Engine Controls - Tests W/codes: Diagnosis Oldsmobile Aurora I

SELF-DIAGNOSTIC SYSTEM

Note. Powertrain Control Module (PCM) may also be referred to as Vehicle Control Module (VCM) in some diagnostic text and illustrations. Terms may be used interchangeably.

PCM/VCM is equipped with a self-diagnostic system, which detects system failures or abnormalities. When a malfunction occurs, PCM/VCM will store a Diagnostic Trouble Code (DTC) and, in most cases, illuminate the Malfunction Indicator Light (MIL) located on instrument panel. Malfunctions are recorded as hard failures or as intermittent failures.

THERE ARE 4 TYPES OF DTC CATEGORY

1. Type "A" Emissions related, turns on MIL the first time DTC sets.
2. Type "B" Emissions related, turns on MIL if fault is active for 2 consecutive driving cycles.
3. Type "C" Non-emissions related, does not turn on MIL, but will turn on SERVICE light.
4. Type "D" Non-emissions related, does not turn on MIL or SERVICE light.

DTC STATUS

This selection will display any DTC(s) that have not run during the current ignition cycle or have reported a test failure during this ignition up to a maximum of 33 DTCs. DTC test which run and passed will cause that affected DTC to be removed from scan tool screen.

LAST TEST FAIL

This selection will display only DTCs that have failed the last time the test ran. The last test may have ran during the previous ignition cycle, if a type "A" or "B" DTC is displayed. For type "C" DTCs, the last failure must have occurred during the current ignition cycle to be displayed as LAST TEST FAIL.

TEST FAIL SCC

Test Fail Since Code Clear selection will display all active and history DTCs that have reported a test failure since the last time DTCs were cleared. DTCs that last failed over 40 warm-up cycles before this option is selected will not be displayed.

TEST RAN AND PASSED

This message indicates the selected diagnostic test has

1. Passed the last test.
2. Ran and passed during this ignition cycle.
3. Ran and passed since DTCs were last cleared.
4. Test has not failed since DTCs were last cleared.

If this message is displayed, repair is done. If FAILED THIS IGN. message is displayed, repair is incomplete and further diagnosis is required.

DIAGNOSTIC PROCEDURE

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

1. Ensure all engine systems not related to computer system are operating properly. DO NOT proceed with testing unless all other problems have been repaired. ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK must be performed before using specific DTC testing procedure. See appropriate OBD SYSTEM CHECK procedure in appropriate BASIC TESTING article.
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-20306-S40394827982001010200000) . For diagnosing hard codes, proceed to appropriate DTC test. For diagnosing intermittent codes, proceed to INTERMITTENTS in appropriate TESTS W/O CODES article.
3. If no DTCs are present and a driveability problem exists, refer to SYMPTOMS in appropriate TESTS W/O CODES article. Doing so will help identify proper system or component to check in appropriate SYSTEM/COMPONENT TESTS article.
4. After necessary repairs are made, clear DTCs, verify vehicle will enter "closed loop" operation and ensure DTC does not reset.

READING TROUBLE CODES

Note. Use of Tech 1 scan tool is required to retrieve DTCs. Refer to user reference manuals supplied with scan tool.

TROUBLE CODE DEFINITION

TROUBLE CODE DEFINITION

HARD OR INTERMITTENT TROUBLE CODE DETERMINATION

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 DIAGNOSTIC TROUBLE CODES (DTC)»(ref-20306-S07805338752001010200000) .
2. Apply parking brake, and place transmission in Neutral or Park. Block drive wheels, and start engine. MIL should go out. Run warm engine at specified RPM for 2 minutes and note MIL.
3. If MIL comes on, 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 trouble codes were cleared.
4. If MIL does not come on, all stored DTCs were intermittent failures, except as noted above.

Note. DTCs will be recorded at various operating times. Some codes require operation of that 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.

CLEARING DIAGNOSTIC TROUBLE CODES (DTC)

To clear DTCs from memory, either to determine if malfunction will occur again or after making necessary repairs, disconnect power supply to PCM/VCM for at least 30 seconds or clear codes using a scan tool.

Diagnostic Aids

Diagnostic aids are additional tips used to help diagnose trouble codes when inspected circuit is okay. Diagnostic aids may help lead to a definitive solution to trouble code problem.

SPECIAL TOOLS (DIAGNOSTIC)

Note. A scan tool plugged into DLC is used to read DTCs and check voltages in system on serial data line. A scan tool is REQUIRED to retrieve vehicle information.

Computerized engine control system is most easily diagnosed using scan tool; however, other tools may aid in diagnosing problems. These tools are a tachometer, test light, ohmmeter, digital voltmeter with a 10-megohm input impedance (minimum), vacuum pump, vacuum gauge, fuel injector test lights and 6 jumper wires 6" long (one wire with female connectors at both ends, one wire with male connectors at both ends and 4 wires with male and female connectors at opposite ends). A test light, rather than a voltmeter, must be used when indicated by a diagnostic test. In addition, special jumper harnesses or testers may be required by manufacturer to facilitate diagnosis.

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 DIAGNOSTIC CIRCUIT CHECK or ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK located in appropriate BASIC TESTING article. If vehicle does not pass OBD system check, information received may be invalid.

Scan tool is a specialized tester which, when plugged into DLC, can be used to diagnose on-board computer control systems by providing instant access to circuit voltage information without need to crawl under dash or hood to backprobe sensors and connectors.

Scan tool cuts down diagnostic time dramatically by furnishing input data (voltage signals) which can be compared to specification parameters. See SCAN DATA . They may also furnish information on output device (solenoids and motors) status. However, status parameters only indicate output signals have been sent to devices by PCM/VCM; they do not indicate whether devices have responded properly to signal. Verify proper response at output device using a voltmeter or test light.

A problem may exist even if DTCs are not present. About 80 percent of driveability problems occur without DTCs. Sensors that are out of calibration will not set a DTC but will cause driveability problems.

Using a scan tool is the easiest method of checking sensor specifications and other data parameters. 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 SCAN DATA .

Note. If erroneous voltage signals are suspected, verify tester information using a digital voltmeter and wiring schematic. If non-existent codes are displayed, DO NOT use scan tool for diagnosis. Contact tester manufacturer for additional information.

DIAGNOSTIC TROUBLE CODES

Note. In following diagnostic tests, schematics are courtesy of General Motors Corp.

Note. Before clearing DTCs, perform On-Board Diagnostic (OBD) system check. See appropriate BASIC TESTING article. Record FREEZE FRAME and FAILURE RECORDS for reference during testing. Data will be erased when DTCs are cleared.

Note. If VCM/PCM is replaced, NEW VCM/PCM must be programmed using special manufacturer's equipment.

Circuit Description

This test determines if MAF sensor is providing proper readings to the PCM. MAF sensor is a high frequency device that measures the rate of airflow through the throttle body. MAF sensor outputs a series of pulses that varies in frequency with airflow. PCM uses this signal for fuel control.

MAF sensor readings during acceleration will be much higher than those during deceleration or idle. PCM calculates what MAF sensor reading should be from the sensor under certain conditions using engine speed (RPM), throttle position, and altitude parameters. When these test conditions are met, PCM will compare its calculated MAF value to the actual value received from the sensor. The calculated MAF reading is calculated by comparing MAP, RPM and IAT values. If difference between calculated MAF and actual MAF is too great, DTC will set.

Diagnostic Procedures

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check for stored DTC(s). If DTC P0401, P0441, P1108, P1406, P1441, P1442, P1508, P1509 or P1645 is also present, diagnose affected DTC(s) first. If DTC(s) are not present or after diagnosing affected DTC(s), go to next step.
3. Check air (vacuum) leaks at MAF sensor seal, throttle body spacer, intake manifold, PCV, EGR valve, plate or tubes and brake booster and hoses. Repair as necessary and retest. If air leak is not found, go to next step.
4. Check for stuck or incorrect PCV valve. Check for air (unmetered) leaks at oil dipstick tube or oil filler cap. Repair as necessary and retest. If vacuum leak is not found, go to next step.
5. Using FREEZE FRAME and FAILURE RECORDS data function on scan tool, duplicate conditions under which DTC P0101 was set. If DTC resets, go to next step. If DTC does not reset, see DIAGNOSTIC AIDS.
6. Go to DTC P0106 and perform diagnostic table, then return to this step. If repairs were necessary, verify repairs and retest. If repairs were not necessary, go to next step.
7. Replace MAF sensor and retest.

For intermittent setting of DTC P0101, use FREEZE FRAME data under which the DTC set, looking for faulty data from other sensors which may set this DTC. An improperly installed air cleaner or a distorted snorkel may cause DTC to set. Check for proper air cleaner or snorkel installation.

DTC P0101 Schematic. Scheme 5

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Start engine. Using scan tool, check MAF sensor reading. If reading is 1.3 gm/sec or less, go to next step. If reading is greater than 1.3 gm/sec, fault is not present.
3. Turn ignition off. Disconnect MAF sensor harness connector. Turn ignition on. Using DVOM, check voltage between ground and MAF sensor input circuit at PCM harness connector terminal. If voltage is 4-6 volts, go to next step. If voltage is not as specified, go to step 6).
4. Check voltage between ground and MAF sensor power circuit at MAF sensor harness connector. If voltage is less than 10 volts, go to step 7). If voltage is 10 volts or greater, go to next step.
5. Measure voltage between MAF sensor harness connector ground and power circuits. If voltage is within 0.5 volt of voltage measured in step 4), go to step 9). If not, go to step 8).
6. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Using DVOM, check MAF sensor input circuit for open or short to ground. If repairs are necessary, repair as necessary and verify repair. If input circuit is okay, go to step 11).
7. Repair open or short to ground in MAF sensor power feed circuit.
8. Repair open or high resistance in MAF sensor ground circuit.
9. Check terminal contact at MAF sensor. Repair as necessary. If terminal contact is okay, go to next step.
10. Replace MAF sensor.
11. Check terminal contact of MAF sensor input circuit at PCM harness connector. Repair as necessary. If terminal contact is okay, go to next step.
12. Replace PCM. Program replacement PCM using required equipment.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, select FREEZE FRAME function under SPECIFIC DTC. Duplicate conditions under which DTC was set. If DTC resets, go to next step. If DTC does not reset, see DIAGNOSTIC AIDS.
3. Check terminal contact at MAF sensor connector. Repair as necessary. If terminal contact is okay, go to next step.
4. Replace MAF sensor.

Check for Electromagnetic Interference (EMI) on MAF sensor wires, caused by wiring being too close to spark plug wires or high-power transmitters (mobile radio) operating in the vicinity. A battery charger may also set this DTC.

This test determines when the MAP sensor is sticking. The PCM does this by checking for throttle position changes that are not immediately followed by MAP signal changes. When a throttle position change of 3.2 degrees within .5 second occurs, the PCM watches the MAP signal for one second following the throttle position change. If MAP signal does not change by at least 4 kPa in this period and MAP sensor reading is greater than 17.3 kPa than the expected MAP reading (based on engine speed and throttle position), DTC will set.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, select FREEZE FRAME function under DTC mode. Note MAP value reading. If MAP value is .08 volt or less, perform DTC P0107 tests. If MAP value is greater than .08 volt, go to next step.
3. Check terminal contact at MAP sensor connector and PCM. Repair as necessary. If terminal contact is okay, go to next step.
4. Replace MAP sensor.

DTC P0105 Schematic. Scheme 6

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. If DTC P0300 is also present, diagnose this DTC first. If DTC P0300 is not present, go to next step.
3. Connect scan tool. Turn ignition on, with engine off. Using scan tool, select ENGINE 1 function and note MAP display value. If MAP value is greater than 75 kPa (95 kPa at sea level), go to next step. If MAP value is less than specification, go to step 7).
4. Disconnect vacuum hose at MAP sensor. Connect a hand-held vacuum pump to MAP sensor. Slowly apply 20 in. Hg to sensor and note MAP display. Each one in. Hg applied to MAP sensor should result in a 4 kPa drop in MAP sensor reading. Watch for erratic reading. If reading is erratic, go to step 7). If reading changes smoothly, go to next step.
5. If MAP sensor reading is 34 kPa or less with 20 in. Hg applied to sensor, go to next step. If MAP sensor reading is greater than 34 kPa with 20 in. Hg applied, go to step 7).
6. Remove vacuum from MAP sensor. If MAP sensor reading returns to original value, see DIAGNOSTIC AIDS. If MAP sensor reading does not return to original value, go to next step.
7. Replace MAP sensor.

Check for poor or open ground circuit causing an intermittent signal problem.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, select ENGINE 1 and note MAP display. If MAP value displayed is 17 kPa or less, go to next step. If MAP value displayed is greater than 17 kPa, see DTC P0106 for diagnosis.
3. Turn ignition off. Disconnect MAP sensor harness connector. Jumper MAP sensor harness connector 5-volt reference terminal to signal circuit terminal. Turn ignition on. If scan data displays a value greater than 102 kPa, go to step 13). If scan data displays a value of 102 kPa or less, go to next step.
4. Remove jumper wire. Using DVOM, check voltage between MAP sensor harness connector 5-volt reference terminal and ground. If voltage reading is 4.5 volts or greater, go to next step. If voltage reading is less than 4.5 volts, go to step 7).
5. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM connector C1. Using DVOM, check resistance between ground and MAP sensor signal circuit in PCM harness connector C1. If resistance is 10,000 ohms or greater, go to next step. If resistance is less than 10,000 ohms, go to step 9).
6. Check resistance between MAP sensor signal circuit in PCM harness connector C1 and MAP sensor signal circuit at harness connector. If resistance is 5 ohms or greater, go to step 10). If resistance is less than 5 ohms, go to step 15).
7. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM connector C1. Using DVOM, check resistance between MAP sensor 5-volt reference circuit and ground. If resistance is 10,000 ohms or greater, go to next step. If resistance is less than 10,000 ohms, go to step 12).
8. Check resistance between MAP sensor 5-volt reference circuit at sensor harness connector and PCM harness connector C1 terminal. If resistance is 5 ohms or greater, go to step 11). If resistance is less than 5 ohms, go to step 15).
9. Repair short to ground in MAP sensor signal circuit.
10. Repair open in MAP sensor signal circuit.
11. Repair open in MAP sensor 5-volt reference circuit.
12. Repair short to ground in MAP sensor 5-volt reference circuit.
13. Check terminal contact at MAP sensor. Repair as necessary. If terminal contact is okay, go to next step.
14. Replace MAP sensor.
15. Check terminal contacts at PCM connector C1. Repair as necessary. If terminal contacts are okay, go to next step.
16. Replace PCM. Program replacement PCM using required equipment.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on, engine off. Using scan tool, select ENGINE 1 and note MAP display. If MAP value displayed is 102 kPa or greater, go to next step. If MAP value displayed is less than specification, see DTC P0106 for diagnosis.
3. Turn ignition off. Disconnect MAP sensor harness connector. Ignition on. If MAP sensor value is less than 16 kPa, go to next step. If MAP sensor value is greater than 16 kPa, go to step 5).
4. Using DVOM, check voltage between MAP sensor harness connector terminal "C" and ground. If voltage reading is 5.06 volts or greater, go to step 7). If voltage reading is less than 5.06 volts, go to step 8).
5. Check voltage between MAP sensor signal circuit and ground. If voltage reading is .5 volt or greater, go to next step. If voltage reading is less than .5 volt, go to step 10).
6. Repair short to voltage in MAP sensor signal circuit.
7. Repair short to battery voltage in MAP sensor 5-volt reference circuit.
8. Check terminal contact at MAP sensor. Repair as necessary. If terminal contact is okay, go to next step.
9. Replace MAP sensor.
10. Check MAP sensor signal circuit terminal contact at PCM harness connector C1. Repair as necessary. If terminal contacts are okay, go to next step.
11. Replace PCM. Program replacement PCM using required equipment.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. If DTC P0112 or P0113 is also present, diagnose affected DTC(s) first. If other DTC(s) are not present, go to next step.
3. Turn ignition on. Using scan tool, select FAILURE RECORD in DTC mode and note IAT snapshot display. If snapshot reading is less than -29°F (-34°C), go to next step. If snapshot reading is greater than -29°F (-34°C), go to step 5).
4. An intermittent high resistance reading occurred on IAT sensor circuit. Check for open in IAT ground circuit and IAT signal circuit. Repair as necessary. If circuits are okay, go to step 7).
5. If snapshot IAT sensor reading is greater than 291°F (144°C), go to next step. If reading is less than 291°F (144°C), go to step 7).
6. An intermittent low resistance reading occurred on the IAT sensor circuit. Check for possible short to ground in IAT sensor signal circuit. Repair as necessary. If circuit is okay, go to next step.
7. Artificially raise IAT temperature, from cool to warm. As IAT sensor warms, watch IAT sensor reading on scan tool. Look for a skip or jump in the value. If a skip or jump is noted, go to next step. If value did not skip or jump, see DIAGNOSTIC AIDS.
8. Replace IAT sensor.

Artificially changing the IAT temperature can be done by careful warming using heat gun or by cooling IAT in refrigerator, then allowing it to warm.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, select ENGINE 1 mode and note IAT display. If IAT temperature reading is 282°F (139°C) or greater, go to next step. If IAT temperature reading is less than 282°F (139°C), see DIAGNOSTIC AIDS.
3. Disconnect IAT sensor harness connector. If IAT temperature reading is 282°F (139°C) or greater, go to next step. If IAT temperature is less than 282°F (139°C), go to step 6).
4. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM connector. Using DVOM, check resistance between IAT signal circuit at harness connector and ground. If resistance is greater than 10,000 ohms, go to step 8). If resistance is less than 10,000 ohms, go to next step.
5. Repair short to ground in IAT sensor signal circuit.
6. Check terminal contact at IAT sensor. Repair as necessary. If terminal contact is okay, go to next step.
7. Replace IAT sensor.
8. Check terminal contact at PCM. Repair as necessary. If terminal contact is okay, go to next step.
9. Replace PCM. Program replacement PCM using required equipment.

IAT sensor can be damaged by backfire in intake manifold. If more than one IAT sensor has been replaced, check for signs of engine backfire.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, select ENGINE 1 mode and note IAT display. If IAT reading is -35°F (-37°C) or less, go to next step. If IAT reading is greater than -35°F (-37°C), see DIAGNOSTIC AIDS.
3. Disconnect IAT sensor harness connector. Using jumper wire, jumper IAT sensor harness connector terminals "A" and "B". If IAT reading is 247°F (147°C) or greater, go to next step. If IAT reading is less than 247°F (147°C), go to step 5).
4. Check terminal contact at IAT sensor. Repair as necessary. If terminal contact is okay, go to step 10).
5. Using jumper wire, jumper IAT sensor connector terminal "A" to ground. If IAT temperature reading is 247°F (147°C) or greater, go to next step. If IAT temperature reading is less than 247°F (147°C), go to step 7).
6. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Using DVOM, check resistance between IAT sensor ground circuit at harness connector and IAT sensor ground circuit to PCM connector C1. If resistance is greater than 5 ohms, go to step 8). If resistance is 5 ohms or less, go to next step.
7. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Using DVOM, check resistance between IAT harness connector terminal "A" and IAT sensor signal to PCM connector C2. If resistance is greater than 5 ohms, go to step 9). If resistance is 5 ohms or less, go to step 11).
8. Repair open in IAT sensor ground circuit.
9. Repair open in IAT sensor signal circuit.
10. Replace IAT sensor.
11. Check terminal contact at PCM harness connectors. Repair as necessary. If terminal contact is okay, go to next step.
12. Replace PCM. Program replacement PCM using required equipment.

IAT sensor can be damaged by backfire in intake manifold. If IAT sensor has been replaced more than once, check for signs of backfire.

Under severe cold weather conditions, this DTC could set if the actual outside temperature (IAT) is less than -35°F (-37°C) and ECT is at least 81°F (27°C) warmer than IAT.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. If DTC(s) P0117 or P0118 is present, diagnose affected DTC(s) first. If DTC(s) are not present, go to next step.
3. Turn ignition on. Using scan tool, select FAILURE REC under DTC mode and note ECT display. If the snapshot for ECT sensor reading is -35°F (-37°C) or less, go to next step. If snapshot ECT sensor reading is greater than -35°F (-37°C), go to step 5).
4. An intermittent high resistance reading occurred on the ECT sensor circuit. Check for open in ECT sensor ground and signal circuits. Repair as necessary. If circuits are okay, go to step 7).
5. If ECT snapshot reading is greater than 247°F (147°C), go to next step. If ECT snapshot reading is less than 247°F (147°C), go to step 7).
6. An intermittent low resistance reading occurred on the ECT sensor circuit. Check for short to ground in ECT sensor signal circuit. Repair as necessary. If circuits are okay, go to next step.
7. Allow engine to cool to less than 95°F (35°C). Start engine and raise ECT sensor temperature from cool to warm. As ECT sensor warms, watch ECT sensor reading on scan tool. Look for a skip or jump in the value. If a skip or jump is noted, go to next step. If value did not skip or jump, see DIAGNOSTIC AIDS.
8. Replace ECT sensor.

If fault is not present, perform On-Board Diagnostic (OBD) System Check.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, select ENGINE 1 and note ECT display. If temperature reading is 247°F (147°C) or greater, go to next step. If temperature reading is less than 247°F (147°C), fault is not present.
3. Disconnect ECT sensor harness connector. If temperature reading is 18°F (-28°C) or less, go to step 6). If temperature reading is greater than 18°F (-28°C), go to next step.
4. Store fluid life index as indicated on scan tool. Turn ignition on and wait 30 seconds, then disconnect PCM harness connector C2. Using DVOM, check resistance between ECT sensor signal circuit and ground. If resistance is 5 ohms or greater, go to step 8). If resistance is less than 5 ohms, go to next step.
5. Repair short to ground in ECT sensor signal circuit.
6. Check terminal contact at ECT sensor connector. Repair as necessary. If terminal contact is okay, go to next step.
7. Replace ECT sensor.
8. Check terminal contact of ECT sensor signal circuit at PCM connector C2. Repair as necessary. If terminal contact is okay, go to next step.
9. Replace PCM. Program replacement PCM using required equipment.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, select ENGINE 1 and note ECT display. If temperature reading is -36°F (-38°C) or less, go to next step. If temperature reading is greater than -36°F (-38°C), fault is not present.
3. Disconnect ECT sensor harness connector. Using jumper wire, jumper ECT sensor connector terminals together. If temperature reading is greater than 275°F (135°C), go to step 9). If temperature reading is 275°F (135°C) or less, go to next step.
4. Connect jumper from ECT sensor signal circuit to ground. If temperature reading is 275°F (135°C) or greater, go to step 6). If temperature reading is less than 275°F (135°C), go to next step.
5. Remove jumper wire. Store fluid life reading indicated in scan tool. Turn ignition off for 30 seconds then disconnect PCM harness connector. Using DVOM, check resistance of ECT sensor signal circuit between PCM connector and ECT sensor connector. If resistance is 5 ohms or less, go to step 11). If resistance is greater than 5 ohms, go to step 7).
6. Remove jumper wire. Store fluid life index indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM harness connector. Using DVOM, check resistance of sensor ground circuit between PCM harness connector and ECT sensor harness connector. If resistance is 5 ohms or less, go to step 11). If resistance is greater than 5 ohms, go to step 8).
7. Repair open in ECT sensor signal circuit.
8. Repair open in ECT sensor ground circuit.
9. Check terminal contact at ECT sensor. Repair as necessary. If terminal contact is okay, go to next step.
10. Replace ECT sensor.
11. Check ECT sensor ground and signal circuit terminal contact at PCM harness connector. Repair as necessary. If terminal contacts are okay, go to next step.
12. Replace PCM. Program replacement PCM using required equipment.

If fault is not present, perform Powertrain On-Board Diagnostic (OBD) System Check.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC P0300 is also present. If DTC P0300 is present, diagnose DTC P0300 first. If DTC P0300 is not present, go to next step.
3. If DTC P0121 or P0122 is present, diagnose affected DTC first. If DTCs are not present, go to next step.
4. Using scan tool, select FAILURE REC. under DTC mode. Note TP sensor display. If snapshot TP sensor reading is zero degrees or less, go to next step. If snapshot TP sensor reading is greater than zero degrees, go to step 8).
5. An intermittent low voltage reading occurred on the TP sensor circuit. Check for possible open or short to ground in TP sensor signal circuit or open in 5-volt reference circuit. Repair as necessary. If circuits are okay, go to next step.
6. Slowly depress accelerator from closed throttle to wide open throttle. Note TP sensor reading. Watch for a sudden skip or jump in TP sensor reading. If reading skips or jumps, go to next step. If reading does not skip or jump, fault is not present.
7. Check for binding or sticky throttle. Check for chaffed TP sensor wires. Repair as necessary. If repairs were not necessary, go to step 11).
8. If snapshot TP sensor reading is greater than 85 degrees, go to next step. If the snapshot of TP sensor reading is less than 85 degrees, go to step 6).
9. An intermittent high voltage reading occurred on the TP sensor circuit. Check for open in TP sensor ground circuit or short in TP sensor signal circuit. Repair as necessary. If circuits are okay, go to next step.
10. Slowly depress accelerator from closed throttle to wide open throttle. Note TP sensor reading. Watch for a sudden skip or jump in TP sensor reading. If reading skips or jumps, go to next step. If reading does not skip or jump, fault is not present.
11. Replace TP sensor.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, select FAILURE REC. under DTC mode and note DTC P0121 display. If snapshot TP sensor reading is greater than 85 degrees, diagnose using DTC P0123 test. If TP snapshot reading is less than 85 degrees, go to next step.
3. If snapshot TP sensor reading is less than -5 degrees, diagnose using DTC P0122 test. If snapshot TP sensor reading is greater than -5 degrees, go to next step.
4. Replace TP sensor.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, select ENGINE 1 and note TP display. If TP sensor reads .1 volt or less, go to next step. If TP sensor reads greater than .1 volt, fault is not present. See DIAGNOSTIC AIDS.
3. Disconnect TP sensor harness connector. Jumper TP sensor 5-volt reference circuit and TP sensor signal circuit at sensor harness connector. If TP sensor reads 4.5 volts or greater, go to step 13). If TP sensor reads less than 4.5 volts, go to next step.
4. Using DVOM, check voltage between jumper wire and ground. If voltage is less than .5 volt, go to next step. If voltage is greater than .5 volt, go to step 8).
5. Remove jumper wire. Check voltage between TP sensor 5-volt reference circuit and ground. If voltage is 4.5 volts or greater, go to step 9). If voltage is less than 4.5 volts, go to next step.
6. Store fluid life index as indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM harness connector C1. Using DVOM, check resistance between ground and TP sensor 5-volt reference circuit at PCM connector. If resistance is 10,000 ohms or greater, go to next step. If resistance is less than 10,000 ohms, go to step 12).
7. Check resistance on TP sensor 5-volt reference circuit between PCM connector C1 and TP sensor harness connector. If resistance is 5 ohms or less, go to step 15). If 5-volt reference circuit resistance is greater than 5 ohms, go to step 10).
8. Store fluid life information as indicated on scan tool. Turn ignition off for 30 seconds and then disconnect PCM harness connector C1. Using DVOM, check resistance between TP sensor signal ground circuit at PCM connector C1 and TP sensor signal circuit at TP sensor harness connector. If resistance is 5 ohms or less, go to step 15). If resistance is greater than 5 ohms, go to step 11).
9. Repair short to ground in TP sensor signal circuit.
10. Repair open in TP sensor 5-volt reference circuit.
11. Repair open in TP sensor signal circuit.
12. Repair short to ground in TP sensor signal circuit, including splice to EGR valve.
13. Check terminal contact at TP sensor connector.
14. Replace TP sensor.
15. Check terminal contact at PCM connector C1. Repair as necessary. If terminal contacts are okay, go to next step.
16. Replace PCM. Program replacement PCM using required equipment.

If no faults are found, check all PCM related ground connections.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, select ENGINE 1 and note TP display. If TP sensor reads 4.85 volts or greater, go to next step. If TP sensor reads less than 4.85 volts, fault it not present. See DIAGNOSTIC AIDS.
3. Disconnect TP sensor harness connector. If TP sensor reads .1 volt or greater, go to next step. If not, go to step 5).
4. Store fluid life information as indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM harness connector C1. Ignition on. Using DVOM, check voltage between ground and TP sensor signal circuit at PCM harness connector C1. If voltage is more than .5 volt, go to step 9). If voltage is .5 volt or less, go to step 12).
5. Using DVOM, check voltage at TP sensor 5-volt reference circuit to ground. If voltage is greater than 4.5 volts, go to step 7). If voltage is less than 4.5 volts, go to next step.
6. Check voltage between TP sensor 5-volt reference circuit and sensor ground at harness connector. If voltage reading is less than 4.5 volts, go to step 8). If voltage reading is not less than 4.5 volts, go to step 10).
7. Repair short to voltage in TP sensor 5-volt reference voltage circuit.
8. Repair open in TP sensor ground circuit.
9. Repair short to voltage in TP sensor signal circuit.
10. Check terminal contact at TP sensor. Repair as necessary. If terminal contact is okay, go to next step.
11. Replace TP sensor.
12. Check terminal contacts at PCM harness connector terminal C1. Repair as necessary. If terminal contacts are okay, go to next step.
13. Replace PCM. Program replacement PCM using required equipment.

