Engine Controls - Tests W/codes - 3.1l Chevrolet Malibu V

INTRODUCTION

Most engine control problems are the result of mechanical breakdowns, poor electrical connections or damaged vacuum hoses. Before considering the computer system as a possible cause of problems, perform basic diagnostic procedures in the BASIC TESTING - 3.1L article. Failure to do so may result in lost diagnostic time.

If no faults were found while performing basic diagnostic procedures, proceed with DIAGNOSTIC PROCEDURE under SELF-DIAGNOSTIC SYSTEM. If no fault codes are present and driveability problems exist, proceed to TESTS W/O CODES - 3.1L article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.). If only intermittent codes are present, see INTERMITTENTS in TESTS W/O CODES - 3.1L article.

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 cluster. 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.

Hard Failures

Most hard failures cause MIL to illuminate and remain on until malfunction is repaired. If MIL comes on and remains on (light may flash) during vehicle operation, cause of malfunction must be determined. See DIAGNOSTIC PROCEDURE .

If a sensor fails, PCM/VCM will use a substitute value in its calculations to continue engine operation. In this condition, vehicle is functional, but it will most likely display degraded driveability.

Intermittent Failures

Intermittent failures cause MIL to flicker or glow and go out about 10 seconds after intermittent fault goes away. Corresponding DTC, however, will be retained in PCM/VCM memory. If related fault does not reoccur within 50 engine starts, trouble code will be erased from control module memory. Intermittent failures may be caused by sensor, connector or wiring related problems. See INTERMITTENTS in TESTS W/O CODES - 3.1L article.

Note. OBD II vehicles have options available in the scan tool DTC mode to display enhanced information available. However, to fully utilize information and procedures requires the use of a Tech 1 or 2 scan tool. See scan tool operator's manual for additional information.

The following are Tech 1 or 2 scan tool sub-menus in the DTC INFO and SPECIFIC DTC modes

DTC INFO MODE

Used to search for a specific type of stored DTC information. There are 7 choices in this mode. Technician may be instructed to test DTC(s) in a certain manner. Follow the affected DTC test procedures. To get complete description of any status, hit ENTER key before pressing the desired F-key.

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.

FAIL THIS IGN.

This selection will display all DTCs that have failed during the present ignition cycle.

HISTORY

This selection will display only DTC(s) that are stored in the control module's history memory. It will not type "B" DTCs. It will display all type "A" and type "B" DTCs that have the MIL illuminated and have failed within the last 40 warm-up cycles. It will also display type "C" DTCs that have failed within the 40 warm-up cycles.

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.

MIL REQUEST

This selection will display only DTCs that are requesting the MIL. Type "C" DTCs cannot be displayed using this option. This selection will report type "B" DTCs only after the MIL has been requested.

NOT RUN SCC

Not Run Since Code Clear option will display up to 33 DTCs that have not run since DTCs were last cleared. Since any displayed DTCs have not run, their condition (passing or failing) is unknown.

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.

FAILED SINCE CLEAR

This message indicates the DTC has failed at least once within the last 40 warm-up cycles since the last time DTCs were cleared.

NOT RUN SINCE CL.

Not Run Since Cleared message indicates that the selected diagnostic test has not run since the last time DTCs were cleared. Therefore, the diagnostic test status (passed or failed) is unknown. After DTCs are cleared, this message will continue to be displayed until the diagnostic test runs.

NOT RUN THIS IGN.

Not Run This Ignition message indicates the selected diagnostic test has not run this ignition cycle.

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. Powertrain On-Board Diagnostic (OBD) System Check must be performed before using specific DTC testing procedure. See «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) .
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»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__hard-or-intermittent-trouble-code-determination) . For diagnosing hard codes, proceed to appropriate DTC test. For diagnosing intermittent codes, proceed to INTERMITTENTS in TESTS W/O CODES - 3.1L article.
3. If no DTCs are present and a driveability problem exists, refer to SYMPTOMS in TESTS W/O CODES - 3.1L article. Doing so will help identify proper system or component to check in SYSTEM/COMPONENT TESTS - 3.1L article.
4. After necessary repairs are made, clear DTCs, verify vehicle will enter "closed loop" operation and ensure DTC does not reset.

POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK

Note. Tech 1 or 2 scan tool is required to perform OBD system check.

The OBD System Check determines

1. If Malfunction Indicator Light (MIL) operates.
2. If PCM is operating and can recognize a fault.
3. If any DTCs are stored.

After performing procedures in PRELIMINARY INSPECTION & ADJUSTMENTS, BASIC FUEL SYSTEM CHECKS and BASIC IGNITION SYSTEM CHECKS in BASIC TESTING - 3.1L article, this is the starting point for utilizing the self-diagnostic system for determining computer-related problems. After performing necessary tests as described in the diagnostic circuit check, if no codes are indicated and driveability problems still exist, see TESTS W/O CODES - 3.1L article and SCAN TOOL USAGE.

1. Turn ignition on with engine off. Observe Malfunction Indicator Light (MIL). If MIL illuminates, go to next step. If MIL does not illuminate, go to MIL INOPERATIVE.
2. Turn ignition off. Install scan tool and follow scan tool manufacturer's instructions to proceed with test. Turn ignition on. If scan tool displays PCM data, go to next step. If scan tool does not display PCM data, go to DLC DIAGNOSIS OR NO SCAN TOOL DATA.
3. Attempt to start engine. If engine starts and runs, go to next step. If engine does not start, or starts and dies, go to NO START DIAGNOSIS in BASIC TESTING - 3.1L article.
4. Using scan tool, observe DTC status on LAST TST FAIL function. If any DTC is stored, save freeze frame and fail record information using scan tool CAPTURE INFO feature. If a DTC is indicated as last test failed, diagnose affected DTC. If DTC is not indicated, go to next step.
5. Using scan tool, display DTC fail records. If a DTC fail record is stored, save freeze frame and fail record information using scan tool CAPTURE INFO feature. If a fail record is not stored, go to next step. If a fail record is stored, diagnose affected DTC.
6. Compare scan tool engine data with actual control system data values. If value is within limits, system is okay. If value is not within limits, go to SYSTEM/COMPONENT TESTS - 3.1L article.

MIL INOPERATIVE

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Attempt to start engine. If engine starts, go to next step. If engine does not start, go to step 6).
3. Check instrument cluster ignition feed fuse. If fuse is okay, go to next step. If fuses are blown, go to step 15).
4. Turn ignition on. Using a test light connected to ground, probe instrument cluster connector ignition feed circuit. See WIRING DIAGRAMS - 3.1L article. If test light illuminates, go to next step. If test light does not illuminate, go to step 12).
5. Turn ignition off. Disconnect PCM connector. Turn ignition on. Using a jumper wire connected to ground, jumper PCM connector MIL driver circuit. See WIRING DIAGRAMS - 3.1L article. If MIL illuminates, go to step 10). If MIL does not illuminate, go to step 11).
6. Check PCM ignition feed and battery feed fuses. If fuses are okay, go to next step. If fuses are blown, go to step 14).
7. Turn ignition off. Disconnect PCM connector. Turn ignition on. Using a test light connected to ground, probe PCM connector ignition feed circuit. See WIRING DIAGRAMS - 3.1L article. If test light illuminates, go to next step. If test light does not illuminate, go to step 13).
8. Using a test light connected to ground, probe PCM connector battery feed circuit. See WIRING DIAGRAMS - 3.1L article. If test light illuminates, go to next step. If test light does not illuminate, go to step 13).
9. Check for poor PCM ground or PCM ground connection. Repair as necessary. After repairs, perform OBD system check. If ground and ground connection are okay, go to next step.
10. Check for poor PCM connection. Repair as necessary. After repairs, perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . If connection is okay, go to step 16).
11. Check for open in MIL driver circuit. See WIRING DIAGRAMS - 3.1L article. Repair as necessary. After repairs, perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . If circuit is okay, go to step 17).
12. Repair open in instrument cluster ignition feed circuit. Repair as necessary. After repairs, perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) .
13. Locate and repair open in PCM battery feed circuit or PCM ignition feed circuit. Repair as necessary. After repairs, perform OBD system check.
14. Locate and repair short to ground in PCM battery feed circuit or PCM ignition feed circuit. Repair as necessary. After repairs, perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) .
15. Locate and repair short to ground in instrument cluster ignition feed circuit. Repair as necessary. After repairs, perform OBD system check.
16. Replace PCM. Perform PCM relearn procedures. After repairs, perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) .
17. Check for poor instrument cluster MIL driver circuit connection. Repair as necessary. After repairs, perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . If connection is okay, diagnose instrument cluster.

