repair as necessary. After repairs, go to step 7 . If circuit is okay, go to «DIAGNOSTIC AIDS»(ref-189-S09743723922000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
5. Check for poor connection at PCM. Repair as necessary. After repairs, go to step 7 . If connection is okay, go to next step.
6. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
7. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

With no back-up power supplied to PCM, DTC P1510 will only remain in PCM memory with ignition on. When ignition is turned off, PCM will lose memory and DTC P1510 will not be stored. Ensure all fuses are okay. Replace as necessary. An intermittent malfunction may be caused by a poor connection, rubbed-through wire insulation, or a wire broken inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

PCM receives an on/off signal from stoplight switch. When PCM receives an off signal from stoplight switch, PCM will allow A/T Torque Converter Clutch (TCC) to lock-up. PCM also uses stoplight switch input for fuel cut-off control. DTC P1520 will set when vehicle speed is greater than 19 MPH and stoplight switch remains on. When DTC sets, MIL will illuminate after 2 consecutive ignition cycles in which diagnostic runs with active fault. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Turn ignition off. Ensure brake pedal is released and check operation of rear stoplights. If rear stoplights are illuminated, go to next step. If rear stoplights are not illuminated, go to step 5 .
3. Disconnect stoplight switch electrical connector. Check operation of rear stoplights. If stoplights are illuminated, go to next step. If stoplights are not illuminated, go to step 7 .
4. Turn ignition off. Disconnect PCM 22-pin connector. With stoplight switch disconnected and using DVOM, measure voltage at stoplight switch connector brake signal circuit. See WIRING DIAGRAMS article. If voltage is zero volts, go to step 8 . If voltage is more than zero volts, go to step 10 .
5. Using a scan tool, monitor TCC brake switch parameter. Ensure brake pedal is released. If scan tool indicates stoplight switch is in released position, go to «DIAGNOSTIC AIDS»(ref-189-S20303226502000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article. If scan tool does not indicate stoplight switch is released, go to next step.
6. Turn ignition off. Disconnect PCM 22-pin connector. Back out PCM 22-pin connector brake signal circuit terminal. See WIRING DIAGRAMS article. Reconnect PCM connector with brake signal circuit wire terminal removed. Using scan tool, monitor TCC brake switch parameter. If scan tool indicates stoplight switch is in released position, go to step 8 . If scan tool does not indicate stoplight switch is released, go to step 10 .
7. Check for a misadjusted stoplight switch. If stoplight switch is out of adjustment, go to step 11 . If stoplight switch adjustment is okay, go to step 9 .
8. Repair short to voltage in brake signal circuit between PCM and stoplight switch. After repairs, go to step 11 .
9. Replace stoplight switch. After repairs, go to step 11 .
10. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
11. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.

Test switch terminal is located in duty check DLC behind glove box. When test switch terminal is grounded, PCM fixes ignition timing to base timing. DTC P1530 will set when vehicle speed is greater than one MPH and test switch terminal is on (circuit grounded) for 5 seconds. When DTC sets, MIL will illuminate. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Using scan tool, clear DTC information. Start engine. Using scan tool, monitor spark advance adjust test switch parameter. If scan tool indicates spark advance adjust test switch is on, go to next step. If scan tool does not indicate spark advance adjust test switch is on, go to «DIAGNOSTIC AIDS»(ref-189-S36382953952000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
3. Turn ignition on, with engine off. Using DVOM connected to ground, measure voltage at duty check DLC test switch signal circuit. See WIRING DIAGRAMS article. If voltage is 5 volts, go to «DIAGNOSTIC AIDS»(ref-189-S36382953952000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article. If voltage is not 5 volts, go to next step.
4. Check for a short to ground in test switch signal circuit. Repair as necessary. After repairs, go to step 6 . If circuit is okay, go to next step.
5. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
6. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

Check wiring harness for damage causing a short to ground. Wiggle wiring harness to duty check DLC while engine is running. Using scan tool, monitor spark advance adjust test switch parameter for an ON display, indicating wiring harness is shorting to ground.

Battery voltage is supplied to PCM with ignition on or off for use by PCM keep-alive memory and air/fuel ratio adaptive control valve memory. DTC P1600 will set when no battery voltage is present at PCM battery positive voltage circuit. When DTC sets, MIL will illuminate. PCM will record operating conditions at time of failure and store information in freeze frame buffer.

1. Perform On-Board Diagnostic (OBD) system check. See «ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-189-S28417016012000030800000) under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
2. Connect scan tool to DLC. Turn ignition on, with engine off. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Start engine and allow it to reach normal operating temperature. If DTC P1600 resets, go to next step. If DTC P1600 does not reset, go to «DIAGNOSTIC AIDS»(ref-189-S26938058092000030800000) . Check for an intermittent problem. See appropriate TROUBLE SHOOTING - NO CODES article.
3. Check for an open EFI fuse or poor connections at fuse/relay block No. 1 located in left side of engine compartment, near air cleaner. Repair as necessary. After repairs, go to step 7 . If no problem is found, go to next step.
4. Turn ignition off. Disconnect PCM 22-pin connector. Turn ignition on, with engine off. Using DVOM, measure voltage at PCM 22-pin connector (harness side) battery positive voltage circuit. See WIRING DIAGRAMS article. If battery voltage is present, go to step 6 . If battery voltage is not present, go to next step.
5. Repair open in battery positive voltage circuit between PCM and fuse/relay block No. 1. After repairs, go to step 7 .
6. Replace PCM. Program PCM using required equipment. After replacing PCM, go to next step.
7. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose DTC(s).

If DTC P1600 is set, PCM will not store another DTC. An intermittent condition may be caused by poor connection, rubbed-through insulation, or a broken wire inside insulation. Check PCM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, or poor terminal-to-wire connections before component replacement.