If fault is not present, perform Powertrain On-Board Diagnostic (OBD) System Check. Also review FAILURE REC. data from scan tool to determine conditions under which and how long ago DTC set.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, select FAILURE REC. and note ECT display. If ECT sensor reads -35°F (-37°C) or less, diagnose using DTC P0117 test. If ECT sensor reads greater than -35°F (-37°C), go to next step.
3. Start and warm engine to normal operating temperature. Using scan tool, select DATA LIST, ENGINE 1 and note ECT display while engine is warming up. If ECT reading is erratic or skipping (rapid changing), go to step 6). If ECT reading is normal, go to next step.
4. After engine is fully warmed up (about 20 minutes), note ECT display. If ECT reading is less than 185°F (85°C), go to next step. If ECT reading is greater than 185°F (85°C), fault is not present. See DIAGNOSTIC AIDS.
5. Check ECT sensor ground and signal circuits for high resistance. Repair as necessary. If circuits are okay, repair cooling system.
6. Check terminal contact at ECT sensor. Repair as necessary. If terminal contact is okay, go to next step.
7. Replace ECT sensor.

If fault is not present, check for an intermittent cooling system problem.

PCM provides a .45 volt reference signal to the HO2S through the Bank 1 high signal circuit. When HO2S is cold, less than 392°F (200°C), the sensor signal voltage will be about .45 volt and PCM will keep the system in "open loop". When HO2S is warm, sensor will swing from rich to lean rapidly, at least one switch every 2 seconds, if PCM is in good control of air/fuel mixture.

If sensor stays at lean voltage for greater than 40 seconds during this test, DTC will set. DTC will also set when there is a sensor circuit fault giving a false lean indication or air/fuel ratio is actually lean due to a vacuum leak or fuel control system fault.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check if DTC P0134 is also present. If DTC P0134 is present, diagnose this DTC first. If DTC P0134 is not present, go to next step.
3. If DTC was set because vehicle ran out of fuel, clear DTC. If vehicle did not run out of fuel, go to next step.
4. Start and warm engine until coolant temperature is at least 185°F (85°C). Using scan tool, select ENGINE 1 and note bank 1, sensor 1 oxygen sensor voltage. If voltage remains at less than .3 volt for 30 seconds or greater, go to next step. If voltage does not remain at .3 volt or less for 30 seconds or greater, fault is not present. See DIAGNOSTIC AIDS.
5. Turn ignition off. Disconnect rear HO2S harness connector. Start engine. Using DVOM, check voltage between HO2S terminals "A" and "B". If voltage remains at less than .3 volt for 30 seconds or greater, diagnose using DTC P0133 test. If voltage does not remain at .3 volt or less for 30 seconds or greater, go to next step.
6. Store fluid life index as indicated in scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM connector C2. Using DVOM, check resistance to ground at rear HO2S harness connector terminal "B". If resistance is greater than 10,000 ohms, go to next step. If not, go to step 8).
7. Check resistance between rear HO2S harness connector terminals "A" and "B". If resistance is 5 ohms or less, go to step 9). If resistance is greater than 5 ohms, go to step 10).
8. Repair short to ground in rear H02S high signal circuit.
9. Repair rear HO2S high and low signal circuit shorted to each other.
10. Check terminal contact at PCM connector C2 HO2S high and low signal circuits. Repair as necessary. If terminal contacts are okay, go to next step.
11. Replace PCM. Program replacement PCM using required equipment. After repairs, go to next step.

Check snapshot data for front long and rear long term fuel trim values. If both banks were lean, check for a condition that would cause lean engine operation. If only the rear bank was lean, check for a condition that would cause only the rear bank to be lean, such as an intermittent short to ground in HO2S high signal circuit. Never solder HO2S wires.

DTC P0131 Schematic. Scheme 7

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check if DTC P0134 is also present, diagnose this DTC first. If DTC P0134 is not present, go to next step.
3. Start and warm engine until coolant temperature is at 185°F (85°C) or greater. Using scan tool, select ENGINE 1 and note oxygen sensor voltage. If voltage remains at .6 volt or greater for 30 seconds or greater, go to next step. If voltage drops to less than .6 volt after 30 seconds, fault is not present. See DIAGNOSTIC AIDS.
4. Turn engine off. Disconnect rear HO2S sensor harness connector. Start engine. Using DVOM, check voltage between sensor terminals "A" and "B". If voltage remains at greater than .6 volt for 30 seconds or greater, diagnose using DTC P0133 test. If voltage drops to less than .6 volt after 30 seconds, go to next step.
5. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness terminal C2. Turn ignition on. Voltage reading should be .1 volt. If reading is greater than .1 volt, go to next step. If reading is less than .1 volt, go to step 7).
6. Repair short to ground in HO2S high signal circuit.
7. Check terminal contact at PCM connector C2 to HO2S high and low signal circuits. Repair as necessary. If terminal contacts are okay, go to next step.
8. Replace PCM. Program replacement PCM using required equipment. After repairs, go to next step.

Check snapshot data for front and rear long term fuel trim values. If both banks were rich, check for a condition that would cause a rich engine operation. If only the rear bank was rich, check for a condition that would cause only the rear bank to be rich, such as an intermittent short to voltage in HO2S high signal circuit. Never solder HO2S wires.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. If you are referred here from another DTC, go to step 4). If not, go to next step.
3. If any other DTC(s) are present, diagnose affected DTC(s) first. If other DTC(s) are not present, go to next step.
4. Start and warm engine until coolant temperature reaches about 185°F (85°C) or greater. Using scan tool, select ENGINE 1 and note bank 1 sensor 1 voltage display. Increase engine speed to 1200-2000 RPM for about 2 minutes. After 2 minutes rear HO2S reading should swing rapidly within .3-.6 volt range. If voltage reading is within range, go to step 6). If voltage reading is out of range, go to next step.
5. With engine speed still at 1200-2000 RPM, note LOOP STATUS on scan tool. If system is in "closed loop", go to step 10). If system is not in "closed loop", go to step 9).
6. If HO2S voltage stays between .3 and .6 volt longer than the time is swings out of range, go to step 9). If not, go to next step.
7. Check terminal contact for HO2S high and low signal voltage at PCM connector C2. Repair as necessary. If terminal contacts are okay, go to next step.
8. Check terminal contact at rear oxygen sensor. Repair as necessary. If terminal contact is okay, go to next step.
9. Replace rear HO2S. Check for possible oxygen sensor contamination such as, leaded fuel, incorrect gasket sealer or over rich operation.
10. Check for possible causes of extended rich or lean operation. Repair as necessary.

Never solder oxygen sensor wires.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Start and warm engine until coolant temperature reaches about 185°F (85°C) or greater. Using scan tool, select ENGINE 1 and note bank 1 sensor 1 voltage display for 30 seconds. If voltage remains between .3 and .6 volt, go to next step. If voltage does not remain between .3 and .6 volt, go to step 6).
3. Turn ignition off. Disconnect rear HO2S harness connector. Start engine. Using DVOM, check voltage between HO2S harness connector terminals "A" and "B". If voltage remains between .3 and .6 volt, diagnose using DTC P0133 test. If voltage does not remain between .3 and .6 volt, go to next step.
4. Store fluid life index as indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM harness connector C2. Using DVOM, check resistance between HO2S high signal circuit at PCM connector and HO2S harness connector terminal "B". If resistance is 5 ohms or less, go to next step. If resistance is greater than 5 ohms, go to step 9).
5. Check resistance between PCM connector C2 HO2S low signal circuit and HO2S harness connector terminal "A". If resistance is 5 ohms or less, go to next step. If resistance is 5 ohms or greater, go to step 10).
6. Turn ignition on, with engine off. Check voltage between HO2S harness connector terminals "C" and "D". Voltage reading should be 10.5 volts. If voltage is greater than 10.5 volts, go to next step. If voltage is less than 10.5 volts, go to step 8).
7. Using a jumper wire, jumper HO2S harness connector terminals "C" and "D". Set DVOM to amp scale. Connect DVOM in series between HO2S terminals "D" to "D" (harness to sensor). DVOM should read 0.9-1.5 amps. If reading is as specified, go to step 14). If reading is not as specified, go to step 13).
8. Check voltage between oxygen sensor harness connector terminal "D" to ground. If reading is 10.5 volts or greater, go to step 11). If reading is less than 10.5 volts, go to next step.
9. Repair open in HO2S high signal circuit.
10. Repair open in HO2S low signal circuit.
11. Repair open in HO2S ground circuit.
12. Repair open or short to ground in HO2S ignition circuit.
13. Replace HO2S.
14. Check terminal contacts at PCM connector C2. Repair as necessary. If terminal contacts are okay, go to next step.
15. Replace PCM. Program replacement PCM using required equipment.

Never solder oxygen sensor wires.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. Disconnect rear oxygen sensor. Using DVOM, check voltage between sensor harness connector terminals "C" and "D". If voltage reading is greater than 10.5 volts, go to next step. If voltage reading is less than 10.5 volts, go to step 4).
3. Using jumper wire, jumper sensor connector terminal "C" to harness connector terminal "C". Set DVOM to amp scale. Connect DVOM in series with sensor terminal "D" to sensor harness connector terminal "D". If DVOM reads between 0.9-1.5 amps, go to step 5). If DVOM reads less than 0.9 amp or greater than 1.5 amps, go to next step.
4. Check voltage from harness connector terminal "D" to ground. If reading is 10.5 volts or greater, go to step 6). If reading is less than 10.5 volts, go to step 7).5) Using scan tool, select FREEZE FRAME data and operate vehicle under the same conditions which set the DTC. If DTC resets, diagnose using DTC P0133 test. If DTC does not reset, fault is not present. See DIAGNOSTIC AIDS.
5. Using scan tool, select FREEZE FRAME data and operate vehicle under the same conditions which set the DTC. If DTC resets, diagnose using DTC P0133 test. If DTC does not reset, fault is not present. See DIAGNOSTIC AIDS.
6. Repair open in HO2S ground circuit.
7. Repair open or short to ground in HO2S ignition signal circuit.
8. Replace HO2S.

An intermittent open in HO2S ignition signal circuit or ground circuit may cause DTC to set. A malfunctioning rear HO2S may also set DTC. Never solder oxygen sensor wires.

PCM provides a .45 volt reference signal to the HO2S through the Bank 1 high signal circuit. When HO2S is cold, less than 392°F (200°C), the sensor signal voltage will be about .45 volt and PCM will keep the system in "open loop". When HO2S is warm, sensor will swing from rich to lean rapidly, at least one switch every 2 seconds, if PCM is in good control of air/fuel mixture.

If sensor stays at lean voltage for greater than 40 seconds during this test, DTC will set. DTC will also set when there is a sensor circuit fault giving a false lean indication or air/fuel ratio is actually lean due to a vacuum leak or fuel control system fault.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check if DTC P0140 is also present. Diagnose this DTC first. If DTC P0140 is not present, go to next step.
3. Start and warm engine until coolant temperature is at least 185°F (85°C). Using scan tool, select ENGINE 1 and note bank 1, sensor 2 oxygen sensor voltage. If voltage remains at less than .3 volt for 30 seconds or greater, go to next step. If voltage does not remain at .3 volt or less for 30 seconds or greater, fault is not present. See DIAGNOSTIC AIDS.
4. Turn ignition off. Disconnect HO2S harness connector. Start engine. Using DVOM, check voltage between HO2S terminals "A" and "B". If voltage remains at less than .3 volt for 30 seconds or greater, diagnose using DTC P0139 test. If voltage does not remain at .3 volt or less for 30 seconds or greater, go to next step.
5. Store fluid life index as indicated in scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM connector C2. Using DVOM, check resistance to ground at HO2S harness connector terminal "B". If resistance is greater than 10,000 ohms, go to next step. If resistance is less than 10,000 ohms, go to step 7).
6. Check resistance between HO2S harness connector terminals "A" and "B". If resistance is 5 ohms or less, go to step 8). If resistance is greater than 5 ohms, go to step 9).
7. Repair short to ground in H02S high signal circuit.
8. Repair HO2S high and low signal circuit shorted to each other.
9. Check terminal contact at PCM connector C2 HO2S high and low signal circuits. Repair as necessary. If terminal contacts are okay, go to next step.
10. Replace PCM. Program replacement PCM using required equipment.

Check snapshot data for front long and rear long term fuel trim values. If both banks were lean, check for a condition that would cause lean engine operation. If only the rear bank was lean, check for a condition that would cause only the rear bank to be lean, such as an intermittent short to ground in HO2S high signal circuit. Never solder oxygen sensor wires.

DTC P0137 Schematic. Scheme 8

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check if DTC P0140 is also present. Diagnose this DTC first. If DTC P0140 is not present, go to next step.
3. Start and warm engine until coolant temperature is at 185°F (85°C) or greater. Using scan tool, select ENGINE 1 and note oxygen sensor voltage. If voltage remains at .6 volt or greater for 30 seconds or greater, go to next step. If voltage drops to less than .6 volt after 30 seconds, fault is not present. See DIAGNOSTIC AIDS.
4. Turn engine off. Disconnect HO2S sensor harness connector. Start engine. Using DVOM, check voltage between sensor terminals "A" and "B". If voltage remains at greater than .6 volt for 30 seconds or greater, diagnose using DTC P0139 test. If voltage drops to less than .6 volt after 30 seconds, go to next step.
5. Store fluid life index as indicated in scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM terminal C2. Turn ignition on. Voltage reading should be .1 volt. If reading is greater than .1 volt, go to next step. If reading is less than .1 volt, go to step 7).
6. Repair short to ground in HO2S high signal voltage.
7. Check terminal contact at PCM connector C2 to HO2S high and low signal circuits. Repair as necessary. If terminal contacts are okay, go to next step.
8. Replace PCM. Program replacement PCM using required equipment. After repairs, go to next step.

Check snapshot data for front long and rear long term fuel trim values. If both banks were rich, check for a condition that would cause a rich engine operation. If only the rear bank was rich, check for a condition that would cause only the rear bank to be rich, such as an intermittent short to voltage in HO2S high signal circuit. Never solder HO2S wires.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. If you are referred here from another DTC, go to step 4). If not, go to next step.
3. If any other DTC(s) are present, diagnose affected DTC(s) first. If other DTC(s) are not present, go to next step.
4. Start and warm engine until coolant temperature reaches about 185°F (85°C) or greater. Using scan tool, select ENGINE 1 and note bank 1 sensor 2 voltage display. Increase engine speed to 1200-2000 RPM for about 2 minutes. After 2 minutes HO2S reading should swing rapidly within .3-.6 volt. If voltage reading is within range, go to step 9). If voltage reading is out of range, go to next step.
5. If HO2S voltage stays between .3-.6 volt longer than the time is swings out of range, go to step 8). If not, go to next step.
6. Check terminal contact for HO2S high and low signal voltage at PCM connector C2. Repair as necessary. If terminal contacts are okay, go to next step.
7. Check terminal contact at oxygen sensor. Repair as necessary. If terminal contact is okay, go to next step.
8. Replace pre-converter HO2S. Check for possible oxygen sensor contamination such as, leaded fuel, incorrect gasket sealer or over rich operation.
9. Check for possible causes of extended rich or lean operation. Repair as necessary.

Never solder oxygen sensor wires.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Start and warm engine until coolant temperature reaches about 185°F (85°C) or greater. Using scan tool, select ENGINE 1 and note bank 1 sensor 2 voltage display for 30 seconds. If voltage remains between .3-.6 volt, go to next step. If voltage does not remain between .3-.6 volt, go to step 6).
3. Turn ignition off. Disconnect HO2S harness connector. Start engine. Using DVOM, check voltage between HO2S harness connector terminals "A" and "B". If voltage remains between .3-.6 volt, diagnose using DTC P0139 test. If voltage does not remain between .3-.6 volt, go to next step.
4. Store fluid life index as indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM connector C2. Using DVOM, check resistance between HO2S high signal circuit at PCM connector and HO2S harness connector terminal "B". If resistance is 5 ohms or less, go to next step. If resistance is greater than 5 ohms, go to step 9).
5. Check resistance between PCM connector C2 HO2S low signal circuit and HO2S harness connector terminal "A". If resistance is 5 ohms or less, go to next step. If resistance is 5 ohms or greater, go to step 10).
6. Turn ignition on, with engine off. Check voltage between HO2S harness connector terminals "C" and "D". If voltage is greater than 10.5 volts, go to next step. If voltage is less than 10.5 volts, go to step 8).
7. Using a jumper wire, jumper HO2S harness connector terminals "C" and "D". Set DVOM to amp scale. Connect DVOM in series between HO2S terminals "D" to "D" (harness to sensor). If reading is 0.9-1.5 amps, go to step 14). If reading is not as specified, go to step 13).
8. Check voltage between oxygen sensor harness connector terminal "D" to ground. If reading is 10.5 volts or greater, go to step 11). If reading is less than 10.5 volts, go to next step.
9. Repair open in HO2S high signal circuit.
10. Repair open in HO2S low signal circuit.
11. Repair open in HO2S ground circuit.
12. Repair open or short to ground in HO2S ignition circuit.
13. Replace HO2S.
14. Check terminal contacts at PCM connector C2. Repair as necessary. If terminal contacts are okay, go to next step.
15. Replace PCM. Program replacement PCM using required equipment. After repairs, go to next step.

Never solder oxygen sensor wires.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. Disconnect pre-converter oxygen sensor. Using DVOM, check voltage between sensor harness connector terminals "C" and "D". If reading is greater than 10.5 volts, go to next step. If reading is less than 10.5 volts, go to step 4).
3. Using jumper wire, jumper sensor connector terminal "C" to harness connector terminal "C". Set DVOM to amp scale. Connect DVOM in series with sensor connector terminal "D" to harness connector terminal "D". If DVOM reads 0.9-1.5 amps, go to step 5). If DVOM reads less than 0.9 amp or greater than 1.5 amps, go to next step.
4. Check voltage from harness connector terminal "D" to ground. If reading is 10.5 volts or greater, go to step 6). If reading is less than 10.5 volts, go to step 7).
5. Using scan tool, select FREEZE FRAME data and operate vehicle under the same conditions which set the DTC. If DTC resets, diagnose using DTC P0139 test. If DTC does not reset, fault is not present. See DIAGNOSTIC AIDS.
6. Repair open in HO2S ground circuit.
7. Repair open or short to ground in HO2S ignition signal circuit.
8. Replace HO2S.

An intermittent open in HO2S ignition signal circuit or ground circuit may cause DTC to set. A malfunctioning pre-converter HO2S may also set DTC. Never solder oxygen sensor wires.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check if DTC P0146 is also present. Diagnose DTC P0146 first, if present. If DTC P0146 is not present, go to next step.
3. Start and warm engine until coolant temperature is at least 185°F (85°C). Using scan tool, select ENGINE 1 and note bank 1, sensor 3 oxygen sensor voltage. If voltage remains at less than .5 volt for 30 seconds or greater, go to next step. If voltage does not remain at .5 volt or less for 30 seconds or greater, fault is not present. See DIAGNOSTIC AIDS.
4. Turn ignition off. Disconnect HO2S harness connector. Start engine. Using DVOM, check voltage between HO2S terminals "A" and "B". If voltage remains at less than .5 volt for 30 seconds or greater, diagnose using DTC P0139 test. If voltage does not remain at .5 volt or less for 30 seconds or greater, go to next step.
5. Store fluid life index as indicated in scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM connector C2. Using DVOM, check resistance to ground at HO2S harness connector terminal "B". If resistance is greater than 10,000 ohms, go to next step. If resistance is less than 10,000 ohms, go to step 7).
6. Check resistance between HO2S harness connector terminals "A" and "B". If resistance is 5 ohms or less, go to step 8). If resistance is greater than 5 ohms, go to step 9).
7. Repair short to ground in HO2S high signal circuit.
8. Repair HO2S high and low signal circuit shorted to each other.
9. Check terminal contact at PCM connector C2 HO2S high and low signal circuits. Repair as necessary. If terminal contacts are okay, go to next step.
10. Replace PCM. Program replacement PCM using required equipment.

Check snapshot data for front long and rear long term fuel trim values. If both banks were lean, check for a condition that would cause lean engine operation. If only the rear bank was lean, check for a condition that would cause only the rear bank to be lean, such as an intermittent short to ground in HO2S high signal circuit. Never solder oxygen sensor wires.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check if DTC P0146 is also present. Diagnose DTC P0146 first, if present. If DTC P0146 is not present, go to next step.
3. Start and warm engine until coolant temperature is at 185°F (85°C) or greater. Using scan tool, select ENGINE 1 and note oxygen sensor voltage. If voltage remains at .9 volt or greater for 30 seconds or greater, go to next step. If voltage does not remain at .9 volt or greater after 30 seconds, fault is not present. See DIAGNOSTIC AIDS.
4. Turn engine off. Disconnect HO2S sensor harness connector. Start engine. Using DVOM, check voltage between sensor terminals "A" and "B". If voltage remains at greater than .9 volt for 30 seconds or greater, go to step 7). If voltage does not remain at greater than .9 volt after 30 seconds, go to next step.
5. Store fluid life index as indicated in scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM terminal C2. Turn ignition on. Voltage reading should be .1 volt. If reading is greater than .1 volt, go to next step. If reading is less than .1 volt, go to step 8).
6. Repair short to ground in HO2S high signal voltage.
7. Replace post-converter HO2S.
8. Replace PCM. Program replacement PCM using required equipment.

Check snapshot data for front long and rear long term fuel trim values. If both banks were rich, check for a condition that would cause a rich engine operation. Never solder HO2S wires.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Start and warm engine until coolant temperature reaches about 185°F (85°C) or greater. Using scan tool, select ENGINE 1 and note bank 1 sensor 3 voltage display for 30 seconds. If voltage remains between .3-.6 volt, go to next step. If voltage does not remain between .3-.6 volt, go to step 6).
3. Turn ignition off. Disconnect post-converter HO2S harness connector. Start engine. Using DVOM, check voltage between HO2S harness connector terminals "A" and "B". If voltage remains between .3-.6 volt, diagnose using DTC P0139 test. If voltage does not remain between .3-.6 volt, go to next step.
4. Store fluid life index as indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM connector C2. Using DVOM, check resistance between HO2S high signal circuit at PCM connector and HO2S harness connector terminal "B". If resistance is 5 ohms or less, go to next step. If resistance is greater than 5 ohms, go to step 8).
5. Check resistance between PCM connector C2 HO2S low signal circuit and HO2S harness connector terminal "A". If resistance is 5 ohms or greater, go to step 13). If resistance is less than 5 ohms, go to step 9).
6. Turn ignition on, with engine off. Check voltage between HO2S harness connector terminals "C" and "D". If voltage is 10.5 volts or greater, go to step 12). If voltage is less than 10.5 volts, go to next step.
7. Check voltage between oxygen sensor harness connector terminal "D" to ground. If reading is 10.5 volts or greater, go to step 10). If reading is less than 10.5 volts, go to step 11).
8. Repair open in HO2S high signal circuit.
9. Repair open in HO2S low signal circuit.
10. Repair open in HO2S ground circuit.
11. Repair open or short to ground in HO2S ignition circuit.
12. Replace post-converter HO2S.
13. Check terminal contacts at PCM connector C2. Repair as necessary. If terminal contacts are okay, go to next step.
14. Replace PCM. Program replacement PCM using required equipment.

Never solder oxygen sensor wires.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. Disconnect post-converter oxygen sensor. Using DVOM, check voltage between sensor harness connector terminals "C" and "D". Voltage should be 10.5 volts. If reading is greater than 10.5 volts, go to next step. If reading is less than 10.5 volts, go to step 4).
3. Using jumper wire, jumper sensor connector terminal "D" to harness connector terminal "D". Set DVOM to amp scale. Connect DVOM in series with sensor connector terminal "C" to harness connector terminal "C". If DVOM reads between 0.9-1.5 amps, go to step 5). If DVOM reads less than 0.9 amp or greater than 1.5 amps, go to next step.
4. Check voltage from harness connector terminal "D" to ground. If reading is 10.5 volts or greater, go to step 6). If reading is less than 10.5 volts, go to step 7).
5. Using scan tool, select FREEZE FRAME data and operate vehicle under the same conditions which set the DTC. If DTC resets, diagnose using DTC P0139 test. If DTC does not reset, fault is not present. See DIAGNOSTIC AIDS.
6. Repair open in HO2S ground circuit.
7. Repair open or short to ground in HO2S ignition signal circuit.
8. Replace HO2S.

An intermittent open in HO2S ignition signal circuit or ground circuit may cause DTC to set. A malfunctioning pre-converter HO2S may also set DTC. Never solder oxygen sensor wires.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check if DTC P0154 is also present, diagnose this DTC first. If DTC P0154 is not present, go to next step.
3. If DTC was set because vehicle ran out of fuel, fault is not present. Clear DTC. If vehicle did not run out of fuel, go to next step.
4. Warm engine until coolant is at least 185°F (85°C). Using scan tool, note bank 2 sensor 1 voltage. If voltage remains less than .3 volt for 30 seconds or more, go to next step. If voltage does not remain less than .3 volt for 30 seconds or more, fault is not present. See DIAGNOSTIC AIDS.
5. Ignition off. Unplug HO2S connector. Start engine. Check voltage between HO2S terminals "A" and "B". If voltage remains less than .3 volt for 30 seconds or more, diagnose using DTC P0153 test. If voltage does not remain .3 volt or less for 30 seconds or more, go to next step.
6. Store fluid life index as indicated in scan tool. Turn ignition off and wait 30 seconds, disconnect PCM connector C2. Check resistance to ground at HO2S connector terminal "B". If resistance is greater than 10,000 ohms, go to next step. If less than 10,000 ohms, go to step 8).
7. Check resistance between HO2S harness connector terminals "A" and "B". If resistance is 5 ohms or less, go to step 9). If resistance is greater than 5 ohms, go to step 10).
8. Repair short to ground in HO2S high signal circuit.
9. Repair HO2S high and low signal circuit shorted to each other.
10. Check terminal contact at PCM connector C2 HO2S high and low signal circuits. Repair as necessary. If okay, go to next step.
11. Replace PCM. Program replacement PCM using required equipment.

Check snapshot data for front long and rear long term fuel trim values. If both banks were lean, check for a condition that would cause lean engine operation. If only the front bank was lean, check for a condition that would cause only the front bank to be lean, such as an intermittent short to ground in HO2S high signal circuit. Never solder oxygen sensor wires.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check if DTC P0154 is also present, diagnose this DTC first. If DTC P0154 is not present, go to next step.
3. Start and warm engine until coolant temperature is at 185°F (85°C) or greater. Using scan tool, note front oxygen sensor voltage. If voltage remains at .6 volt or greater for 30 seconds or more, go to next step. If voltage does not remain at .6 volt or greater after 30 seconds, fault is not present. See DIAGNOSTIC AIDS.
4. Turn engine off. Disconnect HO2S sensor harness connector. Start engine. Using DVOM, check voltage between sensor terminals "A" and "B". If voltage remains at greater than .6 volt for 30 seconds or more, go to step 7). If voltage does not remain at greater than .6 volt after 30 seconds, go to next step.
5. Store fluid life index as indicated in scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM terminal C2. Turn ignition on. If reading is greater than .1 volt, go to next step. If reading is less than .1 volt, go to step 8).
6. Repair short to ground in HO2S high signal voltage.
7. Replace post-converter HO2S.
8. Replace PCM. Program replacement PCM using required equipment.