DLC DIAGNOSIS OR NO SCAN TOOL DATA

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Turn ignition on with engine off. Connect a test light between DLC battery feed circuit and ground circuit. See WIRING DIAGRAMS - 3.1L article. If test light illuminates, go to step 4). If test light does not illuminate, go to next step.
3. Using a test light connected to ground, probe DLC battery feed circuit. See WIRING DIAGRAMS - 3.1L article. If test light illuminates, go to step 9). If test light does not illuminate, go to step 10).
4. Turn ignition on with engine off. Using DVOM connected to ground, probe DLC class 2 serial data circuit. See WIRING DIAGRAMS - 3.1L article. DVOM should read zero volts. If voltage is as specified, go to next step. If voltage is not as specified, go to step 7).
5. Turn ignition off. Disconnect PCM connector. Turn ignition on with engine off. Using DVOM connected to battery voltage, probe DLC class 2 serial data circuit. See WIRING DIAGRAMS - 3.1L article. DVOM should read zero volts. If voltage is as specified, go to next step. If voltage is not as specified, go to step 8).
6. Check for open in class 2 serial data circuit between DLC and PCM. Repair as necessary. After repairs, perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . If circuit is okay, go to step 11).
7. Check for short to voltage in class 2 serial data circuit. Repair as necessary. After repairs, perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . If circuit is okay, go to step 11).
8. Locate and repair short to ground in class 2 serial data circuit. After repairs, perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) .
9. Locate and repair open in DLC ground circuits. After repairs, perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) .
10. Locate and repair open or short to ground in DLC battery feed circuit. After repairs, perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) .
11. Replace PCM. Perform PCM relearn procedures. After repairs, perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) .

READING TROUBLE CODES

Note. Use of Tech 1 or 2 scan tool is required to retrieve DTCs. Refer to user reference manual supplied with scan tool.

TROUBLE CODE DEFINITIONS

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)»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__clearing-diagnostic-trouble-codes-dtc) .
2. Apply parking brake, and place transmission in Neutral or Park. Block drive wheels, and start engine. MIL should go out. Operate warm engine at specified RPM for 2 minutes and note MIL.
3. If MIL illuminates, enter diagnostic mode. Read and record DTCs. This will reveal hard failure codes. Oxygen sensor related DTCs may require a road test to reset hard failure after DTCs were cleared.
4. If MIL does not illuminate, all stored DTCs were intermittent failures.

Note. DTCs will be recorded at various operating times. Some DTCs 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 ECM/PCM/VCM for at least 30 seconds or clear codes using a scan tool.

ECM/PCM/VCM LOCATION

On most models, ECM/PCM/VCM is located behind right or left side of dash, behind right or left kick panel, or on left or right side of engine compartment. For a more precise location, see COMPONENT LOCATIONS in SYSTEM/COMPONENT TESTS - 3.1L article.

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. For scan data values, refer to scan tool manufacturer owner's manual or compare values with a known-good component or vehicle.

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. See POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. 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. 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 ECM/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 setting 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.

SUMMARY

If no hard fault codes are present, driveability symptoms exist or intermittent DTC(s) exist, proceed to TESTS W/O CODES - 3.1L article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.