Check snapshot data for front long and rear long term fuel trim values. If both banks were rich, check for a condition that would cause a rich engine operation. Never solder HO2S wires.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. If you are referred here from another DTC, go to step 4). If not, go to next step.
3. If any other DTC(s) are present, diagnose affected DTC(s) first. If other DTC(s) are not present, go to next step.
4. Start and warm engine until coolant temperature reaches about 185°F (85°C) or greater. Using scan tool, select note bank 2 sensor 1 voltage display. Increase engine speed to 1200-2000 RPM for about 2 minutes. After 2 minutes HO2S reading should swing rapidly within a range of .3-.6 volt. If voltage reading is within range, go to step 6). If voltage reading is out of range, go to next step.
5. With engine running at 1200-2000 RPM, note LOOP STATUS on scan tool. If scan tool indicates "closed loop", go to step 10). If scan tool does not indicate "closed loop", go to step 9).
6. If HO2S voltage stays between range of .3-.6 volt longer than the time is swings out of range, go to step 9). If not, go to next step.
7. Check terminal contact for HO2S high and low signal voltage at PCM connector C2. Repair as necessary. If terminal contacts are okay, go to next step.
8. Check terminal contact at oxygen sensor. Repair as necessary. If terminal contact is okay, go to next step.
9. Replace front HO2S. Check for possible sensor contamination such as, leaded fuel, incorrect gasket sealer or over rich operation.
10. Check for possible causes of extended rich or lean operation. Repair as necessary.

Never solder oxygen sensor wires.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Start and warm engine until coolant temperature reaches about 185°F (85°C) or greater. Using scan tool, monitor bank 2 sensor 1 voltage display for 30 seconds. If voltage remains between .3-.6 volt, go to next step. If voltage does not remain between .3-.6 volt, go to step 6).
3. Turn ignition off. Disconnect front HO2S harness connector. Start engine. Using DVOM, check voltage between HO2S harness connector terminals "A" and "B". If voltage remains between .3-.6 volt, diagnose using DTC P0153 test. If voltage does not remain between .3-.6 volt, go to next step.
4. Store fluid life index as indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM connector C2. Using DVOM, check resistance between HO2S high signal circuit at PCM connector and HO2S harness connector terminal "B". If resistance is 5 ohms or less, go to next step. If resistance is greater than 5 ohms, go to step 8).
5. Check resistance between PCM connector C2 HO2S low signal circuit and HO2S harness connector terminal "A". If resistance is greater than 5 ohms, go to step 10). If resistance is 5 ohms or less, go to next step.
6. Turn ignition on, with engine off. Check voltage between HO2S harness connector terminals "C" and "D". If voltage is greater than 10.5 volts, go to next step. If voltage is less than 10.5 volts, go to step 8).
7. Using jumper wire, jumper oxygen sensor terminal "D" to oxygen harness connector terminal "D". Set DVOM to amp scale. Install DVOM in series between oxygen sensor terminal "C" and harness connector terminal "D". If reading is 0.9-1.5 amps, go to step 14). If reading is not as specified, go to step 13).
8. Check voltage between oxygen sensor harness connector terminal "D" to ground. If reading is 10.5 volts or greater, go to step 11). If reading is less than 10.5 volts, go to step 12).
9. Repair open in HO2S high signal circuit.
10. Repair open in HO2S low signal circuit.
11. Repair open in HO2S ground circuit.
12. Repair open or short to ground in HO2S ignition circuit.
13. Replace front HO2S.
14. Check terminal contacts at PCM connector C2. Repair as necessary. If terminal contacts are okay, go to next step.
15. Replace PCM. Program replacement PCM using required equipment.

Never solder oxygen sensor wires.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. Disconnect front HO2S harness connector. Using DVOM, check voltage between HO2S harness connector terminals "C" and "D". If voltage reading is 10.5 volts or greater, go to next step. If voltage reading is less than 10.5 volts, go to step 4).
3. Using jumper wire, jumper oxygen sensor terminal "D" to oxygen harness connector terminal "D". Set DVOM to amp scale. Install DVOM in series between oxygen sensor terminal "C" and harness connector terminal "D". Turn ignition on. If reading is 0.9-1.5 amps, go to step 5). If reading is not as specified, go to step 8).
4. Check voltage from oxygen sensor harness connector terminal "D" to ground. If reading is 10.5 volts or greater, go to step 6). If reading is less than 10.5 volts, go to step 7).
5. Using scan tool, select FREEZE FRAME data and operate vehicle in the same conditions under which the DTC set. If DTC resets, diagnose using DTC P0153 test. If DTC does not reset, fault is not present. See DIAGNOSTIC AIDS.
6. Repair open in HO2S ground circuit.
7. Repair open or short in ignition circuit to HO2S.
8. Replace HO2S.

An intermittent open in ignition or ground circuits to HO2S may cause DTC P0155 to set. A malfunctioning oxygen sensor heater could also cause DTC to set. Never solder oxygen sensor wires.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check if any other DTC(s) are present. If other DTC(s) are present, diagnose affected DTC(s) first. If no other DTC(s) are present, go to next step.
3. Start an warm engine until coolant temperature reaches 185°F (85°C) or greater. Using scan tool, monitor LONG TERM BN. 1 and SHRT. TERM BN. 1 status. If either values are greater than 95-98 percent, go to next step. If either values are less than 95-98 percent, go to step 5).
4. Using FREEZE FRAME data, note conditions under which the was DTC set. Clear DTC and operate vehicle under the conditions that set DTC. Using scan tool, select NOT RUN SCC and TEST FAIL SCC to verify that this diagnostic test runs while duplicating test conditions. If this diagnostic test ran and failed this ignition cycle, go to next step. If this diagnostic test did not ran or did not fail in this ignition cycle, see DIAGNOSTIC AIDS.
5. If DTC P0174 is also present, go to next step. If DTC P0174 is not present, go to step 7).
6. Check vacuum hoses for splits, kinks and proper routing. Check throttle body, air induction system after MAF sensor, intake manifold, PCV and EGR valve for vacuum leaks. Check for contaminated fuel. Ensure PCM grounds are lean and tight. Check for mechanical failure. Repair as necessary. After repairs, go to step 8). If system is okay or no problem is found, see DIAGNOSTIC AIDS.
7. Inspect bank 1 for exhaust leaks, missing or loose exhaust hardware. Ensure HO2S is securely installed and wiring harness is not touching exhaust or ignition wires. Check for vacuum leaks that will only affect bank 1. Check for mechanical failure. If problem is found, go to next step. If system is okay or no problem is found, see DIAGNOSTIC AIDS.
8. Repair as necessary. After repairs, verify for proper operation of component(s).

If scan tool indicated that test ran and passed, fault is not present. If scan tool indicated that the test did not run, ensure that all the test conditions were met.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check if any other DTC(s) are present. If other DTC(s) are present, diagnose affected DTC(s) first. If no other DTC(s) are present, go to next step.
3. Start an warm engine until coolant temperature reaches 185°F (85°C) or greater. Using scan tool, monitor LONG TERM BN. 1 and SHRT. TERM BN. 1 status. If either values are less than -95 or -98 percent, go to next step. If either values are greater than -95 or -98 percent, go to step 5).
4. Using FREEZE FRAME data, note conditions under which the DTC was set. Clear DTC and operate vehicle under the conditions that set DTC. Using scan tool, select NOT RUN SCC and TEST FAIL SCC to verify that this diagnostic test runs while duplicating test conditions. If this diagnostic test ran and failed this ignition cycle, go to next step. If this diagnostic test did not run or did not fail in this ignition cycle, see DIAGNOSTIC AIDS.
5. If DTC P0175 is also present, go to next step. If DTC P0175 is not present, go to step 7).
6. Check for collapsed air intake duct, restricted air filter, improperly installed MAF sensor or for foreign objects blocking MAF sensor screen. Check for fuel in pressure regulator vacuum hose. If problem is found, go to step 8). If problem is not present, see DIAGNOSTIC AIDS.
7. Inspect for leaking injectors at bank 1. Repair as necessary. If injectors are okay, go to step 9).
8. Repair or replace any faulty items.
9. Replace rear HO2S.

If scan tool indicated that test ran and passed, fault is not present. If scan tool indicated that the test did not run, ensure that all the test conditions were met.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check if any other DTC(s) are present. If other DTC(s) are present, diagnose affected DTC(s) first. If no other DTC(s) are present, go to next step.
3. Start an warm engine until coolant temperature reaches 185°F (85°C) or greater. Using scan tool, monitor LONG TERM BN. 1 and SHRT. TERM BN. 1 status. If either values are greater than 95-98 percent, go to next step. If either values are less than 95-98 percent, go to step 5).
4. Using FREEZE FRAME data, note conditions under which the DTC set. Clear DTC and operate vehicle under the conditions that set DTC. Using scan tool, select NOT RUN SCC and TEST FAIL SCC to verify that this diagnostic test runs while duplicating test conditions. If this diagnostic test ran and failed this ignition cycle, go to next step. If this diagnostic test did not run or did not fail in this ignition cycle, see DIAGNOSTIC AIDS.
5. If DTC P0171 is also present, go to next step. If DTC P0171 is not present, go to step 7).
6. Check vacuum hoses for splits, kinks and proper routing. Check throttle body, air induction system after MAF sensor, intake manifold, PCV and EGR valve for vacuum leaks. Check for contaminated fuel. Ensure PCM grounds are lean and tight. Check for mechanical failure. Repair as necessary. After repairs, go to step 8). If system is okay or no problem is found, see DIAGNOSTIC AIDS.
7. Inspect bank 2 for exhaust leaks, missing or loose exhaust hardware. Ensure HO2S is securely installed and wiring harness is not touching exhaust or ignition wires. Check for vacuum leaks that will only affect bank 2. Check for mechanical failure. If problem is found, go to next step. If system is okay or no problem is found, see DIAGNOSTIC AIDS.
8. Repair as necessary. After repairs, verify for proper operation of component(s).

If scan tool indicated that test ran and passed, fault is not present. If scan tool indicated that the test did not run, ensure that all the test conditions were met.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check if any other DTC(s) are present. If other DTC(s) are present, diagnose affected DTC(s) first. If no other DTC(s) are present, go to next step.
3. Start an warm engine until coolant temperature reaches 185°F (85°C) or greater. Using scan tool, monitor LONG TERM BN. 1 and SHRT. TERM BN. 1 status. If either values are less than -95 or -98 percent, go to next step. If either values are greater than -95 or -98 percent, go to step 5).
4. Using FREEZE FRAME data, note conditions under which the DTC set. Clear DTC and operate vehicle under the conditions that set DTC. Using scan tool, select NOT RUN SCC and TEST FAIL SCC to verify that this diagnostic test runs while duplicating test conditions. If this diagnostic test ran and failed this ignition cycle, go to next step. If this diagnostic test did not ran or did not fail in this ignition cycle, see DIAGNOSTIC AIDS.
5. If DTC P0172 is also present, go to next step. If DTC P0172 is not present, go to step 7).
6. Check for collapsed air intake duct, restricted air filter, improperly installed MAF sensor or for foreign objects blocking MAF sensor screen. Check for fuel in pressure regulator vacuum hose. If problem is found, go to step 8). If problem is not present, see DIAGNOSTIC AIDS.
7. Inspect for leaking injectors at bank 1. Repair as necessary. If injectors are okay, go to step 9).
8. Repair or replace any faulty components.
9. Replace rear HO2S.

If scan tool indicated that test ran and passed, fault is not present. If scan tool indicated that the test did not run, ensure that all the test conditions were met.

The PCM contains a General Field Effect Transistor Driver (GFD) that controls the 8 fuel injector drivers. The GFD is used to determine if there is a problem with any of the fuel injector circuits. The GFD has a fault line for each injector. The fault line goes high when an open, short to ground, or short to voltage is noticed in an injector circuit. DTC will set when the fault line for an injector is high.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC(s) P0204, P0206 and P0207 are also present. If these DTC(s) are present, go to next step. If these DTC(s) are not present, go to step 7).
3. Turn ignition off. Remove and inspect INJ 2 fuse. If fuse is faulty, go to next step. If fuse is okay, go to 6).
4. Disconnect fuel rail harness connector. Using DVOM, check resistance between fuel rail harness connector terminal "N" and ground. If resistance is greater than 5 ohms, go to next step. If resistance is less than 5 ohms, go to step 17).
5. Disconnect injector No. 1 harness connector. Check resistance between injector No. 1 harness connector terminal "A" and ground. Repeat test to injectors No. 4, 6 and 7. If resistance is less than 5 ohms on any of the circuits, go to step 18). If resistance is greater than 5 ohms on any of the circuits, go to step 19).
6. Disconnect fuel rail harness connector. Replace INJ 2 fuse. Turn ignition on. Using DVOM, check voltage between fuel rail harness connector terminal "N" and ground. If reading is 10 volts or greater, go to step 20). If reading is less than 10 volts, go to step 21).
7. Using scan tool, select DTC INFO then LAST TST. FAIL mode. If this DTC failed its last test, go to step 9). If this DTC does not show that it failed its last test, go to next step.
8. Clear DTC(s) and operate vehicle until DTC P0201 resets. If DTC P0201 resets, go to next step. If DTC P0201 does not reset, fault is not present.
9. Turn ignition off. Disconnect injector No. 1 harness connector. Turn ignition on. Check voltage between injector No. 1 harness connector terminal "A" and ground. If reading is 10 volts or greater, go to next step. If reading is less than 10 volts, go to step 22).
10. Reconnect injector No. 1 harness connector. Store fluid life reading as indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Check voltage between PCM harness connector C2 terminal No. 9 and ground. If reading is less than 10 volts, go to next step. If not, go to step 14).
11. Disconnect injector No. 1 harness connector. Check resistance between injector terminals "A" and "B". If resistance is greater than 8 ohms, go to next step. If resistance is less than 8 ohms, go to step 27).
12. Check voltage between injector No. 1 harness connector terminal "A". If reading is .1 volt or less, go to next step. If reading is greater than .1 volt, go to step 23).
13. Check terminal contact at PCM connector C2. Repair as necessary. If terminal contact is okay, go to step 28).
14. Turn ignition off. Reconnect PCM connector C2. Disconnect fuel rail harness connector. Turn ignition on. Turn ignition on. Check voltage between injector harness terminal "A" and ground. DVOM should read 10 volts. If reading not as specified, go to next step. If reading is as specified, go to step 24).
15. Disconnect injector No. 1 harness connector. Check resistance between injector terminal "A" and ground. Resistance should be 10,000 ohms. If resistance is greater than 10,000 ohms, go to next step. If resistance is less than 10,000 ohms, go to step 25).
16. Check resistance between injector terminals "A" and "B". If resistance is greater than 25 ohms, go to step 27). If resistance is 25 ohms or less, go to step 26).
17. Repair short to ground between fuse and fuel rail connector.
18. Repair short to ground between fuel rail connector and injector connector that low resistance was measured on.
19. Replace INJ 2 fuse and retest for DTC(s).
20. Repair open in circuit between splice and duel rail connector.
21. Repair open in circuit between fuse B7 and fuel rail connector, or repair poor terminal contact at fuse.
22. Repair open in circuit between splice and injector No. 1.
23. Repair short to voltage between injector harness connector and PCM harness connector.
24. Repair open or short to ground in circuit between fuel rail connector and PCM.
25. Repair short to ground in circuit between fuel rail connector and injector No. 1.
26. Repair open in circuit between fuel rail connector and injector No. 1.
27. Replace fuel injector.
28. Replace PCM. Program replacement PCM using required equipment.

DTC P0201 Schematic. Scheme 9

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC(s) P0203, P0205 and P0208 are also present. If these DTC(s) are present, go to next step. If these DTC(s) are not present, go to step 7).
3. Turn ignition off. Remove and inspect INJ 1 fuse. If fuse is faulty, go to next step. If fuse is okay, go to step 6).
4. Disconnect fuel rail harness connector. Using DVOM, check resistance between fuel rail harness connector terminal "P" and ground. If resistance is greater than 5 ohms, go to next step. If resistance is less than 5 ohms, go to step 17).
5. Disconnect injector No. 2 harness connector. Check resistance between injector No. 2 harness connector terminal "A" and ground. Repeat test to injectors No. 3, 5 and 8. If resistance is less than 5 ohms on any of the circuits, go to step 18). If resistance is greater than 5 ohms on any of the circuits, go to step 19).
6. Disconnect fuel rail harness connector. Replace INJ 1 fuse. Turn ignition on. Using DVOM, check voltage between fuel rail harness connector terminal "P" and ground. If reading is 10 volts or greater, go to step 20). If reading is less than 10 volts, go to step 21).
7. Using scan tool, select DTC INFO then LAST TST. FAIL mode. If this DTC failed its last test, go to step 9). If this DTC does not show that it failed its last test, go to next step.
8. Clear DTC(s) and operate vehicle until DTC P0202 resets. If DTC P0202 resets, go to next step. If DTC P0202 does not reset, fault is not present.
9. Turn ignition off. Disconnect injector No. 2 harness connector. Turn ignition on. Check voltage between injector No. 2 harness connector terminal "A" and ground. If reading is 10 volts or greater, go to next step. If reading is less than 10 volts, go to step 22).
10. Reconnect injector No. 2 harness connector. Store fluid life reading as indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Check voltage between PCM harness connector C2 terminal No. 10 and ground. If voltage is less than 10 volts, go to next step. If not, go to step 14).
11. Disconnect injector No. 2 harness connector. Check resistance between injector terminals "A" and "B". If resistance is greater than 8 ohms, go to next step. If resistance is less than 8 ohms, go to step 27).
12. Check voltage between injector No. 2 harness connector terminal "B". If reading is .1 volt or less, go to next step. If reading is greater than .1 volt, go to step 23).
13. Check terminal contact at PCM connector C2. Repair as necessary. If terminal contact is okay, go to step 28).
14. Turn ignition off. Reconnect PCM connector C2. Disconnect fuel rail harness connector. Turn ignition on. Check voltage between injector harness terminal "A" and ground. Voltage should be 10 volts. If voltage not as specified, go to next step. If voltage is as specified, go to step 24).
15. Disconnect injector No. 2 harness connector. Check resistance between injector terminal "B" and ground. Resistance should be 10,000 ohms. If resistance is greater than 10,000 ohms, go to next step. If resistance is less than 10,000 ohms, go to step 25).
16. Check resistance between injector terminals "A" and "B". If resistance is greater than 25 ohms, go to step 27). If resistance is less than 25 ohms, go to step 26).
17. Repair short to ground between fuse and fuel rail connector.
18. Repair short to ground between fuel rail connector and injector connector that low resistance was measured on.
19. Replace fuse and retest for DTC(s).
20. Repair open in circuit between splice and fuel rail connector.
21. Repair open in circuit between fuse and fuel rail connector, or repair poor terminal contact at fuse.
22. Repair open in circuit between splice and injector No. 1.
23. Repair short to voltage between injector harness connector and PCM harness connector.
24. Repair open or short to ground in circuit between fuel rail connector and PCM.
25. Repair short to ground in circuit between fuel rail connector and injector No. 1.
26. Repair open in circuit between fuel rail connector and injector No. 1.
27. Replace fuel injector.
28. Replace PCM. Program replacement PCM using required equipment.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC(s) P0202, P0205 and P0208 are also present. If these DTC(s) are present, diagnose using DTC P0202 test. If these DTC(s) are not present, go to next step.
3. Using scan tool, select DTC INFO then LAST TST. FAIL mode. If this DTC failed its last test, go to step 5). If this DTC does not show that it failed its last test, go to next step.
4. Clear DTC(s) and operate vehicle until DTC P0203 resets. If DTC P0203 resets, go to next step. If DTC P0203 does not reset, fault is not present.
5. Turn ignition off. Disconnect injector No. 3 harness connector. Turn ignition on. Check voltage between injector No. 3 harness connector terminal "A" and ground. If reading is 10 volts or greater, go to next step. If reading is less than 10 volts, go to step 13).
6. Reconnect injector No. 3 harness connector. Store fluid life reading as indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Check voltage between PCM harness connector C2 terminal No. 12 and ground. If voltage is greater than 10 volts, go to next step. If voltage is less than 10 volts, go to step 10).
7. Disconnect injector No. 3 harness connector. Check resistance between injector terminals "A" and "B". If resistance is greater than 8 ohms, go to next step. If resistance is less than 8 ohms, go to step 18).
8. Check voltage between injector No. 3 harness connector terminal "B". If reading is .1 volt or less, go to next step. If reading is greater than .1 volt, go to step 14).
9. Check terminal contact at PCM connector C2. Repair as necessary. If terminal contact is okay, go to step 19).
10. Turn ignition off. Reconnect PCM connector C2. Disconnect fuel rail harness connector. Turn ignition on. Turn ignition on. Check voltage between injector harness terminal "D" and ground. If voltage is less than 10 volts, go to next step. If not, go to step 15).
11. Disconnect injector No. 3 harness connector. Check resistance between injector terminal "A" and ground. If resistance is greater than 10,000 ohms, go to next step. If resistance is less than 10,000 ohms, go to step 16).
12. Check resistance between injector terminals "A" and "B". If resistance is greater than 25 ohms, go to step 18). If resistance is less than 25 ohms, go to step 17).
13. Repair open in circuit between splice and injector No. 3.
14. Repair short to voltage between injector harness connector and PCM harness connector.
15. Repair open or short to ground in circuit between fuel rail connector and injector No. 3.
16. Repair short to ground in circuit between fuel rail connector and injector No. 3.
17. Repair open in circuit between fuel rail connector and injector No. 3.
18. Replace fuel injector.
19. Replace PCM. Program replacement PCM using required equipment.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC(s) P0201, P0206 and P0207 are also present. If these DTC(s) are present, diagnose using DTC P0201 test. If these DTC(s) are not present, go to next step.
3. Using scan tool, select DTC INFO then LAST TST. FAIL mode. If this DTC failed its last test, go to step 5). If this DTC does not show that it failed its last test, go to next step.
4. Clear DTC(s) and operate vehicle until DTC P0204 resets. If DTC P0204 resets, go to next step. If DTC P0204 does not reset, fault is not present.
5. Turn ignition off. Disconnect injector No. 4 harness connector. Turn ignition on. Check voltage between injector No. 4 harness connector terminal "A" and ground. If reading is 10 volts or greater, go to next step. If reading is less than 10 volts, go to step 13).
6. Reconnect injector No. 3 harness connector. Store fluid life reading as indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Check voltage between PCM harness connector C2 terminal No. 13 and ground. If voltage is greater than 10 volts, go to next step. If voltage is less than 10 volts, go to step 10).
7. Disconnect injector No. 4 harness connector. Check resistance between injector terminals "A" and "B". If resistance is greater than 8 ohms, go to next step. If resistance is less than 8 ohms, go to step 18).
8. Check voltage between injector No. 4 harness connector terminal "B". If reading is .1 volt or less, go to next step. If reading is greater than .1 volt, go to step 14).
9. Check terminal contact at PCM connector C2. Repair as necessary. If terminal contact is okay, go to step 19).
10. Turn ignition off. Reconnect PCM connector C2. Disconnect fuel rail harness connector. Turn ignition on. Turn ignition on. Check voltage between injector harness terminal "E" and ground. If voltage is less than 10 volts, go to next step. If not, go to step 15).
11. Disconnect injector No. 4 harness connector. Check resistance between injector terminal "A" and ground. If resistance is greater than 10,000 ohms, go to next step. If resistance is less than 10,000 ohms, go to step 16).
12. Check resistance between injector terminals "A" and "B". If resistance is greater than 25 ohms, go to step 18). If resistance is less than 25 ohms, go to step 17).
13. Repair open in circuit between splice and injector No. 4.
14. Repair short to voltage between injector harness connector and PCM harness connector.
15. Repair open or short to ground in circuit between fuel rail connector and injector No. 4.
16. Repair short to ground in circuit between fuel rail connector and injector No. 4.
17. Repair open in circuit between fuel rail connector and injector No. 4.
18. Replace fuel injector.
19. Replace PCM. Program replacement PCM using required equipment.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC(s) P0202, P0203 and P0208 are also present. If these DTC(s) are present, diagnose using DTC P0202 test. If these DTC(s) are not present, go to next step.
3. Using scan tool, select DTC INFO then LAST TST. FAIL mode. If this DTC failed its last test, go to step 5). If this DTC does not show that it failed its last test, go to next step.
4. Clear DTC(s) and operate vehicle until DTC P0205 resets. If DTC P0205 resets, go to next step. If DTC P0205 does not reset, fault is not present.
5. Turn ignition off. Disconnect injector No. 5 harness connector. Turn ignition on. Check voltage between injector No. 5 harness connector terminal "A" and ground. If voltage is 10 volts or greater, go to next step. If voltage is less than 10 volts, go to step 13).
6. Reconnect injector No. 5 harness connector. Store fluid life reading as indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Check voltage between PCM harness connector C2 terminal No. 17 and ground. If voltage is greater than 10 volts, go to next step. If voltage is less than 10 volts, go to step 10).
7. Disconnect injector No. 5 harness connector. Check resistance between injector terminals "A" and "B". If resistance is greater than 8 ohms, go to next step. If resistance is less than 8 ohms, go to step 18).
8. Check voltage between injector No. 5 harness connector terminal "B". Voltage reading should be .1 volt. If voltage is .1 volt or less, go to next step. If voltage is greater than .1 volt, go to step 14).
9. Check terminal contact at PCM connector C2. Repair as necessary. If terminal contact is okay, go to step 19).
10. Turn ignition off. Reconnect PCM connector C2. Disconnect fuel rail harness connector. Turn ignition on. Turn ignition on. Check voltage between injector harness terminal "T" and ground. If voltage is less than 10 volts, go to next step. If not, go to step 15).
11. Disconnect injector No. 5 harness connector. Check resistance between injector terminal "A" and ground. If resistance is greater than 10,000 ohms, go to next step. If resistance is less than 10,000 ohms, go to step 16).
12. Check resistance between injector terminals "A" and "B". If resistance is greater than 25 ohms, go to step 18). If resistance is less than 25 ohms, go to step 17).
13. Repair open in circuit between splice and injector No. 5.
14. Repair short to voltage between injector harness connector and PCM harness connector.
15. Repair open or short to ground in circuit between fuel rail connector and injector No. 5.
16. Repair short to ground in circuit between fuel rail connector and injector No. 5.
17. Repair open in circuit between fuel rail connector and injector No. 5.
18. Replace fuel injector.
19. Replace PCM. Program replacement PCM using required equipment.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC(s) P0201, P0204 and P0207 are also present. If these DTC(s) are present, diagnose using DTC P0201 test. If these DTC(s) are not present, go to next step.
3. Using scan tool, select DTC INFO then LAST TST. FAIL mode. If this DTC failed its last test, go to step 5). If this DTC does not show that it failed its last test, go to next step.
4. Clear DTC(s) and operate vehicle until DTC P0206 resets. If DTC P0206 resets, go to next step. If DTC P0206 does not reset, fault is not present.
5. Turn ignition off. Disconnect injector No. 6 harness connector. Turn ignition on. Check voltage between injector No. 6 harness connector terminal "A" and ground. If reading is 10 volts or greater, go to next step. If reading is less than 10 volts, go to step 13).
6. Reconnect injector No. 6 harness connector. Store fluid life reading as indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Check voltage between PCM harness connector C2 terminal No. 18 and ground. If voltage is greater than 10 volts, go to next step. If voltage is less than 10 volts, go to step 10).
7. Disconnect injector No. 6 harness connector. Check resistance between injector terminals "A" and "B". If resistance is greater than 8 ohms, go to next step. If resistance is less than 8 ohms, go to step 18).
8. Check voltage between injector No. 6 harness connector terminal "B". If voltage is .1 volt or less, go to next step. If voltage is greater than .1 volt, go to step 14).
9. Check terminal contact at PCM connector C2. Repair as necessary. If terminal contact is okay, go to step 19).
10. Turn ignition off. Reconnect PCM connector C2. Disconnect fuel rail harness connector. Turn ignition on. Turn ignition on. Check voltage between injector harness terminal "U" and ground. If voltage is less than 10 volts, go to next step. If voltage is as specified, go to step 15).
11. Disconnect injector No. 6 harness connector. Check resistance between injector terminal "A" and ground. If resistance is greater than 10,000 ohms, go to next step. If resistance is less than 10,000 ohms, go to step 16).
12. Check resistance between injector terminals "A" and "B". If resistance is greater than 25 ohms, go to step 18). If resistance is less than 25 ohms, go to step 17).
13. Repair open in circuit between splice and injector No. 6.
14. Repair short to voltage between injector harness connector and PCM harness connector.
15. Repair open or short to ground in circuit between fuel rail connector and injector No. 6.
16. Repair short to ground in circuit between fuel rail connector and injector No. 6.
17. Repair open in circuit between fuel rail connector and injector No. 6.
18. Replace fuel injector.
19. Replace PCM. Program replacement PCM using required equipment.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC(s) P0201, P0204 and P0206 are also present. If these DTC(s) are present, diagnose using DTC P0201 test. If these DTC(s) are not present, go to next step.
3. Using scan tool, select DTC INFO then LAST TST. FAIL mode. If this DTC failed its last test, go to step 5). If this DTC does not show that it failed its last test, go to next step.
4. Clear DTC(s) and operate vehicle until DTC P0207 resets. If DTC P0207 resets, go to next step. If DTC P0207 does not reset, fault is not present.
5. Turn ignition off. Disconnect injector No. 7 harness connector. Turn ignition on. Check voltage between injector No. 7 harness connector terminal "A" and ground. If reading is 10 volts or greater, go to next step. If reading is less than 10 volts, go to step 13).
6. Reconnect injector No. 7 harness connector. Store fluid life reading as indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Check voltage between PCM harness connector C2 terminal No. 11 and ground. If voltage is greater than 10 volts, go to next step. If voltage is less than 10 volts, go to step 10).
7. Disconnect injector No. 7 harness connector. Check resistance between injector terminals "A" and "B". If resistance is greater than 8 ohms, go to next step. If resistance is less than 8 ohms, go to step 18).
8. Check voltage between injector No. 7 harness connector terminal "B". If reading is .1 volt or less, go to next step. If reading is greater than .1 volt, go to step 14).
9. Check terminal contact at PCM connector C2. Repair as necessary. If terminal contact is okay, go to step 19).
10. Turn ignition off. Reconnect PCM connector C2. Disconnect fuel rail harness connector. Turn ignition on. Turn ignition on. Check voltage between injector harness terminal "C" and ground. If voltage is less than 10 volts, go to next step. If not, go to step 15).
11. Disconnect injector No. 7 harness connector. Check resistance between injector terminal "A" and ground. If resistance is greater than 10,000 ohms, go to next step. If resistance is less than 10,000 ohms, go to step 16).
12. Check resistance between injector terminals "A" and "B". If resistance is greater than 25 ohms, go to step 18). If resistance is less than 25 ohms, go to step 17).
13. Repair open in circuit between splice and injector No. 7.
14. Repair short to voltage between injector harness connector and PCM harness connector.
15. Repair open or short to ground in circuit between fuel rail connector and injector No. 7.
16. Repair short to ground in circuit between fuel rail connector and injector No. 7.
17. Repair open in circuit between fuel rail connector and injector No. 7.
18. Replace fuel injector.
19. Replace PCM. Program replacement PCM using required equipment.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC(s) P0202, P0203 and P0205 are also present. If these DTC(s) are present, diagnose using DTC P0202 test. If these DTC(s) are not present, go to next step.
3. Using scan tool, select DTC INFO then LAST TST. FAIL mode. If this DTC failed its last test, go to step 5). If this DTC does not show that it failed its last test, go to next step.
4. Clear DTC(s) and operate vehicle until DTC P0208 resets. If DTC P0208 resets, go to next step. If DTC P0208 does not reset, fault is not present.
5. Turn ignition off. Disconnect injector No. 8 harness connector. Turn ignition on. Check voltage between injector No. 8 harness connector terminal "A" and ground. If reading is 10 volts or greater, go to next step. If reading is less than 10 volts, go to step 13).
6. Reconnect injector No. 8 harness connector. Store fluid life reading as indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Check voltage between PCM harness connector C2 terminal No. 22 and ground. If voltage is greater than 10 volts, go to next step. If voltage is less than 10 volts, go to step 10).
7. Disconnect injector No. 8 harness connector. Check resistance between injector terminals "A" and "B". If resistance is greater than 8 ohms, go to next step. If resistance is less than 8 ohms, go to step 18).
8. Check voltage between injector No. 8 harness connector terminal "B". If reading is .1 volt or less, go to next step. If reading is greater than .1 volt, go to step 14).
9. Check terminal contact at PCM connector C2. Repair as necessary. If terminal contact is okay, go to step 19).
10. Turn ignition off. Reconnect PCM connector C2. Disconnect fuel rail harness connector. Turn ignition on. Turn ignition on. Check voltage between injector harness terminal "V" and ground. If voltage is less than 10 volts, go to next step. If voltage is as specified, go to step 15).
11. Disconnect injector No. 8 harness connector. Check resistance between injector terminal "A" and ground. If resistance is greater than 10,000 ohms, go to next step. If resistance is less than 10,000 ohms, go to step 16).
12. Check resistance between injector terminals "A" and "B". If resistance is greater than 25 ohms, go to step 18). If resistance is less than 25 ohms, go to step 17).
13. Repair open in circuit between splice and injector No. 8.
14. Repair short to voltage between injector harness connector and PCM harness connector.
15. Repair open or short to ground in circuit between fuel rail connector and injector No. 8.
16. Repair short to ground in circuit between fuel rail connector and injector No. 8.
17. Repair open in circuit between fuel rail connector and injector No. 8.
18. Replace fuel injector.
19. Replace PCM. Program replacement PCM using required equipment.

Fuel pump is powered by fuel pump relay. PCM energizes the fuel pump relay for 2 seconds at ignition on, to provide fuel pressure for starting. After the 2 second fuel pump prime, PCM will not power fuel pump until 4X reference pulses are received, indicating that the engine is cranking or running. PCM monitors voltage in the fuel pump feedback circuit to select fuel pump voltage supply faults. DTC will set when PCM sees the fuel pump is not energized (2 volts or less on feedback) with engine cranking or running.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition off. Turn ignition on for 5 seconds. After 5 seconds, attempt to start engine. If engine starts and runs, go to next step. If engine does not start or starts but dies, go to step 7).
3. Using scan tool, note DTC status condition. If DTC failed in this ignition cycle, go to next step. If DTC did not fail in this ignition cycle, fault is not present. See DIAGNOSTIC AIDS.
4. With engine still running, note FP. VOLT FEEDBACK on scan tool. If voltage is greater than 2 volts, go to step 25). If voltage is less than 2 volts, go to next step.
5. Store fluid life as indicated on scan tool. Turn ignition off and wait 30 seconds, then removed fuel pump relay. Disconnect PCM harness connector C1. Using DVOM, check resistance between fuel pump relay harness connector terminal No. 87 and fuel pump feedback circuit at PCM harness connector. If resistance is 5 ohms or less, go to step 25). If resistance is greater than 5 ohms, go to next step.
6. Repair open in circuit between PCM and splice or check for poor terminal contact at PCM connector C1.
7. Check fuel pump fuse, located in rear fuse block. If fuse is okay, go to next step. If fuse is faulty, go to step 18).
8. Remove fuel pump relay. Turn ignition on. Using DVOM, check voltage to ground at relay harness connector terminal No. 30. If voltage is 10 volts or greater, go to next step. If voltage is less than 10 volts, go to step 23).
9. Check voltage between fuel pump harness connector terminals No. 30 and No. 86. If voltage is 10 volts or greater, go to next step. If voltage is less than 10 volts, go to step 24).
10. Connect a jumper between fuel pump harness connector terminals No. 30 and 87. If fuel pump operates, go to next step. If fuel pump does not operate, go to step 15).
11. Turn ignition off. Connect DVOM between fuel pump relay harness connector terminals No. 85 and No. 86. Wait 10 seconds, then turn ignition on and check voltage reading within 2 seconds after turning on ignition. If voltage is 10 volts or greater, go to next step. If voltage is less than 10 volts, go to step 13).
12. Replace fuel pump relay.
13. Store fluid life as indicated on scan tool. Turn ignition off for 30 seconds, then disconnect PCM harness connector C2. Using DVOM, check resistance between fuel pump relay control circuit at PCM harness connector and relay harness connector terminal No. 85. If resistance is 5 ohms or less, go to step 25). If resistance is greater than 5 ohms, go to next step.
14. Repair open in circuit between PCM harness connector and relay harness connector.
15. Using scan tool, note FP. VOLT FEEDBACK reading. If reading is 10 volts or greater, go to next step. If reading is less than 10 volts, go to step 17).
16. Check for open in circuit between fuel pump and splice. Repair as necessary. If circuit is okay, go to step 22).
17. Check for open in circuit between fuel pump and splice.
18. Turn ignition off. Remove fuel pump relay. Using DVOM, check resistance between fuel pump harness connector terminal No. 30 and ground. If resistance is 2 ohms or greater, go to step 20). If resistance is less than 2 ohms, go to next step.
19. Repair short to ground between fuel pump fuse and relay.
20. Store fluid life as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM connector C1. Disconnect fuel pump connector. Check resistance to ground at fuel pump relay harness connector terminal No. 87. If resistance is greater than 2 ohms, go to step 22). If resistance is less than 20 ohms, go to next step.
21. Repair short to ground between PCM connector C1, fuel pump connector, fuel pump relay or a shorted fuel pump.
22. Check fuel pump ground circuit for cause of no-start condition. If ground circuit is okay, perform basic fuel pressure check.
23. Repair open in circuit between fuse and relay.
24. Repair open in ground circuit. If circuit is okay, check for poor ground connection.
25. Check terminal contact at PCM connector C1 fuel pump feedback circuit and PCM connector C2 fuel pump relay control circuit. Repair as necessary. If terminal contact is okay, go to next step.
26. Replace PCM. Program replacement PCM using required equipment.

If DTC sets without a driveability complaint, check for open circuit between splice and PCM or poor PCM terminal contact. If a complaint did not exist, check for poor relay contact, relay ground, etc.

DTC P0231 Schematic. Scheme 10

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on for 15 seconds. Using scan tool, note FP. VOLT FEEDBACK reading. If voltage is greater than 7 volts, go to next step. If voltage is less than 7 volts, fault is not present.
3. Remove fuel pump relay. If scan tool displays greater than 7 volts, go to next step. If voltage is less than 7 volts, go to step 6).
4. Store fluid life as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM connector C1. Turn ignition on. Check voltage to ground at PCM harness connector C1 fuel pump feedback circuit. If voltage is 7 volts or less, go to step 11). If voltage is greater than 7 volts, go to next step.
5. Check for loose or poor fuel pump ground connection. Repair as necessary. If ground connection is okay, go to step 8).
6. Turn ignition off. Wait 10 seconds. Using DVOM, check voltage between fuel pump relay harness connector terminals No. 85 and No. 86. Turn ignition on and note DVOM reading. If voltage reading remains at 12 volts for 10 seconds, go to next step. If voltage reading does not stay at 12 volts for 10 seconds, go to step 9).
7. Store fluid life as indicated on scan tool. Turn ignition off and wait 30 seconds. Disconnect PCM connector C2. Turn ignition on. Check voltage between ground and PCM harness connector fuel pump relay control circuit. If voltage is greater than zero volts, go to step 10). If voltage is zero volts, go to step 11).
8. Repair short to voltage in fuel pump feedback circuit.
9. Replace fuel pump.
10. Repair short to voltage in fuel pump relay control circuit.
11. Check terminal contact at PCM harness connector C1 fuel pump feedback circuit. Repair as necessary. If terminal contact is okay, go to next step.
12. Replace PCM. Program replacement PCM using required equipment.

DTC could set due to sluggish or intermittently stuck fuel pump relay.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check for any other DTC(s) present. If other DTC(s) are present, diagnose affected DTC(s) first. If other DTC(s) are not present, go to next step.
3. Start and idle engine. Using scan tool, observe MISFIRE CUR. counters in the misfire data list (there are 8 counters, one for each cylinder). If any of the counters are incrementing, go to next step. If counters are not incrementing, go to step 15).
4. Turn ignition off. Connect Spark Tester (ST-125) to ignition wire(s) that indicated a misfire. Ground the companion cylinder(s) plug wire. Start engine. If spark is present and consistent at spark tester, go to next step. If spark is not present or is intermittent at spark tester, go to step 9).
5. Turn ignition off. Remove and check spark plug from affected cylinder(s). If spark plug is okay (not oil or coolant fouled), diagnose fuel injector. See SYSTEM/COMPONENT TESTS article. If spark plug is fouled, go to next step.
6. If spark plug is oil or coolant fouled, check engine for mechanical problems. If spark plug is not fouled, go to next step.
7. If spark plug is cracked or improperly gapped, go to next step. If spark plug is okay, diagnose fuel injector(s). See SYSTEM/COMPONENT TESTS article.
8. Replace or re-gap spark plug.
9. Turn ignition off. Using DVOM, check resistance of each affected spark plug wire. If resistance is less than 15,000 ohms, go to next step. If resistance is greater than 15,000 ohms, go to step 13).
10. Remove affected coil(s). Check for carbon tracking on coil. If carbon tracking is not present, go to next step. If carbon tracking is present, go to step 12).
11. Switch position of coils at affected cylinder. Start and idle engine. If spark is present and consistent on spark tester, go to next step. If spark is not present or not consistent, go to step 14).
12. Turn ignition off. Replace faulty ignition coil and spark plug wire.
13. Replace spark plug wire.
14. Replace ignition control module.
15. Turn ignition on, with engine off. Review DTC P0300 snapshot data. Note conditions that the vehicle was operating when DTC was set and operate vehicle under the same condition. Using scan tool, observe MISFIRE CUR. counters in the misfire data list. If any of the counters are incrementing, repeat step 4). if counters are not incrementing, go to next step.
16. Turn ignition on, with engine off. Using scan tool, observe MISFIRE HIST. counters in the misfire data list. If more than 3 cylinders show a high misfire rate, go to step 18). If less than 3 cylinders show a high misfire rate, go to next step.
17. Note cylinder that shows a higher number of misfire. Check affected cylinder for damaged or high resistance spark plug wire, vacuum leak, damaged spark plug, etc. Repair as necessary. If no problems are found, see DIAGNOSTIC AIDS.
18. Check engine for proper vent operation, vacuum leaks or intermittent rich or lean condition. Repair as necessary. If not problems are found, see DIAGNOSTIC AIDS.

If more than one cylinder showed a history code of misfire, look for something in common between the cylinders such as, shared coils, etc. Also, check for vacuum leaks at the affected cylinder.

If fault cannot be duplicated, mist secondary ignition system with water and operate vehicle under conditions that set the DTC.

DTC P0300 Schematic. Scheme 11

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check if DTC P1376 is also present. If DTC P1376 is present, diagnose this DTC first. If DTC P1376 is not present, go to next step.
3. Start and idle engine. Using scan tool, select DTC INFO then FAIL THIS IGN. in DTC mode. If DTC P0322 is indicated as current, go to next step. If DTC P0322 does not indicate as current, go to step 9).
4. Store fluid life data as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM connector C2. Disconnect Ignition Control (IC) module harness connector C4. Using DVOM, check resistance between ground and IC module harness connector fuel control circuit terminal. If resistance is 10,000 ohms or greater, go to next step. If resistance is less than 10,000 ohms, go to step 9).
5. Check resistance between PCM harness connector fuel control circuit terminal and IC module harness connector C4 fuel control circuit terminal. If resistance is 5 ohms or less, go to next step. If resistance is 5 ohms or greater, go to step 13).
6. Turn ignition on. Check voltage to ground at IC module harness connector C4 fuel control circuit terminal. If voltage reading is .5 volt or less, go to next step. If voltage reading is greater than .5 volt, go to step 14).
7. Reconnect IC module harness connector C4. Check voltage to ground at PCM harness connector C4 cam signal circuit terminal. If voltage is 4.1 volts or greater, go to next step. If voltage is less than 4.1 volts, go to step 15).
8. Turn ignition off. Reconnect PCM harness connector C2. Using 6-Pin IC Module Diagnostic Jumpers, jumper the following IC module connector C4 terminals to the following module terminals: C4 Terminal "A" To Module Pin "A" C4 Terminal "B" To Module Pin "B" C4 Terminal "C" To Module Pin "C" C4 Terminal "D" To Module Pin "D" C4 Terminal "E" To Module Pin "E" C4 Terminal "F" To Module Pin "F" Set DVOM to amp scale. Connect DVOM between terminal "C" jumper. Start engine and check frequency in terminal "C" jumper. If frequency is 30-100 Hertz, go to step 16). If not 30-100 Hertz, go to step 15).
9. Using DVOM, check FAILURE REC. for DTC P0322 and note MAP value when DTC was set. If MAP value is greater than 80 kPa, go to next step. If MAP value is less than 80 kPa, go to step 11).
10. Check for intermittent short to voltage or for Electromagnetic Interference (EMI) on cam sensor wires. EMI can be caused by wiring being too close to spark plug wires or high power transmitters operating within vicinity. DTC can also be set by battery charger. Repair or correct problem as necessary. If circuits are okay and if the other conditions are not present, fault is not present.
11. Check for intermittent open or short in fuel control circuit between PCM and IC module connectors. Also check circuit to DIS fuse. Repair as necessary.
12. Repair short to ground in fuel control circuit.
13. Repair open in fuel control circuit.
14. Repair short to voltage in fuel control circuit.
15. Replace IC module.
16. Check terminal contact at fuel control circuit terminal at PCM harness connector. Repair as necessary. If terminal contact is okay, go to next step.
17. Replace PCM. Program replacement PCM using required equipment.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition off. Remove Knock Sensor (KS) module from PCM. Install a known-good KS module. Using FAILURE REC. snapshot data from scan tool, duplicate conditions when DTC originally set. Using scan tool, select DTC INFO then FAIL THIS IGN. function. If DTC P0325 resets, go to next step. If DTC P0325 does not reset, go to step 4).
3. Replace PCM. Program replacement PCM using required equipment.
4. Replace KS module.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Start engine. Observe if engine is producing excessive mechanical noise. If excessive noise is observed, go to next step. If excessive noise is not observed, go to step 4).
3. Locate and repair source of noise.
4. Use higher octane fuel. If higher octane fuel is not available, go to next step. If higher octane fuel is used, go to step 6).
5. Using scan tool, select MORE then select SERV. SPARK under MISC. TEST function. Activate SERV. SPARK (this can lower base timing from 10° to 6°BTDC). Retard base timing at 2°BTDC increments as needed. SERV. SPARK will stay at set reading until changed with scan tool or when power to PCM is disconnected.
6. Fill fuel tank with premium fuel. Drive vehicle for about 15 minutes, allowing PCM to adjust to the premium fuel.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Disconnect knock sensor/starter solenoid harness connector (on right side of engine compartment). Set DVOM to 400 mV AC scale. Check frequency (Hertz) at KS connector terminal. Tap on engine block with a non-metallic object. If frequency fluctuates while tapping block, go to step 5). If frequency does not fluctuate, go to next step.
3. Remove intake manifold. Disconnect knock sensor harness connector. Using DVOM, check frequency (Hertz) directly at knock sensor. Tap on engine block with a non-metallic object. If frequency fluctuates while tapping on block, go to next step. If frequency does not fluctuate, go to step 9).
4. Repair open or short to ground in circuit between knock sensor and knock sensor/starter solenoid harness connector.
5. Reconnect knock sensor/starter solenoid harness connector. Using scan tool, select STORE INFO. and save data stored when DTC was set. Store fluid life value as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Using DVOM, check frequency at PCM harness connector knock signal circuit, while tapping on engine block. If frequency fluctuates while tapping on block, go to step 7). If frequency does not fluctuate, go to next step.
6. Repair open or short to ground in circuit between PCM connector C2 and knock sensor/starter solenoid harness connector terminal.
7. Reconnect PCM connector. Using scan tool, select FAILURE REC. and note conditions under which the DTC set. Operate vehicle with engine temperature at about 104°F (40°C), TP sensor at 4.8 degrees, engine speed at 3000 RPM and ensure battery voltage is at least 11 volts. If DTC resets, go to next step. If DTC does not reset, fault is not present. See DIAGNOSTIC AIDS.
8. Check terminal contact at PCM connector C2 knock sensor signal circuit. Repair as necessary. If terminal contact is okay, go to step 11).
9. Check terminal contact at knock sensor. Repair as necessary. If terminal contact is okay, go to next step.
10. Replace knock sensor.
11. Replace PCM. Program replacement PCM using required equipment.

Check for an intermittent open or short in knock sensor circuit.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check if DTC P1376 is also present. If DTC P1376 is present, diagnose DTC first. If DTC P1376 is not present, go to next step.
3. Turn ignition off. Disconnect IC module connector C2. Using DVOM, check resistance between camshaft position sensor harness connector terminals. If resistance is 800-2100 ohms, go to next step. If resistance is not as specified, go to step 6).
4. Individually check resistance to ground at both IC module harness connector terminals. If resistance at either terminals is less than 100 ohms, go to step 12). If not, go to next step.
5. Disconnect IC module connector C3. Set DVOM to "peak min/max", 4-volt scale. Connect DVOM across camshaft position sensor harness connector terminals. Crank engine. If DVOM reads greater than .2 volt, go to step 9). If DVOM reads less than .2 volt, go to step 17).
6. If resistance is less than 800 ohms, go to next step. If resistance is greater than 800 ohms, go to step 8).
7. Disconnect camshaft position sensor connector. Check resistance between sensor harness connector terminals. If resistance is greater than 10,000 ohms, go to step 17). If resistance is less than 10,000 ohms, go to step 13).
8. Disconnect camshaft position sensor. Individually check continuity in sensor low and high signal voltage circuits. If continuity is present on both circuits, go to step 17). If continuity is not present on both or either circuits, go to step 14).
9. Reconnect IC module harness connector C2. Disconnect IC module harness connector C4. Using scan tool, store fluid life index as indicated. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Using DVOM, check resistance between ground camshaft position sensor signal circuit at PCM harness connector terminal. If resistance is less than 10,000 ohms, go to step 16). If resistance is greater than 10,000 ohms, go to next step.
10. Check resistance between camshaft position sensor signal circuit at PCM harness connector terminal. If resistance is 5 ohms or less, go to next step. If resistance is greater than 5 ohms, go to step 15).
11. Reconnect IC module connectors C3 and C4. Using DVOM, set DVOM to "peak min/max" 4-volt DC scale and push Hertz button. Connect DVOM between IC module harness connector terminal "B" (cam signal circuit) and ground. Crank engine. If frequency reading is greater than .4 Hertz, go to step 21). If frequency reading is less than .4 Hertz, go to step 19).
12. Repair short to ground in camshaft position sensor circuits between sensor and IC module harness connector.
13. Repair short between camshaft position sensor circuits.
14. Repair open or high resistance in camshaft position sensor circuits.
15. Repair open in cam signal circuit to PCM.
16. Repair short to ground in cam signal circuit to PCM.
17. Check terminal contact at camshaft position sensor terminal. Repair as necessary. If terminal contacts are okay, go to next step.
18. Replace camshaft position sensor.
19. Check terminal contact at IC module. Repair as necessary. If terminal contact is okay, go to next step.
20. Replace IC module.
21. Check terminal contact to cam signal circuit at PCM connector. Repair as necessary. If terminal contact is okay, go to next step.
22. Replace PCM. Program replacement PCM using required equipment.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Check for possible cause of Electromagnetic Interference (EMI), such as spark plug wires routed too close to IC module, high power transmitters operating within vicinity or the use of a battery charger. If possible source of EMI is found, remove source. If EMI interference is not noticed, go to next step.
3. Clear DTC(s) and retest. If DTC P0371 resets, go to next step. If DTC P0371 does not reset, fault is not present.
4. Check terminal contact of 24X spark reference circuit at IC module and PCM harness connector. Repair as necessary. If terminal contact is okay, go to next step.
5. Replace IC module.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, verify if DTC P1323 is also present. If DTC P1323 is present, diagnose this DTC first. If DTC P1323 is not present, go to next step.
3. Turn ignition off. Disconnect IC module harness connector C4. Using 6-Pin IC Module Diagnostic Jumpers, jumper the following IC module connector C4 terminals to the following module terminals: C4 Terminal "A" To Module Pin "A" C4 Terminal "B" To Module Pin "B" C4 Terminal "C" To Module Pin "C" C4 Terminal "D" To Module Pin "D" C4 Terminal "E" To Module Pin "E" C4 Terminal "F" To Module Pin "F" Set DVOM to 400 mV AC scale and push Hz button. Connect DVOM between terminal "A" jumper and ground. Start engine and check frequency. If frequency is 200 Hz or more, go to next step. If not, go to step 5).
4. Check terminal contact for 24X spark reference circuit at PCM connector C2. Check 24X reference circuit between PCM and IC module harness connectors. Repair as necessary. If terminal contact and circuit are okay, go to step 10).
5. Turn ignition on. Disconnect all jumpers. Turn ignition on. Using DVOM, check voltage between ground and cam low circuit terminal at IC module connector C4. If voltage is greater than 4.2 volts, go to next step. If voltage is less than 4.2 volts, go to step 8).
6. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Reconnect IC module harness connector C4. Turn ignition on. Using DVOM, check voltage between ground and 24X spark reference circuit at PCM harness connector C2. Voltage reading should be 4.2 volts. If voltage is greater than 4.2 volts, go to step 4). If voltage is less than 4.2 volts, go to next step.
7. Repair short to ground in 24X spark reference circuit.
8. Check terminal contact of cam signal circuit at IC module harness connector C4. Repair as necessary. If circuit is okay, go to next step.
9. Replace IC module.
10. Replace PCM. Program replacement PCM using required equipment.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. If fuel trim DTC(s) P0170, P0171, P0172, P0173, P0174 or P0175 are present, diagnose affected DTC(s) first. If these DTC(s) are not present, go to next step.
3. Ignition on, engine off. Check MAP sensor parameter on scan tool. If value is greater than 75 kPa (95 kPa at sea level), go to next step. If not greater than specification, go to step 9).
4. Unplug MAP sensor vacuum hose. Connect hand-held vacuum pump to MAP sensor. Apply 20 in. Hg to sensor. Each one in. of vacuum should result in a 3-4 kPa drop in MAP sensor reading. Change should be smooth. If a skip or jump occurs during application of vacuum, go to step 9). If no skip or jump occurs, go to next step.
5. With 20 in. Hg applied to sensor, if MAP reading is 34 kPa or less, go to next step. If not, go to step 9).
6. Remove vacuum source from MAP sensor. If MAP sensor parameter returns to original reading, go to next step. If not, go to step 9).
7. Reconnect MAP sensor vacuum hose. Start and idle engine. While monitoring MAP sensor value, command EGR from 0-70 percent in 10 percent increments. MAP sensor value should increase by about 4 kPa for each 10 percent increment. If MAP value does not increase accordingly and engine does not stall, go to next step. If MAP value increases accordingly or engine stalls, check EGR system for intermittent restrictions, blockages and/or leaks. If no fault is found, problem is intermittent.
8. Check EGR valve and all engine passages for restrictions and/or blockages. Repair as necessary. If no repairs are required, go to step 10).
9. Replace MAP sensor.
10. Replace EGR valve and verify problem is no longer present.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if other DTC(s) are present. If other DTC(s) are present, diagnose affected DTC(s) first. If other DTC(s) are not present, go to next step.
3. Check exhaust system for leaks, damage, loose or missing hardware. Repair as necessary. After repairs, go to step 5). If exhaust system is okay, go to next step.
4. Ensure original 3-way catalytic converter is installed. Check converter for damage or tamper. Ensure oxygen sensors are properly installed and wiring and connections are okay. Repair or replace components as necessary. After repairs, go to next step. If components are okay, go to step 6).
5. Using scan tool, select DTC INFO then DTC STATUS under DTC mode. Operate vehicle under which DTC was set. Observe scan tool display of DTC STATUS, looking for DTC to run or fail. If this DTC failed, go to next step. If this DTC did not fail, system is okay.
6. Replace catalytic converter.

Fuel with high sulfur content can cause a marginal converter to look bad. Check fuel quality.

This test determines if the Evaporative Emission (EVAP) control solenoid is open when the PCM is commanding it to open. PCM does this by monitoring EVAP vacuum switch which is a normally closed switch. Switch is located in vacuum line between EVAP canister and EVAP solenoid. When the switch opens, vacuum from the engine draws evaporative emissions from EVAP canister into throttle body.

The state of the EVAP switch is monitored by the PCM to determine if EVAP solenoid is open and passing vacuum. The PCM accomplishes this by monitoring the amount of time the EVAP switch is continuously open or closed during purge. The the test conditions are met, PCM starts a timer, which will be reset when the switch transitions open or closed or vice versa. If switch remains closed for 9 seconds continuously, DTC will set. If switch remains open for 2 seconds continuously, test is passed.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Check if DTC P1645 is also present. If DTC P1645 is present, diagnose DTC first. If DTC P1645 is not present, go to next step.
3. Start engine. Using scan tool, select EVAP VACUUM SW. Command EVAP solenoid on (100 percent). If scan tool reads PURGING, go to next step. If scan tool does not read PURGING, go to step 12).
4. Disconnect EVAP vacuum switch connector. If scan tool reads PURGING, go to next step. If scan tool does not read PURGING, go to step 12).
5. Reconnect EVAP switch connector. Disconnect EVAP vacuum switch vacuum hose (solenoid side) and install a "T" fitting between vacuum hose to solenoid. Connect a vacuum gauge to fitting. Start engine. Check vacuum with engine at idle and EVAP solenoid commanded on (100 percent). If vacuum reading is 4 in. Hg or greater, go to next step. If vacuum reading is less than 4 in. Hg, go to step 7).
6. Replace EVAP vacuum switch.
7. Disconnect EVAP control solenoid vacuum hose (intake manifold side). Connect vacuum gauge to hose and check vacuum with engine running. If vacuum reading is 4 in. Hg or greater, go to next step. If vacuum reading is less than 4 in. Hg, go to step 9).
8. Reconnect vacuum hose to EVAP control solenoid. Disconnect vacuum hose on other side (switch side) of EVAP control solenoid. Connect vacuum gauge on solenoid port. Check vacuum reading with engine running and EVAP control solenoid commanded on (100 percent). If vacuum reading is 4 in. Hg or greater, go to step 11). If vacuum reading is less than 4 in. Hg, go to step 10).
9. Repair blocked or leaking vacuum hose between intake manifold and EVAP control solenoid.
10. Replace EVAP control solenoid.
11. Check for vacuum leak in system between EVAP control solenoid and vapor canister, including switch. Repair as necessary. If vacuum leak is not present, go to step 13).
12. Repair short to ground in EVAP vacuum switch input circuit.
13. Replace vapor canister.

Never apply voltage to EVAP vacuum switch. Voltage supplied by PCM is of low current design. Switch damage could result if jumpered to voltage.

DTC P0441 Schematic. Scheme 12

This test determines if idle control system is maintaining the proper idle speed. The IAC system controls idle speed by allowing a certain amount of air to bypass the throttle body (throttle plate closed during idle) through the IAC valve. The PCM controlled IAC motor moves a pintle in and out of IAC valve, varying the amount of air entering the intake manifold. DTC will set when engine idle speed is less than 80 RPM or greater than the desired idle speed for 15 seconds.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check if other DTC(s) are present. If other DTC(s) are present, diagnose affected DTC(s) first. If other DTC(s) are not present, go to next step.
3. Start and idle engine. Turn off all accessories. Using scan tool, select MISC TESTS and select IAC SYSTEM. Command engine speed up to 1500 RPM, down to 500 RPM, then back to 1500 RPM while monitoring ENGINE SPEED display. If ENGINE SPEED display remains within 50 RPM of desired value for each RPM command, fault is not present. If engine speed is not within 50 RPM of desired value, go to next step.
4. Disconnect IAC valve. Install IAC Noid Light (J 37027). Start engine. Command engine speed up to 1500 RPM, down to 500 RPM, then back to 1500 RPM while monitoring noid light. If noid light cycles Red and Green (never off), go to step 6). If noid light does not cycle, go to next step.
5. Check all IAC circuits for open, short to ground or short to voltage. Repair as necessary. If circuits are okay, go to step 9).
6. Check throttle body for objects blocking IAC passage or throttle bore, excessive deposits in IAC passage, pintle, throttle bore or throttle plate. Check for restriction or vacuum leaks in air intake system. Check adjustment screw for tampering. Repair as necessary. If no problems are found, go to next step.
7. Check for poor terminal contact at IAC harness connector. Repair as necessary. If terminal contacts are okay, go to next step.
8. Replace IAC valve.
9. Check IAC terminal contacts at PCM harness connector C1. Repair as necessary. If terminal contacts are okay, go to next step.
10. Replace PCM. Program replacement PCM using required equipment.

DTC P0506 Schematic. Scheme 13

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check if other DTC(s) are present. If other DTC(s) are present, diagnose affected DTC(s) first. If other DTC(s) are not present, go to next step.
3. Start and idle engine. Turn off all accessories. Using scan tool, select MISC TESTS and select IAC SYSTEM. Command engine speed up to 1500 RPM, down to 500 RPM, then back to 1500 RPM while monitoring ENGINE SPEED display. If ENGINE SPEED display remains within 50 RPM of desired value for each RPM command, fault is not present. If engine speed is not within 50 RPM of desired value, go to next step.
4. Disconnect IAC valve. Install IAC Noid Light (J 37027). Start engine. Command engine speed up to 1500 RPM, down to 500 RPM, then back to 1500 RPM while monitoring noid light. If noid light cycles Red and Green (never off), go to step 6). If noid light does not cycle, go to next step.
5. Check all IAC circuits for open, short to ground or short to voltage. Repair as necessary. If circuits are okay, go to step 9).
6. Check throttle body for objects blocking IAC passage or throttle bore, excessive deposits in IAC passage, pintle, throttle bore or throttle plate. Check for restriction or vacuum leaks in air intake system. Check adjustment screw for tampering. Repair as necessary. If no problems are found, go to next step.
7. Check for poor terminal contact at IAC harness connector. Repair as necessary. If terminal contacts are okay, go to next step.
8. Replace IAC valve.
9. Check IAC terminal contacts at PCM harness connector C1. Repair as necessary. If terminal contacts are okay, go to next step.
10. Replace PCM. Program replacement PCM using required equipment.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, select PSP SWITCH. With engine running, turn steering wheel from straight ahead to full left lock position and back to straight ahead position. If scan tool displays NORMAL to HI PRESS. and back to NORMAL, fault is not present. See DIAGNOSTIC AIDS. If scan tool does not display NORMAL to HI PRESS. and back to NORMAL, go to next step.
3. Turn engine off. Turn ignition on, with engine off. If scan tool display remains on HI PRESS., go to next step. If scan tool display does not remain on HI PRESS., go to step 8).
4. Disconnect PSP switch. Using DVOM, check voltage between ground and PSP switch harness connector terminal "B". If voltage is 10 volts or greater, go to next step. If voltage is less than 10 volts, go to step 10).
5. Using jumper wire, jumper PSP switch harness connector terminals. If scan tool displays HI PRESS., go to next step. If scan tool does not display HI PRESS., go to step 11).
6. Store fluid life value as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. With PSP switch harness connector terminals jumpered, turn ignition on. Check voltage between ground and PSP switch input circuit at PCM harness connector terminal. If voltage reading is 10 volts or greater, go to next step. If voltage reading is less than 10 volts, go to step 12).
7. Check PSP switch input harness connector terminal at PCM connector C1. Repair as necessary. If harness connector terminals are okay, go to step 17).
8. Turn ignition on, with engine off. Disconnect PSP switch harness connector. If scan tool displays NORMAL, go to next step. If scan tool does not display NORMAL, got to step 11).
9. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Turn ignition on. Check voltage between ground and PSP switch input circuit at PCM harness connector C1. If voltage reading is .5 volt or less, go to step 7). If voltage reading is greater than .5 volt, go to step 13).
10. Check fuse. If fuse is faulty, go to step 14). If fuse is okay, go to step 15).
11. Check terminal contacts at PSP switch. Repair as necessary. If terminal contacts are okay, go to step 16).
12. Repair open or short in PSP switch input circuit between PCM harness connector and PSP switch harness connector.
13. Repair short to voltage in PSP switch input circuit between PCM harness connector and PSP switch harness connector.
14. Replace faulty fuse and check/repair short in ignition circuit to PSP switch.
15. Repair open in ignition circuit to PSP switch.
16. Replace PSP switch.
17. Replace PCM. Program replacement PCM using required equipment.

Check for intermittent contact at PSP switch or stretching of harness causing an intermittent open.

PCM monitors system voltage on ignition feed circuit to PCM harness connector C1. DTC will set if this voltage drops to less than 10 volts, with engine running at greater than 500 RPM. If ignition voltage is zero volts (open circuit), engine will not operate since PCM does not have the ignition feed voltage to operate.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Start engine. Using scan tool, note IGNITION 1 voltage reading. Compare this voltage to voltage displayed by the Instrument Panel Cluster (IPC) message center. Scan tool and IPC voltage difference should be within .5 volt. If difference is greater than .5 volt, go to next step. If scan tool and IPC voltage is within .5 volt, diagnose charging system. See DIAGNOSTIC AIDS.
3. Using DVOM, check voltage to ground on PCM fuse. Scan tool and DVOM voltage difference should be within .5 volt. If difference is greater than .5 volt, go to next step. If scan tool and DVOM voltage is within .5 volt or the same, diagnose charging system.
4. Check for high resistance in ignition feed circuit to PCM. Repair circuit as necessary. If circuit is okay, go to next step.
5. Check terminal contact PCM harness connectors C1 and C2. Repair as necessary. If terminal contacts are okay, go to next step.
6. Replace PCM. Program replacement PCM using required equipment.

Normal running system voltage is about 15 volts. A loose or faulty connection at generator "L" terminal may cause DTC to set intermittently.

DTC P0560 Schematic. Scheme 14

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Start engine. Using scan tool, note IGNITION 1 voltage reading. Compare this voltage to voltage displayed by the Instrument Panel Cluster (IPC) message center. If difference is greater than .5 volt, go to next step. If scan tool and IPC voltage is within .5 volt or the same, diagnose charging system. See DIAGNOSTIC AIDS.
3. Using DVOM, check voltage to ground on PCM fuse. If difference is greater than .5 volt, go to next step. If scan tool and DVOM voltage is the same or within .5 volt, diagnose charging system.
4. Check for high resistance in ignition feed circuit to PCM. Repair circuit as necessary. If circuit is okay, go to next step.
5. Check terminal contact PCM harness connectors C1 and C2. Repair as necessary. If terminal contacts are okay, go to next step.
6. Replace PCM. Program replacement PCM using required equipment.

Normal running system voltage is about 15 volts. A loose or faulty connection at generator "L" terminal may cause DTC to set intermittently.

The PCM EPROM contains data essential in running engine and transaxle. This test check the integrity of the data. The EPROM data is divided into 2 halves or sides in the EPROM. The integrity of the data is checked by adding up the data in all locations of the EPROM. This is called the checksum. If checksum does not equal to what it should, DTC will set.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Replace PCM. Program replacement PCM using required equipment.

DTC is designed not to allow a service/replacement PCM to be installed without first flashing software into it.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Flash PCM with correct software. Check if DTC resets. If DTC resets, go to next step.
3. Replace PCM. Program replacement PCM using required equipment.

The PCM has a memory area where it stores certain data it needs to save when the ignition is turned off. This area is called Keep Alive Memory. This test monitors PCM's keep alive memory for a loss or unintended change of data. If such a condition occurs, DTC will set.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check for other DTC(s) set. If other DTC(s) are set, diagnose affected DTC(s). If other DTC(s) are not present, see DIAGNOSTIC AIDS.

If battery has been disconnected for any reason, DTC P0603 will set. The PCM keeps a running check on the memory and if it changes, memory will reset. An intermittent loss of power or ground to PCM will cause a reset.

PCM has 2 internal processors, the ECM and the TCM. They are connected together and share data on an interconnect called SPI. The ECM sends sensor data to TCM. This sensor data is checked and if the difference in readings between the 2 processors is too great, DTC will set.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Replace PCM. Program replacement PCM using required equipment.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, verify if DTC P0106 or P0108 is also present. If these DTC(s) are present, diagnose affected DTC(s) first. If these DTC(s) are not present, go to next step.
3. Turn ignition off. Disconnect harness connector to MAP sensor. Check harness connector terminals. Repair as necessary. If terminals are okay, go to next step.
4. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Check MAP sensor terminals at PCM harness connector. Repair as necessary. If terminals are okay, go to step 5).
5. Disconnect MAP sensor connector. Check all sensor terminals. Repair as necessary. If terminals are okay, go to next step.
6. Check MAP sensor 5-volt reference and signal circuits for intermittent short to voltage. Also, check for open MAP sensor ground circuit. Repair as necessary. If circuits are okay, fault is not present. Diagnose using DTC P0106 test.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, verify if DTC P0106 or P0107 is also present. If these DTC(s) are present, diagnose affected DTC(s) first. If these DTC(s) are not present, go to next step.
3. Turn ignition off. Disconnect harness connector to MAP sensor. Check harness connector terminals. Repair as necessary. If terminals are okay, go to next step.
4. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Check MAP sensor terminals at PCM harness connector. Repair as necessary. If terminals are okay, go to step 5).
5. Disconnect MAP sensor connector. Check all sensor terminals. Repair as necessary. If terminals are okay, go to next step.
6. Check MAP sensor 5-volt reference and signal circuits for intermittent short to voltage. Also, check for open MAP sensor ground circuit. Repair as necessary. If circuits are okay, fault is not present. Diagnose using DTC P0106 test.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Start and idle engine. Using scan tool, note MAP and BARO displays. Subtract MAP value from BARO value. If difference is 11 kPa or less, go to next step. If difference is greater than 11 kPa, fault is not present. See DTC P0106 diagnosis.
3. Connect vacuum gauge at MAP sensor port. With engine at idle, if vacuum is 14 in. Hg or greater, go to next step. If vacuum is less than 14 in. Hg, go to step 9).
4. Turn engine off. Disconnect MAP sensor harness connector. Turn ignition on, with engine off. Note MAP display on scan tool. If MAP sensor display reads 16 kPa or less, go to next step. If MAP sensor display reads greater than 16 kPa, go to step 6).
5. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Using DVOM, check MAP sensor ground circuit resistance PCM harness connector and MAP sensor harness connector terminals. If resistance is 5 ohms or less, go to step 10). If resistance is greater than 5 ohms, go to next step.
6. Check voltage to ground at MAP sensor signal circuit harness connector terminal. If voltage is greater than .5 volt, go to step 8). If voltage is less than .5 volt, go to step 12).
7. Repair open in MAP sensor ground circuit.
8. Repair short to voltage in MAP sensor signal circuit or MAP sensor signal circuit and 5-volt reference signal circuit shorted together.
9. Check and repair cause of intake manifold vacuum leak or low engine vacuum. Repair as necessary.
10. Check terminal contact at MAP sensor. Repair as necessary. If terminal contact is okay, go to next step.
11. Replace MAP sensor.
12. Check terminal contacts to MAP sensor at PCM connector C1. Repair as necessary. If terminal contacts are okay, go to next step.
13. Replace PCM. Program replacement PCM using required equipment.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC P0111 or P0113 is also present. If either DTC is present, diagnose affected DTC first. If these DTC(s) are not present, go to next step.
3. Store fluid life index as indicated on scan tool. Turn ignition on and wait 30 seconds, then disconnect PCM harness connectors C1 and C2. Check terminals to IAT sensor at PCM harness connectors C1 and C2. Repair as necessary. If terminal contacts are okay, go to next step.
4. Disconnect and check IAT sensor harness connector. Repair as necessary. If terminal contacts are okay, go to next step.
5. Check IAT sensor signal and ground circuits for open or short to voltage between IAT sensor harness connector and PCM harness connector. Repair as necessary. If circuits are okay, fault is not present. See DIAGNOSTIC AIDS.

If fault is not present, check PCM grounds. If a faulty sensor is suspected, check sensor resistance. See IAT TEMPERATURE-TO-RESISTANCE VALUES.

IAT TEMPERATURE-TO-RESISTANCE VALUES

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC P0111 or P0112 is also present. If either DTC is present, diagnose affected DTC first. If these DTC(s) are not present, go to next step.
3. Store fluid life index as indicated on scan tool. Turn ignition on and wait 30 seconds, then disconnect PCM harness connectors C1 and C2. Check terminals to IAT sensor at PCM harness connectors C1 and C2. Repair as necessary. If terminal contacts are okay, go to next step.
4. Disconnect and check IAT sensor harness connector. Repair as necessary. If terminal contacts are okay, go to next step.
5. Check IAT sensor signal circuit for short to ground. Repair as necessary. If circuit is okay, fault is not present. See DIAGNOSTIC AIDS.

If fault is not present, check PCM grounds. If a faulty sensor is suspected, check sensor resistance. See IAT TEMPERATURE-TO-RESISTANCE VALUES.

IAT TEMPERATURE-TO-RESISTANCE VALUES

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC P0116 or P0117 is also present. If either DTC is present, diagnose affected DTC first. If these DTC(s) are not present, go to next step.
3. Store fluid life index as indicated on scan tool. Turn ignition on and wait 30 seconds, then disconnect PCM harness connectors C1 and C2. Check terminals to ECT sensor at PCM harness connectors C1 and C2. Repair as necessary. If terminal contacts are okay, go to next step.
4. Disconnect and check ECT sensor harness connector. Repair as necessary. If terminal contacts are okay, go to next step.
5. Check ECT sensor signal circuit for short to ground. Repair as necessary. If circuit is okay, fault is not present. See DIAGNOSTIC AIDS.

If fault is not present, check PCM grounds. If a faulty sensor is suspected, check for skewed ECT sensor. See ECT TEMPERATURE-TO-RESISTANCE VALUES table.

ECT TEMPERATURE-TO-RESISTANCE VALUES

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC P0116 or P0118 is also present. If either DTC is present, diagnose affected DTC first. If these DTC(s) are not present, go to next step.
3. Store fluid life index as indicated on scan tool. Turn ignition on and wait 30 seconds, then disconnect PCM harness connectors C1 and C2. Check terminals to ECT sensor at PCM harness connectors C1 and C2. Repair as necessary. If terminal contacts are okay, go to next step.
4. Disconnect and check ECT sensor harness connector. Repair as necessary. If terminal contacts are okay, go to next step.
5. Check ECT sensor signal and ground circuits for open or short to voltage. Repair as necessary. If circuit is okay, fault is not present. See DIAGNOSTIC AIDS.

If fault is not present, check PCM grounds. Check for skewed ECT sensor. See ECT TEMPERATURE-TO-RESISTANCE VALUES table.

ECT TEMPERATURE-TO-RESISTANCE VALUES

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC P0120 or P0123 is also present. If either DTC is present, diagnose affected DTC first. If these DTC(s) are not present, go to next step.
3. Store fluid life index as indicated on scan tool. Turn ignition on and wait 30 seconds, then disconnect PCM harness connector C1. Check terminals to TP sensor at PCM harness connector C1. Repair as necessary. If terminal contacts are okay, go to next step.
4. Disconnect and check TP sensor harness connector. Repair as necessary. If terminal contacts are okay, go to next step.
5. Check for open in TP sensor ground circuit. Check for short to voltage in TP sensor 5-volt reference and signal circuits. Repair as necessary. If circuits are okay, fault is not present. See DIAGNOSTIC AIDS.

If fault is not present, check PCM grounds.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC P0120 or P0123 is also present. If either DTC is present, diagnose affected DTC first. If these DTC(s) are not present, go to next step.
3. Store fluid life index as indicated on scan tool. Turn ignition on and wait 30 seconds, then disconnect PCM harness connector C1. Check terminals to TP sensor at PCM harness connector C1. Repair as necessary. If terminal contacts are okay, go to next step.
4. Disconnect and check TP sensor harness connector. Repair as necessary. If terminal contacts are okay, go to next step.
5. Check for open or short to ground in TP sensor 5-volt reference and signal circuits. Repair as necessary. If circuits are okay, fault is not present. See DIAGNOSTIC AIDS.

If fault is not present, check PCM grounds.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. If you were sent here from another DTC, go to step 4). If not, go to next step.
3. Using scan tool, check if other DTC(s) are present. If other DTC(s) are present, diagnose affected DTC(s) first. If no other DTC(s) are present, go to next step.
4. Start engine. Using scan tool, select ENGINE 1 and observe ECT display. Operate engine until temperature reaches 185°F (85°C). Note ENGINE SPEED and BNK 1 SEN 1 display. Operate engine at 1200-2000 RPM for about 2 minutes. After 2 minutes check if rear oxygen sensor voltage rapidly swings from less than .3 volt to greater than .6 volt. If oxygen sensor voltage is swinging as specified, go to next step. If oxygen sensor voltage is not swinging as specified, go to step 6).
5. With engine running at 1200-2000 RPM, note scan tool display LOOP STATUS. If display indicates CLOSED, fault is not present. See DIAGNOSTIC AIDS. If display does not indicate CLOSED, go to step 9).
6. If rear oxygen sensor voltage remains between .3-.6 volt longer that it swings out of this range, go to step 9). If oxygen sensor voltage swings, go to next step.
7. Check terminal contact at PCM harness connector C2. Repair as necessary. If terminal contact is okay, go to next step.
8. Check terminal contact at rear oxygen sensor connector. Repair as necessary. If harness connector is okay, go to next step.
9. Replace rear oxygen sensor. Check for possible sensor contamination, i.e. leaded fuel, incorrect gasket seal or over rich operation. If failure is caused by over rich condition, check fuel injection system. See BASIC TESTING article.

If fault is not present, check PCM grounds. Never solder oxygen sensor wires.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check if other DTC(s) are present. If other DTC(s) are present, diagnose affected DTC(s) first. If no other DTC(s) are present, go to next step.
3. Start engine. Using scan tool, select ENGINE 1 and observe ECT display. Operate engine until temperature reaches 185°F (85°C). Note ENGINE SPEED and BNK 1 SEN 1 display. Operate engine at 1200-2000 RPM for about 2 minutes. After 2 minutes check if rear oxygen sensor voltage rapidly swings from less than .3 volt to greater than .6 volt. If oxygen sensor voltage is swinging as specified, go to next step. If oxygen sensor voltage is not swinging as specified, go to step 5).
4. With engine running at 1200-2000 RPM, note scan tool display LOOP STATUS. If display indicates CLOSED, fault is not present. See DIAGNOSTIC AIDS. If display does not indicate CLOSED, go to step 8).
5. If rear oxygen sensor voltage remains between .3-.6 volt longer that it swings out of this range, go to step 8). If oxygen sensor voltage swings, go to next step.
6. Check terminal contact at PCM harness connector C2. Repair as necessary. If terminal contact is okay, go to next step.
7. Check terminal contact at rear oxygen sensor connector. Repair as necessary. If harness connector is okay, go to next step.
8. Replace rear oxygen sensor. Check for possible sensor contamination, i.e. leaded fuel, incorrect gasket seal or over rich operation. If failure is caused by over rich condition, check fuel injection system. See BASIC TESTING article.

If fault is not present, check PCM grounds. Never solder oxygen sensor wires.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. If you were sent here from another DTC, go to step 4). If not, go to next step.
3. Using scan tool, check if other DTC(s) are present. If other DTC(s) are present, diagnose affected DTC(s) first. If no other DTC(s) are present, go to next step.
4. Start engine. Using scan tool, select ENGINE 1 and observe ECT display. Operate engine until temperature reaches 185°F (85°C). Note ENGINE SPEED and BNK 1 SEN 2 display. Operate engine at 1200-2000 RPM for about 2 minutes. After 2 minutes check if rear oxygen sensor voltage rapidly swings from less than .3 volt to greater than .6 volt. If oxygen sensor voltage is swinging as specified, go to next step. If oxygen sensor voltage is not swinging as specified, go to step 6).
5. With engine running at 1200-2000 RPM, note scan tool display LOOP STATUS. If display indicates CLOSED, fault is not present. See DIAGNOSTIC AIDS. If display does not indicate CLOSED, go to step 9).
6. If rear oxygen sensor voltage remains between .3-.6 volt longer that it swings out of this range, go to step 9). If oxygen sensor voltage swings, go to next step.
7. Check terminal contact at PCM harness connector C2. Repair as necessary. If terminal contact is okay, go to next step.
8. Check terminal contact at pre-converter oxygen sensor connector. Repair as necessary. If harness connector is okay, go to next step.
9. Replace pre-converter oxygen sensor. Check for possible sensor contamination, i.e. leaded fuel, incorrect gasket seal or over rich operation. If failure is caused by over rich condition, check fuel injection system. See BASIC TESTING article.

If fault is not present, check PCM grounds. Never solder oxygen sensor wires.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Start engine. Using scan tool, select ENGINE 1 and observe ECT display. Operate engine until temperature reaches 185°F (85°C). Note ENGINE SPEED and BNK 1 SEN 2 display. Operate engine at 1200-2000 RPM for about 2 minutes. After 2 minutes check if rear oxygen sensor voltage rapidly swings from less than .3 volt to greater than .6 volt. If oxygen sensor voltage is swinging as specified, fault is not present. See DIAGNOSTIC AIDS. If oxygen sensor voltage is not swinging as specified, go to next step.
3. If pre-converter oxygen sensor voltage remains between .3-.6 volt longer that it swings out of this range, go to step 6). If oxygen sensor voltage swings, go to next step.
4. Check terminal contact at PCM harness connector C2. Repair as necessary. If terminal contact is okay, go to next step.
5. Check terminal contact at pre-converter oxygen sensor connector. Repair as necessary. If harness connector is okay, go to next step.
6. Replace pre-converter oxygen sensor. Check for possible sensor contamination, i.e. leaded fuel, incorrect gasket seal or over rich operation. If failure is caused by over rich condition, check fuel injection system. See BASIC TESTING article.

If fault is not present, check PCM grounds. Never solder oxygen sensor wires.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. If you were sent here from another DTC, go to step 4). If not, go to next step.
3. Using scan tool, check if other DTC(s) are present. If other DTC(s) are present, diagnose affected DTC(s) first. If no other DTC(s) are present, go to next step.
4. Start engine. Using scan tool, select ENGINE 1 and observe ECT display. Operate engine until temperature reaches 185°F (85°C). Note ENGINE SPEED and BNK 2 SEN 1 display. Operate engine at 1200-2000 RPM for about 2 minutes. After 2 minutes check if pre-converter oxygen sensor voltage rapidly swings from less than .3 volt to greater than .6 volt. If oxygen sensor voltage is swinging as specified, go to next step. If oxygen sensor voltage is not swinging as specified, go to step 6).
5. With engine running at 1200-2000 RPM, note scan tool display LOOP STATUS. If display indicates CLOSED, fault is not present. See DIAGNOSTIC AIDS. If display does not indicate CLOSED, go to step 9).
6. If pre-converter oxygen sensor voltage remains between .3-.6 volt longer that it swings out of this range, go to step 9). If oxygen sensor voltage swings, go to next step.
7. Check terminal contact at PCM harness connector C2. Repair as necessary. If terminal contact is okay, go to next step.
8. Check terminal contact at pre-converter oxygen sensor connector. Repair as necessary. If harness connector is okay, go to next step.
9. Replace pre-converter oxygen sensor. Check for possible sensor contamination, i.e. leaded fuel, incorrect gasket seal or over rich operation. If failure is caused by over rich condition, check fuel injection system. See BASIC TESTING article.

If fault is not present, check PCM grounds. Never solder oxygen sensor wires.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check if other DTC(s) are present. If other DTC(s) are present, diagnose affected DTC(s) first. If no other DTC(s) are present, go to next step.
3. Start engine. Using scan tool, select ENGINE 1 and observe ECT display. Operate engine until temperature reaches 185°F (85°C). Note ENGINE SPEED and BNK 2 SEN 1 display. Operate engine at 1200-2000 RPM for about 2 minutes. After 2 minutes, check if front oxygen sensor voltage rapidly swings from less than .3 volt to greater than .6 volt. If oxygen sensor voltage is swinging as specified, go to next step. If oxygen sensor voltage is not swinging as specified, go to step 5).
4. With engine at 1200-2000 RPM, note scan tool LOOP STATUS display. If scan tool display reads CLOSED, fault is not present. See DIAGNOSTIC AIDS. If scan tool display does not read CLOSED, go to step 8).
5. If front oxygen sensor voltage remains between .3-.6 volt longer that it swings out of this range, go to step 8). If oxygen sensor voltage swings, go to next step.
6. Check terminal contact at PCM harness connector C2. Repair as necessary. If terminal contact is okay, go to next step.
7. Check terminal contact at front oxygen sensor connector. Repair as necessary. If harness connector is okay, go to next step.
8. Replace front oxygen sensor. Check for possible sensor contamination, i.e. leaded fuel, incorrect gasket seal or over rich operation. If failure is caused by an over rich condition, check fuel injection system. See BASIC TESTING article.

If fault is not present, check PCM grounds. Never solder oxygen sensor wires.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check if DTC P0108 or P1114 is set. If any of these DTC(s) are present, diagnose affected DTC(s). If DTC(s) are not present, diagnose cooling system.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check if DTC(s) P0322, P1323 or P1375 is also present. If any of the DTC(s) are present, diagnose affected DTC(s) first. If DTC(s) are not present, go to next step.
3. Disconnect IC module harness connector C3. Turn ignition on. Using DVOM, check voltage between ground and ignition feed circuit at IC module harness connector C3 terminal. If voltage is 10 volts or greater, go to next step. If voltage is less than 10 volts, go to step 10).
4. Turn ignition off. Reconnect IC module harness connector C3. Disconnect IC module harness connector C4. Store fluid life index as indicated on scan tool. Disconnect PCM harness connector C2. Using DVOM, check resistance between ground and fuel control circuit at PCM harness connector terminal. If resistance is greater than 10,000 ohms go to next step. If resistance is not greater than 10,000 ohms, go to step 11).
5. Check resistance of fuel control circuit between IC module harness connector and PCM harness connector terminal. If resistance is 5 ohms or less, go to next step. If not 5 ohms or less, step 12).
6. Turn ignition on. Check voltage between ground and fuel control circuit at IC harness connector C2 terminal. If voltage is less than .5 volt go to next step. If not, go to step 13).
7. Reconnect IC module harness connector C4. Check voltage between ground and fuel control circuit at PCM harness connector C2. If voltage is greater than 4.2 volts, go to next step. If voltage is 4.2 volts or less, go to step 14).
8. Turn ignition off. Disconnect IC module harness connector C2. Using 6-Pin IC Module Diagnostic Jumpers, jumper the following IC module connector C4 terminals to the following module terminals: C4 Terminal "A" To Module Pin "A" C4 Terminal "B" To Module Pin "B" C4 Terminal "C" To Module Pin "C" C4 Terminal "D" To Module Pin "D" C4 Terminal "E" To Module Pin "E" C4 Terminal "F" To Module Pin "F" Set DVOM to 400 mV AC scale and push Hz button. Connect DVOM between terminal "C" jumper and ground. Start engine and check frequency. If frequency is less than 30 Hz, go to step 10). If frequency is not less than 30 Hz, go to next step.
9. Remove all jumper wire connections. Reconnect IC module connector C4. Clear DTC. Start and idle engine. Using scan tool, select DTC INFO then FAIL THIS IGN modes. If DTC P1320 resets, go to step 16). If DTC does not reset, fault is not present. See DIAGNOSTIC AIDS.
10. Check for no voltage to IC module caused by a faulty fuse due to short in ignition feed circuit, open in ignition feed circuit or shorted IC module. Repair as necessary.
11. Repair short to ground in fuel control circuit to IC module.
12. Repair open in fuel control circuit to IC module.
13. Repair short to voltage in fuel control circuit to IC module.
14. Check terminal contact at IC module harness connector C4. Repair as necessary. If terminal contact is okay, go to next step.
15. Replace IC module.
16. Check fuel control circuit terminal contact at PCM harness connector C2. Repair as necessary. If terminal contact is okay, go to next step.
17. Replace PCM. Program replacement PCM using required equipment.

DTC may set due to a false start condition in which cranking speed exceeds 568 RPM with engine not starting. If no fault is present, check for intermittent open or short in IC module fuel control circuit, ignition feed circuit or ground circuit. Also, check for EMI interference on IC module fuel control circuit.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check if DTC P1376 is also present. If DTC P1376 is present, diagnose this DTC first. If DTC is not present, go to next step.
3. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect IC module harness connector C4 and PCM harness connector C2. Using DVOM, check resistance between ground and 24X reference circuit at PCM harness connector C2 terminal. If resistance is greater than 10 k/ohms, go to next step. If resistance is less than 10 k/ohms, go to step 8).
4. Check resistance of 24X reference signal circuit between PCM and IC harness connector terminals. If resistance is 5 ohms or less, go to next step. If resistance is greater than 5 ohms, go to step 9).
5. Reconnect IC module harness connector C4. Turn ignition on. Check voltage between ground and 24X reference signal circuit at PCM harness connector C2. If voltage is greater than 4.2 volts, go to next step. If voltage is 4.2 volts or less, go to step 10).
6. Turn ignition off. Disconnect IC module harness connector C2. Using 6-Pin IC Module Diagnostic Jumpers, jumper the following IC module connector C4 terminals to the following module terminals: C4 Terminal "A" To Module Pin "A" C4 Terminal "B" To Module Pin "B" C4 Terminal "C" To Module Pin "C" C4 Terminal "D" To Module Pin "D" C4 Terminal "E" To Module Pin "E" C4 Terminal "F" To Module Pin "F" Set DVOM to 400 mV AC scale and push Hz button. Connect DVOM between terminal "A" jumper and ground. Start engine and check frequency. If frequency is less than 340 Hz, go to step 10). If frequency is not less than 340 Hz, go to next step.
7. Remove all jumper wire connections. Reconnect IC module connector C4. Clear DTC. Start and idle engine. Using scan tool, select DTC INFO then FAIL THIS IGN modes. If DTC P1323 resets, go to step 13). If DTC does not reset, fault is not present. See DIAGNOSTIC AIDS.
8. Check for short to ground in 24X reference signal circuit.
9. Repair short to ground in 24X reference signal circuit.
10. Check terminal contact at IC module harness connector C4. Repair as necessary. If terminal contact is okay, go to next step.
11. Replace IC module.
12. Check 24X reference signal circuit terminal contact at PCM harness connector C2. Repair as necessary. If terminal contact is okay, go to next step.
13. Replace PCM. Program replacement PCM using required equipment.

DTC may set due to a false start condition in which cranking speed exceeds 568 RPM with engine not starting. If no fault is present, check for intermittent open or short in IC module fuel control circuit, ignition feed circuit or ground circuit. Also, check for EMI interference on IC module 24X reference signal circuit.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC P0322, P0372, P1323, P1371 or P1376 is also present. If any of these DTC(s) are present, diagnose affected DTC(s) first. If DTC(s) are not present, go to next step.
3. Using scan tool, select DTC and select FAILURE REC and note ENGINE SPEED snapshot display for DTC P1350. If engine speed display reads less than 500 RPM, go to next step. If engine speed display reads greater than 500 RPM, go to step 9).
4. Turn ignition off. Disconnect IC module harness connector C4. Using 6-Pin IC Module Diagnostic Jumpers, jumper the following IC module connector C4 terminals to the following module terminals: C4 Terminal "A" To Module Pin "A" C4 Terminal "B" To Module Pin "B" C4 Terminal "C" To Module Pin "C" C4 Terminal "D" To Module Pin "D" C4 Terminal "E" To Module Pin "E" C4 Terminal "F" To Module Pin "F" Turn ignition on. Using DVOM, check voltage between terminal "D" jumper and ground. If voltage is less than .4 volt, go to next step. If voltage is greater than .4 volt, go to step 7).
5. Remove injector fuses from underhood fuse/relay block. Crank engine and check voltage on terminal "E" jumper. If voltage reading is 1.3 volts or greater, go to next step. If voltage reading is less than 1.3 volts, fault is not present. See DIAGNOSTIC AIDS.
6. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2 and disconnect all jumpers from IC module connector. Check resistance of IC signal circuit between PCM harness connector and IC module harness connector terminals. If resistance is 5 ohms or less, go to step 25). If resistance is greater than 5 ohms, go to step 19).
7. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Using DVOM, check voltage reading. If voltage is .4 volt or less, go to next step. If voltage reading is greater than .4 volt, go to step 27).
8. Turn ignition off. Disconnect all jumper wires, but leave IC module harness connector C4 disconnected. Turn ignition on. Check voltage between ground and by-pass circuit at PCM harness connector terminal. If voltage reading is .4 volt or greater, go to step 20). If voltage reading is less than .4 volt, go to step 25).
9. Turn ignition off. Disconnect IC module harness connector C4. Using 6-Pin IC Module Diagnostic Jumpers, jumper the following IC module connector C4 terminals to the following module terminals: C4 Terminal "A" To Module Pin "A" C4 Terminal "B" To Module Pin "B" C4 Terminal "C" To Module Pin "C" C4 Terminal "D" To Module Pin "D" C4 Terminal "E" To Module Pin "E" C4 Terminal "F" To Module Pin "F" Start engine. Using DVOM, check voltage between terminal "D" jumper and ground. If voltage reading is 4.1 volts or greater, go to next step. If voltage reading is less than 4.1 volts, go to step 17).
10. Turn ignition off. Remove all jumper connectors, leaving IC module harness connector disconnected. Disconnect PCM harness connector C2. Using DVOM, check by-pass circuit between IC module connector and PCM connector terminals. If resistance is 5 ohms or less, go to next step. If resistance is greater than 5 ohms, go to step 21).
11. Reconnect PCM harness connector C2 and IC module harness connector jumpers. Set DVOM to 4-volt scale and push the Hz button. Start engine. Connect DVOM between jumper "E" terminal and ground. Frequency reading should be 30-100 Hertz. If frequency is as specified, fault is not present. See DIAGNOSTIC AIDS. If frequency is as specified, go to next step.
12. Set DVOM to DC voltage scale.With engine running check voltage at jumper "E" terminal and ground. If voltage reading is 4 volts or less, go to next step. If voltage reading is greater than 4 volts, go to step 15).
13. Turn ignition off. Disconnect jumpers from IC module harness connector C4. Set DVOM to PEAK MIN/MAX setting. Turn ignition on. Check voltage between ground and ignition control circuit at IC module harness connector C4 terminal. If voltage reading is 3.7 volts or less, go to next step. If voltage reading is greater than 3.7 volts, go to step 25).
14. Turn ignition off. Disconnect PCM harness connector C2. Check resistance between ground and ignition control circuit at IC module harness connector terminal. If resistance is 10,000 ohms or less, go to step 22). If resistance is greater than 10,000 ohms, go to step 27).
15. Turn ignition off. Disconnect jumpers from IC module harness connect C4. Turn ignition on. Check voltage between ground and ignition control circuit at IC module harness connector C4 terminal. If voltage reading is 1.3 volts or less, go to step 25). If voltage reading is greater than 1.3 volts, go to next step.
16. Turn ignition off. Disconnect PCM harness connector C2. Turn ignition on. Check voltage between ground and ignition control circuit at IC module harness connector C4. If voltage is greater than .5 volt, go to step 23). If voltage is less than .5 volt, go to step 27).
17. Turn ignition off. Disconnect jumpers from IC module harness connector. Disconnect PCM harness connector C2. Check resistance between ground and by-pass signal circuit at PCM harness connector terminal. If resistance is less than 5000 ohms, go to step 24). If resistance is greater than 5000 ohms, go to next step.
18. Reconnect PCM harness connector C2. Reconnect all jumper wires at IC module harness connector C4. Turn ignition on. Clear all DTC(s). Turn ignition off. Disconnect EGR harness connector. Jumper EGR harness connector terminal "D" (5-volt reference) to IC module harness connector C4 jumper "D" terminal. Start engine. Check if DTC P1350 resets. If DTC resets, go to step 27). If DTC does not reset, go to step 25).
19. Repair open in ignition control circuit.
20. Repair short to voltage in bypass signal circuit.
21. Repair open in by-pass signal circuit.
22. Repair short to ground in ignition control circuit.
23. Repair short to voltage in ignition control circuit.
24. Repair short to ground in by-pass signal circuit.
25. Check terminal contact at IC module harness connector C4. Repair as necessary. If terminal is okay, go to next step.
26. Replace IC module.
27. Check terminal contact at PCM harness connector C2. Repair as necessary. If terminal contacts are okay, go to next step.
28. Replace PCM. Program replacement PCM using required equipment.

If fault is not present, check terminal contact at IC module and PCM harness connectors.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Check for possible sources of Electromagnetic Interference (EMI), such as spark wires routed too close to IC module, high power transmitter operating in the vicinity or a battery charger causing EMI. Correct problem, if present. If EMI is not present, go to next step.
3. Clear DTC(s) and retest. If DTC P1370 resets, go to next step. If DTC does not reset, fault is not present.
4. Check fuel control circuit terminal contact IC module connector C4 and PCM harness connector C2. Repair as necessary. If terminal contacts are okay, go to next step.
5. Replace IC module.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check if DTC(s) P0322 or P1302 is also present. If DTC(s) are present, diagnose affected DTC(s) first. If DTC(s) are not present, go to next step.
3. Check for possible sources of Electromagnetic Interference (EMI), such as spark wires routed too close to IC module, high power transmitter operating in the vicinity or a battery charger causing EMI. Correct problem, if present. If EMI is not present, go to next step.
4. Clear DTC(s) and retest. If DTC P1371 resets, go to next step. If DTC does not reset, fault is not present. See DIAGNOSTIC AIDS.
5. Check fuel control circuit terminal contact in IC module connector C4 and PCM harness connector C2. Check for possible open or short in fuel control signal circuit. Repair as necessary. If terminal contacts or circuits are okay, go to next step.
6. Replace IC module.

An intermittent short or open to ground in the fuel control circuit to the PCM may set DTC. Check terminals carefully.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC P1376 is also present. If DTC P1376 is present, diagnose DTC first. If DTC P1376 is not present, go to next step.
3. Turn ignition off. Disconnect IC module harness connector C1. Using DVOM, check resistance between IC module harness connector terminals "A" and "B". If resistance is 800-1600 ohms, go to next step. If resistance is not as specified, go to step 11).
4. Check resistance between IC module harness connector terminals "E" and "F". If resistance is 800-1600 ohms, go to next step. If resistance is not as specified, go to step 14).
5. Check resistance between ground and IC module harness connector C1, terminals "A", then "B", then "E" and then "F". If resistance is less than 1000 ohms at each terminal, go to step 17). If resistance is greater than 1000 ohms, go to next step.
6. Disconnect IC module harness connector C3. Set DVOM to PEAK MIN/MAX 4-volt scale, 1 ms sampling rate. Measure the MAX DC voltage across IC module harness connector C1 terminals "A" and "B". Crank engine for 10 seconds. If voltage is greater than .25 volt while cranking engine, go to next step. If voltage is less than .25 volt, go to step 19).
7. Check MAX DC voltage across IC module harness connector C1 terminals "E" and "F". Crank engine for 10 seconds. If voltage is greater than .25 volt while cranking engine, go to next step. If voltage is less than .25 volt, go to step 20).
8. Reconnect IC module harness connectors C1 and C3. Disconnect IC module harness connector C4. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Check voltage between ground and PCM harness connector C2 terminal No. 5. If voltage is less than .4 volt, go to next step. If voltage is greater than specified, go to step 18).
9. Turn ignition off. Disconnect IC module harness connector C2. Using 6-Pin IC Module Diagnostic Jumpers, jumper the following IC module connector C4 terminals to the following module terminals: C4 Terminal "A" To Module Pin "A" C4 Terminal "B" To Module Pin "B" C4 Terminal "C" To Module Pin "C" C4 Terminal "D" To Module Pin "D" C4 Terminal "E" To Module Pin "E" C4 Terminal "F" To Module Pin "F" Turn ignition on. Set DVOM to 400 mV AC scale and push the Hertz button. Start engine. Connect DVOM between jumper "A" and ground. If frequency reading is greater than zero Hertz, go to next step. If frequency reading is less than zero Hertz, go to step 25).
10. Clear all DTC(s). Disconnect terminal "A" jumper only. Start engine. Using scan tool in DTC INFO mode, select FAIL THIS IGN function. If DTC P1323 is present, fault is not present. If DTC P1323 is not present, go to step 27).
11. If resistance was lower in step 3) than the range that was specified, go to next step. If resistance was higher than the range that was specified, go to step 27).
12. Disconnect crank sensor "A" harness connector. Check resistance across crank sensor harness connector terminals "A" and "B". If resistance is less than 10,000 ohms, go to step 21). If resistance is greater than specified, go to step 19).
13. Disconnect crank sensor "A" harness connector. Jumper crank sensor harness connector terminals "A" and "B" together. Check resistance between PCM harness connector C1 terminals "A" and "B". If resistance is greater than 5 ohms, go to step 22). If resistance is less than 5 ohms, go to step 19).
14. If resistance was lower in step 4) than the range that was specified, go to next step. If resistance was greater than the range that was specified, go to step 16).
15. Disconnect crank sensor "B" harness connector. Check resistance across crank sensor harness connector terminals "A" and "B". If resistance is less than 10,000 ohms, go to step 23). If resistance is greater than specified, go to step 20).
16. Disconnect crank sensor "B" harness connector. Jumper crank sensor harness connector terminals "A" and "B" together. Check resistance between PCM harness connector C1 terminals "E" and "F". If resistance is greater than 5 ohms, go to step 24). If resistance is less than 5 ohms, go to step 20).
17. Repair short to ground in circuit(s) that measured low in step 5).
18. Repair short to voltage in 24X spark reference circuit between IC module and PCM.
19. Replace crank sensor "A".
20. Replace crank sensor "B".
21. Repair crank sensor "A" circuits that are shorted together.
22. Repair open in either crank sensor "A" circuits.
23. Repair crank sensor "B" circuits that are shorted together.
24. Repair open in either crank sensor "B" circuits.
25. Check terminal contact at IC module harness connector C1 terminals 11A", "B", "E" or "F".
26. Replace IC module.
27. Check terminal contact at PCM harness connector terminal No. 5. Repair as necessary. If terminal contact is okay, go to next step.
28. Replace PCM. Program replacement PCM using required equipment.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, select FAILURE REC. in DTC mode. Note REF VOLTS LOW display when this DTC set. If voltage reading is 1.4 volts or greater, go to next step. If voltage reading is less than 1.4 volts, go to step 8).
3. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Disconnect IC module harness connector C4. Turn ignition on. Using scan tool, check voltage between ground and reference low circuit at PCM harness connector C4 terminal. If voltage is greater than .1 volt, go to step 9). If voltage is less than .1 volt, go to next step.
4. Check resistance of reference low circuit between IC module harness connector and PCM harness connector terminals. If resistance is 5 ohms or greater, go to step 10). If resistance is less than 5 ohms, go to next step.
5. Turn ignition key on. Check voltage to ground at reference low circuit at IC module harness connector C4 terminal. If voltage reading is .1 volt or greater, go to next step. If voltage reading is less than .1 volt, fault is not present. See DIAGNOSTIC AIDS.
6. Turn ignition off. Disconnect IC module harness connector C3. Check resistance to ground at IC module harness connector C3 terminal "A" (ground circuit). If resistance is 5 ohms or greater, go to step 11). If resistance is less than 5 ohms, go to next step.
7. Check terminal contact at IC module and PCM harness connectors. Check PCM and IC module ground connections. Repair as necessary. Reconnect all harness connectors. Clear this DTC. Start engine. If DTC resets, go to step 13). If DTC does not reset, fault is not present.
8. Turn ignition off. Disconnect both PCM harness connectors. Using DVOM, check resistance between ground and PCM ground circuits in PCM terminal. If resistance is greater than 5 ohms in any of the terminals, go to step 12). If not, check PCM grounds.
9. Repair short to voltage in reference low circuit.
10. Repair open in reference low circuit.
11. Repair open in ground circuit to IC module.
12. Repair open in circuits that had high resistance.
13. Replace IC module.

This DTC may set due to an improperly installed PCM, causing PCM not to be electrically isolated from body ground.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. If any other DTC(s) are present, diagnose affected DTC(s) first. If no other DTC(s) are present, go to next step.
3. If this DTC is set along with a driveability complaint, go to next step. If DTC is not set along with a driveability complaint, fault is not present, see DIAGNOSTIC AIDS.
4. This DTC will set when are too many or too few cam or 4X pulses. Check for Electromagnetic Interference (EMI) being induced in the fuel control circuit, cam signal circuit or camshaft position sensor circuits by improper spark plug wire routing or high power transmitter operating in the vicinity. Correct any causes of EMI. If EMI is not present, go to next step.
5. Check for intermittent short to ground, circuit shorted together or open in fuel control circuit, cam signal circuit or camshaft position sensor circuits. Repair as necessary. If circuits are okay, go to next step.
6. Check terminal contacts at camshaft position sensor terminals. Repair as necessary. If terminal contacts are okay, go to next step.
7. Check terminal contact at camshaft position sensor to IC module. Check terminal contact at fuel control circuit and cam signal circuit to PCM. Repair as necessary. If terminal contacts are okay, fault is not present. See DIAGNOSTIC AIDS.

Since this DTC can set under normal conditions, no diagnosis should be performed unless a driveability complaint is present. This DTC may also set if all 4 camshafts are off by one tooth (10 degrees BTDC), causing a severe driveability problem.

This DTC is used to determine when the EBTCM has lost the ability to provide rough road data to the PCM for misfire detection (DTC P0300). When the PCM sees that this condition is present, through the serial data, DTC will set.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, select DTC INFO and note if this DTC has failed this ignition cycle. If DTC failed, diagnose EBTCM system. If DTC did fail this ignition, go to next step.
3. Check EBTCM system for any history ABS/TCS DTC(s) or system problems. If any other DTC(s) or problems are noted, diagnose EBTCM system using appropriate ANTI-LOCK BRAKE SYSTEM article in the BRAKES section. If not other DTC(s) are present, fault is not present. See DIAGNOSTIC AIDS.

If this DTC is set along DTC P0300, it may represent an invalid misfire due to loss of rough road data. Several ABS system problems could cause a loss of rough road indication from EBTCM. All ABS/TCS system problems and DTC(s) should be corrected first, then duplicate the conditions under which DTC P1380 set and see if problem reoccurs.

DTC P1380 Schematic. Scheme 15

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, select DTC INFO and note if this DTC has failed this ignition cycle. If this DTC failed, diagnose EBTCM system. See appropriate ANTI-LOCK BRAKE SYSTEM article in the BRAKES section. If DTC has not failed this ignition cycle, go to next step.
3. Check EBTCM system for any history ABS/TCS DTC(s) or system problems. If any DTC(s) or problems are noted, diagnose EBTCM. If no DTC(s) or problems are noted, fault is not present.

If this DTC is set along with DTC P0300, it may represent an invalid misfire due to a loss of rough road data.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, select ENGINE 1 and note EGR PINTLE POS display reading. If voltage reading is within a range of 0.18-2.06 volts, go to next step. If voltage reading is not as specified, go to step 8).
3. In MISC TESTS mode, select OUTPUT TESTS then LINEAR EGR. Command EGR to 0. Note EGR PINTLE POS display reading. If voltage reading is one volt or less, go to next step. If voltage reading is greater than one volt, go to step 20).
4. Command EGR to 50%. Note EGR PINTLE POS display reading. If voltage reading is within a range of 2-3 volts, go to next step. If voltage reading is not as specified, go to step 21).
5. Command EGR to 100%. Note EGR PINTLE POS display reading. If voltage reading is 4 volts or greater, go to next step. If voltage reading is less than 4 volts, go to step 22).
6. In DTC mode, select FREEZE FRAME or FAILURE REC. Note EGR PINTLE POS display when DTC was set. If voltage reading is .18 volt or greater, go to next step. If voltage reading is less than .18 volt, go to step 23).
7. If voltage reading is 5 volts or greater, go to step 24). If voltage reading is less than 5 volts, go to step 26).
8. If voltage reading is .18 volt or less, go to next step. If voltage reading is .18 volt or greater, go to step 16).
9. Exit MISC TESTS. Switch to ENGINE 1 and note EGR PINTLE POS. Disconnect EGR harness connector. Using a jumper wire, jumper EGR position feedback and 5-volt reference circuits at EGR harness connector terminals. If voltage reading is .18 volt or less, go to next step. If voltage reading is greater than .18 volt, go to step 15).
10. Using DVOM, check voltage to ground on jumper wire. If voltage is less than 4.5 volts, go to next step. If voltage is greater than 4.5 volts, go to step 26).
11. Remove jumper sire. Check voltage to ground on EGR 5-volt reference circuit at EGR harness connector terminal. If voltage is 4.5 volts or less, go to next step. If voltage is greater than 4.5 volts, go to step 27).
12. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, the disconnect PCM harness connector C1. Check resistance between ground and 5-volt reference circuit at EGR harness connector terminal. If resistance is greater than 10,000 ohms, go to next step. If resistance is less than 10,000 ohms, go to step 28).
13. Check resistance of 5-volt reference circuit between PCM and EGR harness connector terminals. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, go to step 29).
14. Check 5-volt reference circuit terminal contact at PCM harness connector. Repair as necessary. If terminal contact is okay, go to step 35).
15. Check terminal contact at EGR harness connector. Repair as necessary. If terminal contact is okay, go to step 34).
16. Exit MISC TESTS. In ENGINE 1, note EGR PINTLE POS. Disconnect EGR harness connector. If voltage is less than 2.06 volts, go to next step. If voltage is greater than 2.06 voltage, go to step 30).
17. Using DVOM, check voltage between ground and EGR pintle position ground circuit at EGR valve harness connector terminal. If voltage reading is .1 volt or less, go to next step. If voltage reading is greater than .1 volt, go to step 31).
18. Check voltage between ground and EGR 5-volt reference signal circuit at EGR valve harness connector terminal. If voltage reading is 5.5 volts or less, go to next step. If voltage reading is greater than 5.5 volts, go to step 32).
19. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Check resistance of EGR pintle position ground circuit between PCM and EGR valve harness connector terminals. If resistance is less than 5 ohms, go to step 15). If resistance is greater than 5 ohms, go to step 33).
20. Check for poor terminal contact at EGR valve and PCM harness connector C1. Check for high resistance in EGR pintle position ground circuit, sticky EGR valve or intermittent short to voltage in EGR position feedback circuit, 5-volt reference signal circuit or EGR pintle position ground circuit. Repair as necessary. If circuits are okay, fault is not present.
21. Check terminal contact at PCM and EGR harness connectors. Check for sticky EGR valve. Repair as necessary. If circuit or EGR valve is okay, fault is not present.
22. Check terminal contact at PCM and EGR harness connector. Check for high resistance in EGR position feedback signal circuit or 5-volt reference signal circuit. Check for sticky EGR valve. Repair as necessary. If circuits or EGR valve is okay, fault is not present.
23. Check for intermittent open or short to ground in EGR pintle position ground circuit and 5-volt reference signal circuit. Repair as necessary. If circuits are okay, fault is not present.
24. Check for intermittent open in 5-volt reference signal circuit. Check for intermittent short to voltage in EGR feedback position signal circuit, 5-volt reference signal circuit or EGR pintle position ground circuit. Repair as necessary. If circuits are okay, fault is not present.
25. Check for intermittent open or short in EGR ignition feed circuit or EGR valve control signal circuit. Check for sticky EGR valve. Repair as necessary. If circuits or EGR valve are okay, fault is not present.
26. Repair open in EGR feedback position signal circuit. Repair as necessary.
27. Repair short to ground in EGR position feedback signal circuit. Repair as necessary.
28. Repair short to ground in EGR 5-volt reference signal circuit. Repair as necessary.
29. Repair open in EGR 5-volt reference signal circuit. Repair as necessary.
30. Repair short to voltage in EGR position feedback circuit. Repair as necessary.
31. Repair short to voltage in EGR pintle position ground circuit. Repair as necessary.
32. Repair short to voltage in EGR 5-volt reference signal circuit. Repair as necessary.
33. Repair open in EGR pintle position ground circuit. Repair as necessary.
34. Replace EGR valve.
35. Replace PCM. Program replacement PCM using required equipment.

1. Perform Powertrain On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC P1645 is also present. If DTC P1645 is present, diagnose DTC first. If DTC P1645 is not present, go to next step.
3. Turn ignition off. Remove fuel cap for about 10 seconds. Replace fuel cap. Turn ignition on, with engine off. Using scan tool, select ENGINE 2 and note EVAP VACUUM SW display. If scan tool displays PURGING, go to step 9). If scan tool does not display PURGING, go to next step.
4. While observing EVAP VACUUM SWITCH display, start and idle engine. If scan tool displays PURGING, go to next step. If scan tool does not display PURGING, fault is not present. See DIAGNOSTIC AIDS.
5. Note EVAP PURGE SOL display. If scan tool shows duty cycle less than 9.8%, go to step 7). If scan tool shows duty cycle at greater than 9.8%, go to next step.
6. Select MISC TESTS, then OUTPUT TESTS, then EVAP PURGE. Command EVAP purge solenoid OFF (0%). Note EVAP VACUUM SW display. If scan tool displays PURGING, go to next step. If scan toll does not display PURGING, fault is not present. See DIAGNOSTIC AIDS.
7. Check all vacuum lines for proper routing. Repair as necessary. If vacuum line routings are okay, go to next step.
8. Replace EVAP solenoid.
9. Disconnect EVAP vacuum switch. Using jumper wire, jumper EVAP vacuum switch harness connector terminals. If scan tool display shows NO FLOW, go to step 12). If scan tool display does not show NO FLOW, go to next step.
10. Using DVOM, check voltage between ground and EVAP vacuum switch input signal circuit at harness connector terminal. If voltage reading is 10.5 volts or less, go to step 13). If voltage reading is greater than 10.5 volts, go to next step.
11. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Using DVOM, check resistance of EVAP vacuum switch input circuit between PCM harness connector and EVAP vacuum switch harness connector terminals. If resistance is 5 ohms or less, go to step 15). If resistance is greater than 5 ohms, go to step 14).
12. Replace EVAP vacuum switch.
13. Repair open in ground circuit between EVAP vacuum switch and ground.
14. Repair open in EVAP vacuum switch input circuit between switch and PCM harness connector terminal.
15. Check EVAP vacuum switch input circuit terminal contact at PCM harness connector. Repair as necessary. If terminal contact is okay, go to next step.
16. Replace PCM.

Since this test checks for open EVAP vacuum switch while EVAP solenoid is commanded OFF, an EVAP vacuum switch signal problem could set this DTC along with DTC P1442. If an EVAP switch problem is suspected, perform DTC P1442 diagnosis.

If a sticking solenoid is suspected, command EVAP solenoid ON and OFF several times while watching the EVAP switch for the correct display.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC(s) P1640 and P1645 is also present. If these DTC(s) are present, diagnose affected DTC(s) first. If DTC(s) are not present, go to next step.
3. Turn ignition off. Open fuel cap for about 10 seconds. Replace fuel cap. Turn ignition on. Using scan tool, select ENGINE 2 mode and note EVAP VACUUM SW. display. If scan tool display reads NO FLOW, fault is not present. See DIAGNOSTIC AIDS. If scan tool does not display does not read NO FLOW, go to next step.
4. Disconnect EVAP switch harness connector. Using jumper wire, jumper EVAP switch harness connector terminals. If scan toll display reads NO FLOW, go to step 7). If scan tool display does not read NO FLOW, go to next step.
5. Using DVOM, check voltage between ground and EVAP vacuum switch input circuit (terminal "A") at harness connector. If voltage reading is 10.5 volts or less, go to step 8). If voltage reading is greater than 10.5 volts, go to next step.
6. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM connector C2. Check resistance of EVAP vacuum switch input circuit between PCM harness connector and switch harness connector terminals. If resistance is 5 ohms or less, go to step 10). If resistance is greater than 5 ohms, go to step 9).
7. Replace EVAP vacuum switch.
8. Repair open in EVAP vacuum switch ground circuit.
9. Repair open in EVAP vacuum switch input circuit to PCM harness connector.
10. Check terminal contact at PCM harness connector C2. Repair as necessary. If terminal contact is okay, go to next step.
11. Replace PCM. Program replacement PCM using required equipment.

Never apply battery voltage to EVAP vacuum switch or switch damage will occur. Voltage supplied by PCM is low voltage.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Start and idle engine. Turn off all accessories. Using scan tool, select MISC TESTS and select IAC SYSTEM. Command engine speed up to 1500 RPM, down to 500 RPM, then back to 1500 RPM while monitoring ENGINE SPEED display. If ENGINE SPEED display remains within 50 RPM of desired value for each RPM command, fault is not present. If engine speed is not within 50 RPM of desired value, go to next step.
3. Disconnect IAC valve. Install IAC Noid Light (J 37027). Start engine. Command engine speed up to 1500 RPM, down to 500 RPM, then back to 1500 RPM while monitoring noid light. If noid light cycles Red and Green (never off), go to step 5). If noid light does not cycle, go to next step.
4. Check all IAC circuits for open, short to ground or short to voltage. Repair as necessary. If circuits are okay, go to step 8).
5. Check throttle body for objects blocking IAC passage or throttle bore, excessive deposits in IAC passage, pintle, throttle bore or throttle plate. Check for restriction or vacuum leaks in air intake system. Check adjustment screw for tampering. Repair as necessary. If no problems are found, go to next step.
6. Check for poor terminal contact at IAC harness connector. Repair as necessary. If terminal contacts are okay, go to next step.
7. Replace IAC valve.
8. Check IAC terminal contacts at PCM harness connector C1. Repair as necessary. If terminal contacts are okay, go to next step.
9. Replace PCM. Program replacement PCM using required equipment.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Start and idle engine. Turn off all accessories. Using scan tool, select MISC TESTS and select IAC SYSTEM. Command engine speed up to 1500 RPM, down to 500 RPM, then back to 1500 RPM while monitoring ENGINE SPEED display. If ENGINE SPEED display remains within 50 RPM of desired value for each RPM command, fault is not present. See DIAGNOSTIC AIDS. If engine speed is not within 50 RPM of desired value, go to next step.
3. Disconnect IAC valve. Install IAC Noid Light (J 37027). Start engine. Command engine speed up to 1500 RPM, down to 500 RPM, then back to 1500 RPM while monitoring noid light. If noid light cycles Red and Green (never off), go to step 5). If noid light does not cycle, go to next step.
4. Check all IAC circuits for open, short to ground or short to voltage. Repair as necessary. If circuits are okay, go to step 8).
5. Check throttle body for objects blocking IAC passage or throttle bore, excessive deposits in IAC passage, pintle, throttle bore or throttle plate. Check for restriction or vacuum leaks in air intake system. Check adjustment screw for tampering. Repair as necessary. If no problems are found, go to next step.
6. Check for poor terminal contact at IAC harness connector. Repair as necessary. If terminal contacts are okay, go to next step.
7. Replace IAC valve.
8. Check IAC terminal contacts at PCM harness connector C1. Repair as necessary. If terminal contacts are okay, go to next step.
9. Replace PCM. Program replacement PCM using required equipment.

Reviewing the FAILURE REC may help diagnose an intermittent failure by showing how long ago and under what conditions the DTC set.

The Park/Neutral Position (PNP) switch circuit is switched to ground in Park and Neutral. This test monitors the PNP switch for a false output. DTC will set if the switch is indicating Park or Neutral while driving conditions present indicate that transmission is in gear.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, observe Park/Neutral position parameter PNP, with vehicle in Park. If scan tool display reads P/N, go to next step. If scan tool display does not read P/N, go to step 7).
3. Move shifter from Park through all the ranges and back to Park while observing the Park/Neutral position parameter. If scan tool display reads P/N all the time, go to step 5). If scan tool display does not read P/N all the time, go to next step.
4. If scan tool display matches that range selected, fault is not present. See DIAGNOSTIC AIDS. If scan tool display does not match all the ranges selected, go to step 7).
5. Disconnect PNP switch harness connector. If scan tool display reads P/N, go to next step. If scan tool display does not read P/N, go to step 9).
6. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Using DVOM, check resistance between ground and PNP switch input circuit at harness connector terminal. If resistance is less than 10,00 ohms, go to step 8). If resistance is greater than specified, go to step 10).
7. Adjust PNP switch and shift lever.
8. Repair short to ground in PNP switch position input circuit.
9. Replace PNP switch.
10. Replace PCM. Program replacement PCM using required equipment.

Manipulate related wiring and connectors while observing transmission range switch input. If an intermittent is induced, the parameter display will change.

Attempt to crank engine while moving the shift lever. Since both the Neutral safety and Park/Neutral switch contacts are housed together, an out of adjustment switch could cause an intermittent no-crank conditions.

DTC P1520 Schematic. Scheme 16

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC P0121, P0122 or P0123 is present. If any of these DTC(s) are present, diagnose affected DTC(s) first. If these DTC(s) are not present, go to next step.
3. Select ENGINE 2 mode. Ensure foot is off accelerator pedal. Observe TP SENSOR display. If TP sensor reads 6.5 degrees or greater, go to step 5). If TP sensor reads less than 6.5 degrees, go to next step.
4. If TP sensor reads less than -6.5 degrees, go to step 8). If TP sensor reads greater than -6.5 degrees, go to next step.
5. Check for binding throttle and cruise control cables. Repair as necessary. After repairs, go to step 9). If throttle and cruise control cables are okay, go to next step.
6. Check for deposits on throttle body bore and blades. Clean as necessary. After cleaning throttle body, go to step 9). If throttle body did not need cleaning, go to next step.
7. Turn ignition on. Using scan tool, select ENGINE 2. Ensure foot is off accelerator pedal. Observe TP SENSOR display. If reading outside of a range of -6.5 to 6.5 degrees, go to next step. If reading is as specified, go to step 9).
8. Replace throttle body. After replacing throttle body, go to next step.
9. Perform "TP Learn Procedure".

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Check if DTC(s) P0120, P0121, P0122, P0123, P1121, P1122 or P1524 are also present. If any of these DTC(s) are present, diagnose affected DTC(s) first. If these DTC(s) are not present, go to next step.
3. Turn ignition off. Ensure throttle is fully closed. Turn ignition on and wait 30 seconds. Turn ignition off. After 30 seconds, repeat the step. After performing this step, go to next step.
4. With ignition off, wait 30 seconds. Turn ignition on. Using scan tool in DTC mode, select DTC INFO. If scan tool display indicate TEST RAN, TEST PASSED in this ignition cycle, system is okay. If scan tool display does not indicate TEST RAN, TEST PASSED in this ignition cycle, see DIAGNOSTIC AIDS.

Ensure nothing is touching or obstructing the accelerator or brake pedals during the TP learn procedure because this will prevent the PCM from performing the learn routine.

If DTC 1526 does not change to history code following the completion of the TP sensor learn procedure, this may be due to an incorrect or erratic signals from the TP sensor.

The A/C low side temperature sensor uses a thermistor to control the signal voltage to PCM. PCM applies 5 volts to A/C low temperature sensor circuit. When sensor is cold, sensor resistance is high and PCM will see a high signal voltage. As the sensor warms up, its resistance drops and signal voltage is pulled low through the ground circuit. This test detects a shorted to ground or open A/C low side temperature sensor circuit by setting DTC if the PCM monitors a signal voltage (temperature) that is too high or low.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool in ENGINE 3 mode, note A/C LOW SIDE TMP. display. If scan tool display reads -35 to 210°F (-37 to 99°C), fault is not present. Diagnose A/C-heater system. If scan tool display reads less than -35°F (-37°C) or greater than 210°F (99°C), go to next step.
3. If temperature displayed is less than -35°F (-37°C), go to next step. If temperature displayed is greater than -35°F (-37°C), go to step 7).
4. Turn ignition off. Disconnect sensor harness connector. Using jumper wire, jumper A/C low temperature sensor harness connector terminals. Turn ignition on. If temperature reading is greater than 210°F (99°C), go to step 12). If temperature reading is less than 210°F (99°C), go to next step.
5. Remove jumper wire from sensor harness connector. Jumper sensor harness connector terminal "A" to ground. If temperature reading is greater than 210°F (99°C), go to step 9). If temperature reading is less than 210°F (99°C), go to next step.
6. Remove jumper wire from sensor harness connector. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Using DVOM, check resistance of A/C low temperature sensor signal circuit between PCM and sensor harness connector terminals. If resistance is greater than 5 ohms, go to step 10). If resistance is less than 5 ohms, go to step 14).
7. Disconnect sensor harness connector. If temperature displayed is less than -35°F (-37°C), go to step 12). If temperature displayed is greater than -35°F (-37°C), go to next step.
8. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Using DVOM, check resistance between ground and A/C low temperature sensor circuit at PCM harness connector C1 terminal. If resistance is greater than 10,000 ohms, go to step 14). If resistance is less than 10,000 ohms, go to next step.
9. Repair open in A/C low temperature sensor ground circuit.
10. Repair open in A/C low temperature sensor circuit.
11. Repair short to ground in A/C low temperature sensor circuit.
12. Check terminal contact at sensor harness connector. Repair as necessary. If terminal contact is okay, go to next step.
13. Replace A/C low temperature sensor.
14. Check terminal contact at PCM harness connector C1. Repair as necessary. If terminal contact is okay, go to next step.
15. Replace PCM. Program replacement PCM using required equipment.

DTC P1533 Schematic. Scheme 17

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on, with engine off. Using scan tool in ENGINE 3 mode, note A/C HI SIDE TMP. display. If scan tool display reads 10 to 410°F (-12 to 210°C), fault is not present. Diagnose A/C-heater system. If scan tool display reads less than 10°F (-12°C) or greater than 410°F (210°C), go to next step.
3. If temperature displayed is greater than 410°F (210°C), go to step 7). If temperature displayed is less than specified, go to next step.
4. Turn ignition off. Disconnect sensor harness connector. Using jumper wire, jumper A/C high temperature sensor harness connector terminals. Turn ignition on. If temperature reading is greater than 410°F (210°C), go to step 12). If temperature reading is less than specified, go to next step.
5. Remove jumper wire from sensor harness connector. Jumper sensor harness connector terminal "A" to ground. If temperature reading is greater than 410°F (210°C), go to step 9). If temperature reading is less than specified, go to next step.
6. Remove jumper wire from sensor harness connector. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Using DVOM, check resistance of A/C low temperature sensor signal circuit between PCM and sensor harness connector terminals. If resistance is greater than 5 ohms, go to step 10). If resistance is less than 5 ohms, go to step 14).
7. Disconnect sensor harness connector. If temperature displayed is less than 10°F (-12°C), go to step 12). If temperature displayed is greater than 10°F (-12°C), go to next step.
8. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Using DVOM, check resistance between ground and A/C high temperature sensor circuit at PCM harness connector C1 terminal. If resistance is greater than 10,000 ohms, go to step 14). If resistance is less than 10,000 ohms, go to next step.
9. Repair open in A/C high temperature sensor ground circuit.
10. Repair open in A/C high temperature sensor circuit.
11. Repair short to ground in A/C high temperature sensor circuit.
12. Check terminal contact at sensor harness connector. Repair as necessary. If terminal contact is okay, go to next step.
13. Replace A/C high temperature sensor.
14. Check terminal contact at PCM harness connector C1. Repair as necessary. If terminal contact is okay, go to next step.
15. Replace PCM. Program replacement PCM using required equipment.

If this DTC sets due to a shorted condition, it could also set DTC P1539.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check if DTC(s) P0116, P0117 or P1114 is also present. If any of these DTC(s) is present, diagnose affected DTC(s). If DTC(s) are not present, see DIAGNOSTIC AIDS.

This DTC is associated with an overheating/low coolant level condition. Diagnose cooling system.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Start and idle engine. Turn on A/C to maximum cool and maximum fan (high speed). Using scan tool in DTC mode, select DTC INFO then select FAIL THIS IGN. Wait one minute and check if DTC sets. If DTC sets, go to next step. If DTC does not set, fault is not present. See DIAGNOSTIC AIDS.
3. Turn engine off. Disconnect A/C low pressure switch harness connector. Remove A/C compressor fuse or A/C clutch relay. Using scan tool in ENGINE 3 mode, select A/C REQUEST. Using a jumper wire, jumper A/C low pressure switch harness connector terminals. Start engine and turn A/C on. If scan tool displays YES, go to step 8). If scan tool does not display YES, go to next step.
4. Reinstall fuse or relay. Remove jumper. With engine running and A/C on, check voltage between ground and A/C low pressure switch harness connector terminal "A". If voltage reading is 10.5 volts or greater, go to next step. If voltage reading is less than 10.5 volts, go to step 7).
5. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Check resistance between ground and A/C low pressure switch circuit at harness connector. If resistance is less than 10,000 ohms, go to next step. If resistance is greater than 10,000 ohms, go to step 9).
6. Check resistance of A/C low pressure switch circuit between PCM harness connector and switch harness connector terminals. If resistance is 5 ohms or less, go to step 14). If resistance is greater than 5 ohms, go to step 10).
7. With engine on and A/C on, check voltage to ground at A/C-heater programmer terminal D15 (Dark Green/White wire). If voltage reading is 10.5 volts or greater, go to step 11). If voltage reading is less than 10.5 volts, go to step 13).
8. Reinstall fuse or relay. Install A/C manifold gauges to A/C system, and note low side pressure. If low side pressure is greater than 38 psi (2.7 kg/cm 2 ), go to step 12). If low side pressure is less than 38 psi (2.7 kg/cm 2 ), system pressure is low. Diagnose A/C-heater system.
9. Repair short to ground in A/C low pressure switch signal circuit.
10. Repair open in A/C low pressure switch signal circuit.
11. Repair open in A/C low pressure switch circuit to A/C-heater programmer.
12. Replace A/C low pressure switch.
13. Replace A/C-heater programmer.
14. Check terminal contacts for A/C low pressure switch at PCM harness connector C1. Repair as necessary. If terminal contact is okay, go to next step.
15. Replace PCM. Program replacement PCM using required equipment.

If fault is not present, operate vehicle with A/C manifold gauge connected and watch for low A/C system pressure with A/C on for an extended period. Whenever A/C request line is checked for voltage, engine must be running.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Start and idle engine. Turn on A/C to maximum cool and maximum fan (high speed). Using scan tool in DTC mode, select DTC INFO then select FAIL THIS IGN. Wait one minute and check if DTC sets. If DTC sets, go to next step. If DTC does not set, fault is not present.
3. In ENGINE 3 mode, note A/C REQUEST display on scan tool. If scan tool displays YES, go to next step. If scan tool does not display yes, go to step 10).
4. Disconnect A/C low pressure switch harness connector. In ENGINE 3 mode, select A/C REQUEST and note display on scan tool. If scan tool displays YES, go to step 6). If scan tool does not display YES, go to next step.
5. Reconnect low pressure switch harness connector. Remove A/C fuse. In ENGINE 3 mode, note A/C REQUEST display on scan tool. If scan tool displays YES, go to step 7). If scan tool does not display YES, go to step 9).
6. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Turn ignition on. Check voltage between ground and A/C low pressure switch circuit at harness connector. If voltage is greater .5 volt, go to step 8). If voltage is less than .5 volt, go to step 10).
7. Repair short to ground in A/C low pressure switch circuit to A/C-heater programmer.
8. Replace A/C-heater programmer.
9. Replace PCM. Program replacement PCM using required equipment.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC P1535 is present. If DTC P1535 is present, diagnose this DTC first. If DTC P1535 is not present, go to next step.
3. Using scan tool in ENGINE 3 mode, note A/C HI PRES. SW. display. If scan tool displays NORMAL, go to next step. If scan tool does not display NORMAL, go to step 6).
4. Disconnect A/C high pressure switch. If scan tool displays HI PRESS., go to step 10). If scan tool does not display HI PRESS., go to next step.
5. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Check resistance between ground and A/C high pressure switch circuit at harness connector. If resistance is less than 10,000 ohms, go to step 12). If resistance is greater than 10,000 ohms, go to step 16).
6. Disconnect A/C high pressure switch. Using a jumper wire, jumper A/C high pressure switch harness connector terminals together. If scan tool displays NORMAL, go to step 9). If scan tool does not display NORMAL, go to next step.
7. Jumper A/C high pressure switch signal circuit to ground. If scan tool displays NORMAL, go to step 14). If scan tool does not display NORMAL, go to next step.
8. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Check resistance between ground and A/C high pressure switch circuit at harness connector. If resistance is greater than 5 ohms, go to step 13). If resistance is less than 5 ohms, go to step 16).
9. Install A/C manifold gauges. If A/C high side pressure is greater than 430 psi (30 kg/cm 2 ), diagnose A/C system. If high side pressure is less than 430 psi (30 kg/cm 2 ), go to step 15).
10. Reconnect A/C high pressure switch connector. Start engine and turn on A/C. Note both the scan tool display A/C HI PRESS. SW. and A/C HIGH SIDE TEMP. readings. If temperature reading is greater than 203°F (95°C), go to next step. If temperature reading is less than 203°F (95°C), fault is not present. See DIAGNOSTIC AIDS.
11. If scan tool indicates HI PRESS., fault is not present. See DIAGNOSTIC AIDS. If scan tool does not indicate HI PRESS., go to step 15).
12. Repair short to ground in A/C high pressure switch signal circuit.
13. Repair open in A/C high pressure switch signal circuit.
14. Repair open in A/C high pressure switch ground circuit.
15. Replace A/C high pressure switch.
16. Replace PCM. Program replacement PCM using required equipment.

If A/C high side temperatures stays at less than 203°F (95°C), use the FAILURE REC and operate vehicle under the same conditions that set the DTC and observe the A/C high side temperature.

If A/C high side temperature increases to greater than 203°F (95°C) and the switch opens, check for an intermittent short to ground in A/C high pressure switch signal circuit. Repair as necessary.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Start engine and turn A/C on. Using scan tool in ENGINE 3 mode, note A/C HI PRESS. SW. display. If scan tool displays NORMAL, fault is not present. See DIAGNOSTIC AIDS. If scan tool does not display NORMAL, go to next step.
3. Turn engine off. Connect A/C manifold gauges. Start engine and turn A/C on. Monitor A/C high side pressure on manifold gauges and monitor A/C HI PRESS. SW. display on scan tool. If scan tool displays HI PRESS. and high pressure side is greater than 430 psi (30 kg/cm 2 ), go to step 7). If scan tool does not display HI PRESS. or if high pressure side is less than 430 psi (30 kg/cm 2 ), go to next step.
4. Turn ignition off. Disconnect A/C high pressure switch harness connector and PCM harness connector C1. Check terminal contact at both switch and PCM harness connectors. Repair as necessary. If terminal contacts are okay, go to next step.
5. Check for intermittent open in A/C high pressure switch signal circuit and ground circuit. Repair as necessary. If circuits are okay, go to next step.
6. Replace A/C high pressure switch.
7. Repair cause of high A/C system pressure.

Use the FAILURE REC mode on scan tool and note conditions under which the DTC set. If A/C HIGH SIDE TEMP. was close to 189°F (87°C), then a high pressure condition probably occurred. If A/C HIGH SIDE TEMP. was low, then an intermittent open circuit or switch probably set the DTC.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool in DTC mode, select FAILURE REC. and note the OUTSIDE AIR TEMP. display when the DTC is set. If outside temperature is exceedingly hot, system is okay. See DIAGNOSTIC AIDS. If outside temperature is not that hot, diagnose A/C system.

This DTC is used for system protection during a high temperature/pressure condition. This condition could occur normally if sufficient cooling of the A/C system cannot occur due to high ambient temperature.

PCM will not allow cruise control operation under certain conditions, such as when vehicle speed is too low. This is done by the PCM grounding the 12 volt cruise inhibit switch sent by the cruise control module. If PCM is allowing cruise operation and the operator is requesting for cruise control, the cruise control module will send a cruise engaged signal to the PCM.

This test is used to compare the cruise inhibit output versus the cruise engaged input. DTC will set when the PCM sees that the cruise control module is signaling that it is engaged by sending 12 volts to the cruise engaged circuit while the PCM is inhibiting cruise operation on the cruise inhibit output circuit.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check if DTC P1664 is also present. If DTC P1664 is present, diagnose DTC first. If DTC P1664 is not present, go to next step.
3. Turn ignition on. Using scan tool, select DTC INFO. If DTC P1554 has failed this ignition, go to next step. If scan tool indicates DTC did not fail this ignition, fault is not present. See DIAGNOSTIC AIDS.
4. Turn ignition off. Disconnect cruise control module harness connector. Turn ignition on. Using scan tool, select DTC INFO. If DTC P1554 has failed this ignition, go to step 7). If scan tool indicates DTC did not fail this ignition, go to next step.
5. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Turn ignition on. Using DVOM, check resistance between ground and cruise engaged output circuit terminal at cruise module. If resistance is less than 10 k/ohms, go to next step. If not, go to step 8).
6. Repair short to ground in cruise engaged input circuit.
7. Replace cruise control module.
8. Replace PCM. Program replacement PCM using required equipment.

Use of the FAILURE REC. mode on scan tool can help diagnose intermittent problems, by displaying how long ago and the conditions under which the DTC set. Use of CRUISE REQUESTED and CRUISE displays can be monitored at the same time to aid in diagnosis an intermittent fault. Clear DTC and operate vehicle under the conditions in which the DTC set.

DTC P1554 Schematic. Scheme 18

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check if DTC P1520 or P1810 is also present. If any of the DTC(s) are present, diagnose affected DTC(s) first. If DTC(s) are not present, go to next step.
3. Verify if transaxle was shifted into Park or Neutral while cruise control was engaged. If transaxle was shifted out of a drive gear, causing DTC to set, go to next step. If transaxle was not shifted out of a drive gear, see DIAGNOSTIC AIDS.
4. Clear DTC. Explain to vehicle operator that shifting transaxle out of a drive gear while cruise control is engaged will set DTC.

Shifting into Neutral while cruise control is engaged will set this DTC. If this DTC was not induced by vehicle operator, use FAILURE REC on scan tool to compare both the TRANS RANGE and PNP displays to verify that operator did not induce DTC. Also, compare both displays to see if transaxle pressure switch circuit may have an intermittent fault. Clear DTC and operate vehicle under the conditions in which the DTC set.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check if DTC P0503 is also present. If DTC P0503 is present, diagnose affected DTC first. If DTC P0503 is not present, go to next step.
3. Verify if DTC was set by wheelspin due to icy, wet or slippery conditions. If road conditions caused DTC to set, go to next step. If not, fault is not present. See DIAGNOSTIC AIDS.
4. Clear DTC. Explain to vehicle operator what caused DTC to set.

Use of the FAILURE REC on scan tool can help diagnose intermittent problems, by displaying how long ago and the conditions under which the DTC set. Clear DTC and operate vehicle under the conditions in which DTC was set.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Verify if DTC was set by wheelspin due to icy, wet or slippery conditions. If road conditions caused DTC to set, go to step 4). If not, go to next step.
3. Check for mechanical problems, such as transaxle slippage. Repair as necessary. If a mechanical problem is not present, see DIAGNOSTIC AIDS.
4. Clear DTC. Explain to vehicle operator what caused DTC to set.

Use of the FAILURE REC on scan tool can help diagnose intermittent problems, by displaying how long ago and the conditions under which the DTC set. Clear DTC and operate vehicle under the conditions in which DTC was set.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check if any traction control related DTC(s) are present. If DTC(s) are present, diagnose affected DTC(s) first. If other DTC(s) are not present, go to next step.
3. Since this DTC was caused most likely by wheel spin due to icy, wet or slippery road conditions, check with vehicle operator when DTC was set. If road condition caused DTC to set, go to next step. If road condition did not cause DTC to set, fault is not present. See DIAGNOSTIC AIDS.
4. Explain to vehicle operator the system operation. Clear DTC.

Use of the FAILURE REC. on scan tool can help diagnose intermittent problems, by displaying how long ago and the conditions under which the DTC set. Clear DTC and operate vehicle under the conditions in which it set, if fault condition is suspected.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check for ABS/TCS related DTC(s). If DTC(s) are present, diagnose affected DTC(s) first. If other DTC(s) are not present, go to next step.
3. Check for intermittent terminal connection, intermittent open or short to the desired torque PWM input circuit between PCM connector C2 and EBTCM harness connector terminals. Repair as necessary. If circuit or terminal is okay, fault is not present. See DIAGNOSTIC AIDS.

If no fault is present, diagnose ABS/TCS system using appropriate ANTI-LOCK BRAKE SYSTEM article in the BRAKES section.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check of DTC P1602 is also present. If DTC P1602 is present, diagnose this DTC first. If DTC P1602 is not present, see DIAGNOSTIC AIDS.

DTC P1574 indicates that the stop light switch signal to the EBTCM or the EBTCM's ability to send the stop light switch signal to the PCM has failed. For further diagnosis refer to ABS/TCS DTC 74. See appropriate ANTI-LOCK BRAKE SYSTEM article in the BRAKES section.

Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to appropriate ANTI-LOCK BRAKE SYSTEM article in the BRAKES section for diagnosis of extended travel brake switch using DTC 72.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Since this DTC will set when the vehicle is shifted into Drive/Reverse under possibly damaging conditions, check with vehicle operator to verify under which condition the DTC set. If vehicle operator actions caused this DTC to set, fault is not present. See DIAGNOSTIC AIDS. If vehicle operator did not cause DTC to set, go to next step.
3. Check for proper adjustment of transaxle range switch and for poor terminal contact at switch and the PCM. Repair as necessary. If adjustment or terminal contact is okay, fault is not present. See DIAGNOSTIC AIDS.

If driver's action caused the DTC to set, clear DTC and inform driver of proper shift procedure.

Use FAILURE REC. information on scan tool to help diagnose an intermittent problem. Manipulate wiring harness while watching scan tool display, looking of an open or short in circuit.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. If complaint is engine stalling, go to next step. If engine is not stalling, fault is not present. See DIAGNOSTIC AIDS.
3. Turn ignition on. Using scan tool, check if other DTC(s) are present. If other DTC(s) are present, diagnose affected DTC(s) first. If no other DTC(s) are present, go to next step.
4. Select DATA LIST under SPECIFIC ENGINE and select DTC P1599. Note MAP sensor display taken at the time this DTC was set. If scan tool displayed value is greater than 95 kPa, go to next step. If scan tool displayed value is 95 kPa or less, see TESTS W/O CODES article.
5. Stalling can be caused by either fuel system, idle speed control, emissions related components or faulty wiring and connections. Perform fuel system check. See BASIC TESTING article. Repair as necessary. If fault is not found or if related systems are okay, go to next step.
6. Check for TCC that is improperly applied due to grounded TCC solenoid circuit or by transaxle hydraulic problems. Check ignition switch circuits for intermittent open to PCM or IC module. Wiggle ignition key while driving to check for intermittent ignition switch connection or switch out of adjustment. Check PCM and IC module ground. Check for intermittent injector circuit operation. Check fuel pump ground for loose or poor connection. Repair as necessary. If repair was not necessary, see DIAGNOSTIC AIDS.

Use scan tool snapshot data taken of DTC P1599 to determine cause of stalling condition.

Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, diagnose ABS/TCS system. See appropriate ANTI-LOCK BRAKE SYSTEM article in the BRAKES section.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, diagnose air bag (SIR) system. See appropriate AIR BAG RESTRAINT SYSTEM article in the ACCESSORIES/SAFETY EQUIPMENT section.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, diagnose IPC. See appropriate INSTRUMENT PANEL article in the ACCESSORIES/SAFETY EQUIPMENT section.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, diagnose Electronic Climate Control (ECC) or A/C-heater system.

EEPROM is a data storage unit which can save critical data even battery power is removed. This is used by the PCM to store TP sensor idle learned values, transaxle adapt values, transaxle oil life index and cruise control lash/learn.

The EEPROM has several locations available to store this information. If PCM detects a problem in one location of the EEPROM, it will store the data in another location. If PCM runs out of good locations in the EEPROM to store data, it will set the DTC.

The PCM stores the same data in its Keep Alive Memory so that even if the EEPROM is bad and DTC is set, the operator will not notice any difference in vehicle operation. Even after DTC sets, the PCM will continue to look for good locations in the EEPROM in which to store data and if it finds one, DTC will become a history code. EEPROM is soldered into the PCM and cannot be serviced. If a current DTC P1621 is set, PCM must be replaced.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool in DTC INFO mode, select FAIL THIS IGN. If this DTC failed this ignition cycle, go to step 4). If this DTC did not fail in this ignition cycle, go to next step.
3. Clear DTC. Cycle ignition on and off several times slowly (ignition on for 10 seconds then ignition off for 30 seconds). In DTC INFO mode on scan tool, select TEST FAIL SCC. If this DTC failed since it was cleared, go to next step. If this DTC has not failed since it was cleared, fault is not present.
4. Replace PCM. Program replacement PCM using required equipment.

This DTC is an indication that the fuel enable input to the PCM has failed in a given cycle. the PASS-Key(R) system enables engine operation by allowing the starter to engage and issuing a fuel enable signal to the PCM. If a failure is present at the end of the fuel decision point, a no start condition can be caused. Additionally, the PCM will not disable fuel injection after is has been enabled within a given ignition cycle to prevent stalling as a result of PASS-Key(R) system failure.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Attempt to start engine. If engine cranks, go to next step. If engine does not crank, check starting system. See appropriate STARTING & CHARGING SYSTEMS article in the ELECTRICAL section.
3. Turn ignition off. Disconnect PASS-Key(R) module harness connector. Turn ignition on. Using DVOM, check voltage between ground and PASS-Key module fuel enable input circuit at harness connector terminal. If voltage is 2-6 volts, go to next step. If voltage is not as specified, go to step 6).
4. Turn ignition off. Reconnect PASS-Key(R) module harness connector. Turn ignition on. Measure DC frequency between PASS-Key(R) module fuel enable input circuit terminal and ground. If frequency reading is 40-60 Hz, go to next step. If frequency reading is not 40-60 Hz, go to step 8).
5. Clear DTC. Attempt to start engine. If engine starts, fault is not present. If engine does not start, go to step 12).
6. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Using DVOM, check resistance of PASS-Key(R) fuel enable circuit between PCM harness connector C1 and PASS-Key(R) module harness connector terminals. If resistance is 5 ohms or less, go to next step. If resistance is greater than 5 ohms, go to step 10).
7. Check resistance between ground and PASS-Key(R) fuel enable input circuit at PCM harness connector terminal. If resistance is greater than 10,000 ohms, go to step 12). If resistance is less than 10,000 ohms, go to step 11).
8. Check terminal contact at PASS-Key(R) module harness connector. Repair as necessary. If terminal contacts are okay, go to next step.
9. Replace PASS-Key(R) module.
10. Repair open in fuel enable input circuit.
11. Repair short to ground in fuel enable input circuit.
12. Check terminal contact at PCM harness connector C1. Repair as necessary. If terminal contact is okay, go to next step.
13. Replace PCM. Program replacement PCM using required equipment.

An intermittent setting of DTC P1626 could be caused by an intermittent open/short to ground or short to voltage in fuel enable input circuit.

An intermittent no-start could be caused by loss of power or ground to the PASS-Key(R) module. Since the module samples the ignition key resistor pellet only once per ignition cycle (at key on), faults of the PASS-Key(R) system cannot cause a stalling problem.

DTC P1626 Schematic. Scheme 19

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check if DTC P1634 is also present. If DTC P1634 is also present, diagnose this DTC first. If DTC P1634 is not present, go to next step.
3. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Using DVOM, check voltage between ground and ignition feed circuit at PCM harness connector C2, terminal No. 37. Using scan tool, note and write down IGNITION 1 voltage reading. If DVOM and scan tool voltage readings are within .5 volt of each other, go to next step. If DVOM and scan tool voltage reading is greater than .5 volt of each other, go to step 5).
4. Turn ignition off. Reconnect PCM harness connector C2. Turn ignition on. Using scan tool, clear DTC. Start and idle engine. After 10 seconds in DTC INFO mode, select FAIL THIS IGN. If DTC failed in this ignition cycle, go to step 6). If DTC did not fail in this ignition cycle, fault is not present. See DIAGNOSTIC AIDS.
5. Repair open in ignition feed circuit between PCM harness connector and splice.
6. Check terminal contact at PCM harness connector C2, terminal No. 37. Repair as necessary. If terminal contact is okay, go to next step.
7. Replace PCM. Program replacement PCM using required equipment.

If ignition supplement to the PCM is lost, the engine will still run, but some outputs may not function. If Ignition 1 voltage is lost or drops to less than 5.5 volts, engine will not run and DTC should set.

If this DTC is intermittent, check terminal contact at PCM and condition of splice for an intermittent open circuit.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Using scan tool, check if DTC P0560 is also present. If DTC P0560 is also present, diagnose this DTC first. If DTC P0560 is not present, go to next step.
3. Note both the IGNITION 0 and IGNITION 1 displays on scan tool. Compare both voltage readings. If readings are within .5 volt, go to next step. If readings are not within .5 volt, go to step 5).
4. Clear DTC using scan tool. Start and idle engine. After 10 seconds in DTC INFO mode, select FAIL THIS IGN. If DTC failed this ignition cycle, go to step 6). If DTC did not fail this ignition cycle, fault is not present. See DIAGNOSTIC AIDS.
5. Check for an open circuit or poor splice connection on the circuit that has low voltage. Replace as necessary. If circuit is okay, fault is not present. See DIAGNOSTIC AIDS.
6. Check terminal contact at PCM harness connector C1, terminals No. 18 and 19. Repair as necessary. If terminal contact is okay, go to next step.
7. Replace PCM. Program replacement PCM using required equipment.

If Ignition 0 to the PCM is lost, the engine will still run, but some outputs may not function. If Ignition 1 voltage is lost or drops to less than 5.5 volts, engine will not run and DTC should set.

If this DTC is intermittent, check terminal contact at PCM and condition of splice for an intermittent open circuit.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Ensure battery is fully charged. Disconnect generator harness connector. Start engine. Using DVOM, check voltage between ground and generator harness connector terminal "L". If voltage reading is 10 volts or greater, go to step 9). If voltage reading is less than 10 volts, go to next step.
3. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Using DVOM, check resistance between ground and generator harness connector terminal "L". If resistance is 10,000 ohms or greater, go to next step. If resistance is less than 10,000 ohms, go to step 5).
4. Check resistance between generator harness connector terminal "L" and PCM harness connector C1 terminal No. 75. If resistance is 5 ohms or less, go to step 7). If resistance is greater than 5 ohms, go to step 6).
5. Repair short to ground in generator "L" terminal feedback circuit.
6. Repair open or high resistance in generator "L" terminal feedback circuit.
7. Check terminal contact at generator "L" terminal feedback circuit terminal of PCM harness connector C1. Repair as necessary. If terminal contact is okay, go to next step.
8. Replace PCM. Program replacement PCM using required equipment.
9. Turn ignition off. Check record voltage between underhood battery positive junction block and ground. Check voltage between generator harness connector terminal "S" and ground. If voltage readings are within one volt of each other, go to step 11). If voltage readings are not within one volt of each other, go to next step.
10. Repair open or high resistance in circuit to battery temperature sensor or battery temperature sensor.
11. Repair or replace generator.

DTC P1637 and a low battery charge may be caused by a generator fault, such as a shorted output diode, malfunctioning regulator, open or shorted rotor, or open sense lead. This DTC will not set if generator "L" terminal circuit is shorted to voltage, but may cause a parasitic load on the battery with ignition off.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check of DTC P0560 is also present. If DTC P0560 is present, diagnose this DTC first. If this DTC is not present, go to next step.
3. Start and idle engine for 2 minutes. Using scan tool in DTC INFO mode, select FAIL THIS IGN. If this DTC failed in this ignition cycle, go to next step. If this DTC did not fail in this ignition cycle, fault is not present.
4. Turn ignition on, with engine off. In ENGINE 1 mode, note GEN F TERMINAL display on scan tool. If duty cycle reading on scan tool is zero percent or greater, go to next step. If scan tool reading is zero percent, go to step 6).
5. If duty cycle is less than 5 percent, diagnose generator. See appropriate STARTING & CHARGING SYSTEM article in the ELECTRICAL section. If duty cycle is greater than 5 percent, go to step 12).
6. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Turn ignition on. Using DVOM, check voltage between ground and generator "F" terminal feedback circuit at PCM harness connector C1 terminal. If voltage is .1 volt or greater, go to step 9). If voltage is less than .1 volt, go to next step.
7. Check resistance between ground and generator "F" terminal feedback circuit on PCM harness connector C1 terminal. If resistance is less than 10,000 ohms, go to step 10). If resistance is greater than 10,000 ohms, go to next step.
8. Check generator "F" terminal feedback circuit resistance between PCM and generator harness connector terminals. If resistance is 5 ohms or less, diagnose generator. See appropriate STARTING & CHARGING SYSTEM article in the ELECTRICAL section. If resistance is greater than 5 ohms, go to step 11).
9. Replace short to voltage in generator "F" terminal feedback circuit.
10. Repair short to ground in generator "F" terminal feedback circuit.
11. Repair open in generator "F" terminal feedback circuit.
12. Check terminal contact at generator harness connector. Repair as necessary. If terminal connector is okay, go to next step.
13. Check terminal contact at PCM harness connector C1. Repair as necessary. If terminal contact is okay, go to next step.
14. Replace PCM. Program replacement PCM using required equipment.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Start and idle engine. Using scan tool, select ENGINE 1 mode and note IGNITION 1 display. Compare this voltage reading with voltage reading displayed by vehicle message center. If PCM and vehicle voltage readings differ by greater than .5 volt, go to next step. If PCM and vehicle voltage readings is within .5 volt of each other, fault is not present. See DIAGNOSTIC AIDS.
3. Using DVOM, check voltage between ground and PCM fuse. If PCM fuse voltage and scan tool displayed voltage reading difference is greater than .5 volt, go to next step. If PCM fuse voltage and scan tool displayed voltage reading is within .5 volt of each other, check charging system. See appropriate CHARGING & STARTING SYSTEM article in the ELECTRICAL section.
4. Check for high resistance is ignition feed circuits to PCM. Repair as necessary. If circuits are okay, go to next step.
5. Check terminal contacts at PCM harness connector C1. Repair as necessary. If terminal contacts are okay, go to next step.
6. Replace PCM. Program replacement PCM using required equipment.

An overvoltage at ODM No. 1 will also trigger DTC P0563. Use DTC P0563 to diagnose if vehicle voltage is actually too high. A loose or faulty connection at generator "L" terminal may cause DTC P1640 to set intermittently.

PCM contains Output Driver Modules (ODM) that provides 7 switchable ground outputs for operating solenoids, relays, indicator lights, and other devices. Each of these ground outputs has fault lines that feed back to the PCM's microprocessor. When the output is off, the output driver should receive the 12 volts fed to the solenoid, relay, etc. When the output is on, it should receive zero volts, since it is grounding the output. when PCM sees zero volts when the output is off or 12 volts when the output is on, it sets a fault line low. DTC P1641 is used to monitor the fault line of the SERVICE ENGINE SOON light.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Check if MIL illuminates after 5 seconds. If MIL illuminates, go to next step. If MIL does not illuminate, go to step 4).
3. Using scan tool, enter OUTPUT TESTS then select MIL. Command MIL off. If MIL turns off, fault is not present. See DIAGNOSTIC AIDS. If MIL does not turn off, go to step 8).
4. Select ENGINE 3 mode and note MALFUNCTION IND LAMP DRIVER display on scan tool. If scan tool display indicates OK, go to next step. If scan tool display does not indicate OK, go to step 6).
5. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Remove IP cluster fuse. Turn ignition on. Using DVOM, check voltage between ground and MIL signal circuit at PCM harness connector C2 terminal. If voltage reading is .5 volt or greater, go to step 9). If voltage reading is not .5 volt or more, go to step 13).
6. Reinstall IP cluster fuse. Using a jumper wire, jumper MIL signal circuit at PCM harness connector C2 to ground. If MIL illuminates, go to step 13). If MIL does not illuminate, go to next step.
7. Check condition of IP fuse. If fuse is faulty, go to step 10). If fuse is okay, go to step 13).
8. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. If MIL illuminates, go to step 12). If MIL does not illuminate, go to step 13).
9. Repair short to voltage in MIL signal circuit.
10. Repair short to ground in circuit between MIL and fuse block.
11. Repair open in MIL circuit from fuse block to PCM. Check for faulty MIL bulb.
12. Replace short to ground in MIL circuit between MIL bulb and PCM.
13. Check terminal contact at PCM harness connector C2. Repair as necessary. If terminal connector is okay, go to next step.
14. Replace PCM. Program replacement PCM using required equipment.

Use the FAILURE REC as indicated on scan tool to aid in diagnosing an intermittent fault. Use data captured when DTC was set, to determine if an open or shorted condition caused the DTC to set. Ensure no other DTC(s) are present, commanding MIL to illuminate.

DTC P1641 Schematic. Scheme 20

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, select ENGINE 3 mode and note VEHICLE SPEED DRIVER display. If scan tool display indicates OK, go to next step. If scan tool display does not indicate OK, go to step 5).
3. Raise and support drive wheels. Start engine. Spin wheels for about 2 seconds to generate a vehicle speed signal. In DTC INFO mode, select FAIL THIS IGN on scan tool. If scan tool indicates that DTC failed in this ignition cycle, go to next step. If scan tool does not indicate that DTC failed in this ignition cycle, fault is not present. See DIAGNOSTIC AIDS.
4. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Using DVOM, check voltage between ground and vehicle speed output signal circuit at PCM harness connector C2 terminal. If voltage reading is 10 volts or greater, go to step 7). If voltage reading is less than 10 volts, go to next step.
5. Repair open or short in vehicle speed output circuit between PCM and IPC, and cruise control module and RAC module. Repair as necessary.
6. Repair short to voltage in vehicle speed output circuit between PCM and IPC, and cruise control module and RAC module. Repair as necessary.
7. Check terminal contact at PCM harness connector C2. Repair as necessary. If terminal contact is okay, go to next step.
8. Replace PCM. Program replacement PCM using required equipment.

Use the FAILURE REC indicated on scan tool to aid in diagnosing an intermittent fault. Use the data captured when the DTC was set to determine the conditions under which the DTC set.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool in ENGINE 3 mode, observe DELIVERED TORQUE DRIVER display. If scan tool display indicates OK, fault is not present. See DIAGNOSTIC AIDS. If scan tool display does not indicate OK, go to next step.
3. If scan tool display indicates OPEN, go to next step. If scan tool display does not indicate OPEN, go to step 6).
4. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Using DVOM, check voltage between ground and delivered torque PWM output circuit at PCM harness connector C2 terminal. If voltage reading is 10 volts or greater, go to step 13). If voltage reading is less than 10 volts, go to next step.
5. Turn ignition to LOCK position. Disconnect EBTCM harness connector. Check resistance of delivered torque PWM output circuit between PCM harness connector and EBTCM harness connector terminals. If resistance is 5 ohms or less, go to step 12). if resistance is greater than 5 ohms, go to step 9).
6. Turn ignition to LOCK position. Disconnect EBTCM harness connector. Turn ignition on. If scan tool display indicates OPEN, go to step 12). If scan tool display does not indicate OPEN, go to next step.
7. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Using DVOM, check resistance between ground and delivered torque PWM output circuit at PCM harness connector C2 terminal. If voltage is greater than .5 volt, go to step 10). If voltage is less than .5 volt, go to next step.
8. Using DVOM, check resistance between ground and delivered torque PWM output circuit at PCM harness connector C2 terminal. If resistance is 10,000 ohms or greater, go to step 13). If resistance is less than 10,000 ohms, go to step 11).
9. Repair open in delivered torque PWM output circuit.
10. Repair short to voltage in delivered torque PWM output circuit.
11. Repair short to ground in delivered torque PWM output circuit.
12. Fault is in the EBTCM system. Diagnose EBTCM. See appropriate ANTI-LOCK BRAKE SYSTEM article in the BRAKES section. If fault is not found in EBTCM system, check for faulty terminal contact to EBTCM. If terminal contact is okay, replace EBTCM.
13. Check terminal contact at PCM harness connector C2. Repair as necessary. If terminal contact is okay, go to next step.
14. Replace PCM. Program replacement PCM using required equipment.

Check for an intermittent poor connection at both the PCM and EBTCM. Also, check for open or short in delivered torque PWM output circuit between EBTCM and PCM.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, check if DTC P1633 or P1644 is present. If any of the DTC is present, diagnose affected DTC first. If DTC P1653 or P1644 is not present, go to next step.
3. If DTC P0102, P0401, P0550, P0753, P0758, P1406 or P1860 is also present, go to step 10). If these DTC(s) are not present, go to next step.
4. Using scan tool, select ENGINE 3 and note EVAP PURGE SOL. DRIVER display. If scan tool display indicates OK, go to next step. If scan tool display does not indicate OK, go to step 6).
5. Start and idle engine. Select OUTPUT TESTS and select EVAP PURGE. Command EVAP purge solenoid on (open) for at least 2 seconds. Note EVAP PURGE SOL. DRIVER display. If scan tool display indicates OK, fault is not present. See DIAGNOSTIC AIDS. If scan tool display does not indicate OK, go to step 9).
6. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Using DVOM, check voltage between ground and EVAP purge solenoid circuit at PCM harness connector C2 terminal. If voltage reading is 10 volts or greater, go to step 15). If voltage reading is less than 10 volts, go to next step.
7. Disconnect EVAP purge solenoid harness connector. Check voltage between ground and EVAP purge solenoid ignition circuit harness connector terminal. If voltage reading is 10 volts or greater, go to next step. If voltage reading is less than 10 volts, go to step 11).
8. Using jumper wire, jumper EVAP purge solenoid harness connector terminals together. Check voltage between ground and EVAP purge solenoid circuit at PCM harness connector terminal. If voltage reading is 10 volts or greater, go to step 12). If voltage reading is less than 10 volts, go to step 13).
9. Turn ignition off. Disconnect EVAP purge solenoid harness connector. Turn ignition on. Using DVOM, check voltage between ground and EVAP purge solenoid signal circuit harness connector terminal. If voltage is .5 volt or greater, go to step 14). If not, go to step 12).
10. Repair open or short in EVAP purge solenoid ignition circuit. Also, check for faulty fuse. Repair as necessary.
11. Repair open in EVAP purge solenoid ignition circuit and splice.
12. Replace EVAP purge solenoid.
13. Repair open in circuit between EVAP purge solenoid and PCM.
14. Repair short to voltage in circuit between EVAP purge solenoid and PCM.
15. Check terminal contact at PCM harness connector terminal C2. Repair as necessary. If terminal contact is okay, go to next step.
16. Replace PCM. Program replacement PCM using required equipment.

Use the FAILURE REC. on scan tool to aid in diagnosing an intermittent fault. Use the data captured when the DTC set, to determine if an open or shorted condition caused the DTC to set.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Start and idle engine. Using scan tool, select ENGINE 1 mode and note IGNITION 1 display. Compare this voltage reading with voltage reading displayed by vehicle message center. If PCM and vehicle voltage readings differ by greater than .5 volt, go to next step. If PCM and vehicle voltage readings are within .5 volt of each other, fault is not present. See DIAGNOSTIC AIDS.
3. Using DVOM, check voltage between ground and PCM fuse. If PCM fuse voltage and scan tool displayed voltage reading difference is greater than .5 volt, go to next step. If PCM fuse voltage and scan tool displayed voltage reading are within .5 volt of each other, check charging system. See appropriate STARTING & CHARGING SYSTEMS article in the ELECTRICAL section.
4. Check for high resistance in ignition feed circuits to PCM. Repair as necessary. If circuits are okay, go to next step.
5. Check terminal contacts at PCM harness connector C1. Repair as necessary. If terminal contacts are okay, go to next step.
6. Replace PCM. Program replacement PCM using required equipment.

An overvoltage at ODM No. 2 will also trigger DTC P0563. Use DTC P0563 to diagnose if vehicle voltage is actually too high. A loose or faulty connection at generator "L" terminal may cause DTC P1650 to set intermittently.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, select ENGINE 3 mode and note CRUISE ENABLE DRIVER display. If scan tool display indicates OK, go to next step. If scan tool display does not indicate OK, go to step 6).
3. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Turn ignition on. Using DVOM, check voltage between ground and cruise inhibit output circuit at PCM harness connector C1 terminal. If voltage reading is 10 volts or greater, fault is not present. See DIAGNOSTIC AIDS. If voltage reading is less than 10 volts, go to next step.
4. Turn ignition off. Disconnect cruise control module harness connector. Check resistance between ground and cruise control module harness connector terminal "H". If resistance is 5 ohms or less, go to step 8). If resistance is greater than 5 ohms, go to step 9).
5. Check resistance of cruise inhibit output circuit between cruise control module harness connector and PCM harness connector terminals. If resistance is 5 ohms or less, go to step 7). If resistance is greater than 5 ohms, go to step 9).
6. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C1. Disconnect cruise control module. Turn ignition on. Using DVOM, check voltage between ground and cruise inhibit output circuit at PCM harness connector C1 terminal. If voltage reading is 10 volts or greater, go to step 10). If voltage reading is less than 10 volts, go to step 14).
7. Turn ignition on. Check voltage to ground at cruise control module terminal "F". If voltage reading is 10 volts or greater, go to step 12). If voltage reading is 10 volts or less, go to step 11).
8. Repair short to ground in cruise inhibit output circuit.
9. Repair open in cruise inhibit output circuit.
10. Repair short to voltage in cruise inhibit output circuit.
11. Repair open or short to ground (if fuse is blown) in ignition circuit to TCC brake switch and to cruise control module.
12. Check terminal contact at cruise control module. Repair as necessary. If terminal contact is okay, go to next step.
13. Replace cruise control module.
14. Check terminal contact at PCM. Repair as necessary. If terminal contact is okay, go to next step.
15. Replace PCM. Program replacement PCM using required equipment. Go to next step.

Use the FAILURE REC. to aid in diagnosing an intermittent fault. Use the data captured when the DTC set to determine if an open or shorted condition caused the DTC to set.

PCM contains Output Driver Modules (ODM) that provides 4 switchable ground outputs for operating solenoids, relays, indicator lights, and other devices. Each of these ground outputs has fault lines that feed back to the PCM's microprocessor. When the output is off, the output driver should receive the 12 volts fed to the solenoid, relay, etc. When the output is on, it should receive zero volts, since it is grounding the output. when PCM sees zero volts when the output is off or 12 volts when the output is on, it sets a fault line low.

DTC P1645 is used to monitor the fault line of the cooling fan control relay output and the starter inhibit output.

1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
2. Turn ignition on. Turn off A/C. Using scan tool in MISC TESTS, select OUTPUT TESTS then select FAN RELAYS. Command all relays off and note QUAD DRIVER 1. If scan tool display indicates OK, go to next step. If scan tool display does not indicate OK, go to step 9).
3. Command all relays off and note QUAD DRIVER 1 display on scan tool. If scan tool display indicates OK, go to next step. If scan tool display does not indicate OK, go to step 6).
4. Turn ignition on, with engine off. Command STARTER INHIBIT on. If QUAD DRIVER 1 on scan tool display indicates OK, go to next step. If scan tool display does not indicate OK, go to step 20).
5. If cooling operation fault is suspected, diagnose cooling fan. See SYSTEM/COMPONENT TESTS article. If cooling fan is operating properly, fault it not present.
6. While noting QUAD DRIVER 1 display, command FAN RELAY 1 on. If scan tool display indicates OK, go to step 8). If scan tool display does not indicate OK, go to next step.
7. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Remove cooling fan relay No. 1 (low speed). Turn ignition on. Using DVOM, check voltage between ground and cooling fan low speed control circuit at PCM harness connector C2 terminal. If voltage reading is .5 volt or less, go to step 27). If voltage reading is greater than .5 volt, go to step 18).
8. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Remove cooling fan relays No. 2 and 3. Turn ignition on. Using DVOM, check voltage between ground and cooling fan high speed control circuit at PCM harness connector C2. If voltage reading is .5 volt or less, go to step 27). If voltage reading is greater than .5 volt, go to step 19).
9. In ENGINE 3 data list mode, note PASSKEY STARTER display on scan tool. If scan tool display indicates ENABLED, go to next step. If scan tool display does not indicate ENABLED, go to step 21).
10. With all relays still commanded off, observe operation of both cooling fans. If either fan operates, go to next step. If either fan does not operate, go to step 12).
11. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Using DVOM, check voltage between ground and cooling fan low speed control circuit at PCM harness connector C2. If voltage reading is 10 volts or greater, go to step 16). If voltage reading is less than 10 volts, go to step 17).
12. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Using DVOM, check voltage between ground and cooling fan high and low speed control circuits at PCM harness connector C2. If voltage reading on both terminals is 10 volts or greater, go to step 27). If voltage reading on both terminals is less than 10 volts, go to next step.
13. If voltage measured is low on both terminals, go to step 15). If voltage measured is low only on one of the terminals, go to next step.
14. Repair open circuit or replace open cooling fan relay for circuit that measured low in step 9).
15. Repair cause of no voltage to both circuits. Replace fuse, if faulty. A no voltage to both circuits can be caused by, open in both the high and low cooling fan control circuits, open in ignition circuit to both relays, short to ground in ignition circuit to both relays (fuse blown), short fan relay(s), short to ground in ignition circuit to A/C compressor relay (fuse blown) or shorted A/C compressor relay (blown fuse).
16. Repair short to ground in cooling fan high speed control circuit.
17. Repair short to ground in cooling fan low speed control circuit.
18. Repair short to voltage in cooling fan low speed control circuit.
19. Repair short to voltage in cooling fan high speed control circuit.
20. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2 and PASS-Key(R) module harness connector. Turn ignition on. Using DVOM, check voltage between ground and starter inhibit output circuit at PCM harness connector C2. If voltage reading is greater than .5 volt, go to step 24). If voltage reading is less than .5 volt, go to step 27).
21. Store fluid life index as indicated on scan tool. Turn ignition off and wait 30 seconds, then disconnect PCM harness connector C2. Turn ignition on. Using DVOM, check voltage between ground and starter inhibit output circuit at PCM harness connector C2. If voltage reading is 10 volts or greater, go to step 27). If voltage reading less than 10 volts, go to next step.
22. Turn ignition off. Disconnect PASS-Key(R) module harness connector. Check resistance between ground and starter inhibit output circuit at PCM harness connector C2. If resistance is 10,000 ohms or greater, go to next step. If resistance is greater than 10,000 ohms, go to step 25).
23. Check resistance on starter inhibit output circuit between PCM harness connector C2 and PASS-Key(R) harness connector terminals. If resistance is less than 5 ohms, fault is not present. Diagnose anti-theft deterrent system. See appropriate ANTI-THEFT SYSTEM article in the ACCESSORIES/SAFETY EQUIPMENT section. If resistance is greater than 5 ohms, go to step 26).
24. Repair short to voltage in starter inhibit output circuit.
25. Repair short to ground in starter inhibit output circuit.
26. Repair open in starter inhibit output circuit.
27. Check terminal contact at PCM. Repair as necessary. If terminal contact is okay, go to next step.
28. Replace PCM. Program replacement PCM using required equipment.

DTC P1660 Schematic. Scheme 21