DIAGNOSTIC TROUBLE CODES

Note. Before clearing DTCs, perform procedures under POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . Record FREEZE FRAME and FAILURE RECORDS for reference during testing. Data will be erased when DTCs are cleared. If ECM/PCM/VCM is replaced, NEW ECM/PCM/VCM must be programmed using special manufacturer's equipment.

DTC P0101 - MAF SENSOR SYSTEM PERFORMANCE

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Circuit Description

Mass Airflow (MAF) sensor measures amount of air entering engine during a given time. PCM uses MAF sensor information for fuel delivery calculations. MAF sensor readings during acceleration are much higher than those during deceleration or idle.

PCM calculates what MAF sensor reading should be received from sensor under certain conditions using engine speed (RPM), throttle position, and barometric pressure parameters. When these test conditions are met, PCM will compare its calculated MAF value to actual value received from sensor. If difference is too great, DTC will set.

Conditions required to set DTC are

1. Engine running.
2. System voltage 9-16 volts.
3. Throttle steady and TP ANGLE less than 50 percent.
4. EGR DUTY CYCLE less than 50 percent.
5. EGR PINTLE POS less than 50 percent.
6. MAF signal frequency significantly higher or lower than predetermined value based on barometric pressure, throttle position and engine RPM
7. Conditions present for greater than 12 seconds.

Diagnostic Procedures

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Using scan tool, check for stored DTCs. If DTC P1374 or P1635 is also set, diagnose that DTC first. If DTC P1374 or P1635 is not set, go to next step.
3. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Select SPECIFIC DTC function then enter DTC P0101. If scan tool indicates FAILED THIS IGN, go to next step. If scan tool does not indicate FAILED THIS IGN, see DIAGNOSTIC AIDS.
4. DO NOT clear codes. Unplug MAF sensor. Attempt to start engine. If engine starts and continues to run, go to next step. If engine does not start or starts but stalls, go to step 6).
5. Ignition off. Reconnect MAF sensor connector. Start engine. Monitor MAF signal on scan tool. Slowly increase engine speed to 3000 RPM. If MAF sensor signal increases with engine RPM, go to step 7). If MAF sensor signal does not increase with engine RPM, go to next step.
6. Go to DTC P0108 to diagnose MAP sensor circuit. After repairs, go to step 20).
7. Turn ignition on. Ensure throttle is closed. Using scan tool, observe THROTTLE AT IDLE display. If scan tool indicates YES, go to next step. If scan tool does not indicate YES, go to DTC P0121 to diagnose DTC as necessary.
8. Turn ignition off. Disconnect MAF sensor connector. Turn ignition on, with engine off. Using DVOM, check voltage between ground and signal circuit at MAF harness connector. If voltage is about 5 volts, go to next step. If voltage is not about 5 volts, go to step 10).
9. Connect test light between ignition feed and ground circuit terminals at MAF sensor harness connector. If test light illuminates, go to step 13). If test light does not illuminate, go to step 12).
10. If voltage is less than 4.5 volts, go to step 14). If voltage is not less than 4.5 volts, go to next step.
11. Turn ignition off. Disconnect PCM connectors. Using DVOM, check voltage between ground and signal circuit terminal at MAF harness connector. If voltage is near zero volts, go to step 20). If voltage is not near zero volts, go to step 17).
12. Connect a test light between ground and ignition feed circuit terminal at MAF sensor harness connector. If test light illuminates, go to step 15). If test light does not illuminate, go to step 16).
13. Check for poor connection at MAF sensor connector. Repair as necessary. After repairs, go to step 20). If connector is okay, go to step 18).
14. Check MAF sensor signal circuit for excessive resistance between PCM and MAF sensor connectors. Check for excessive resistance in sensor ground circuit. Check for MAF signal circuit shorted to sensor ground circuit. Check for poor connection at PCM. Repair as necessary. After repairs, go to step 20). If circuits are okay, go to step 19).
15. Locate and repair open in MAF sensor ground circuit. After repair is completed, go to step 20).
16. Locate and repair open or excessive resistance in MAF sensor ignition feed circuit. After repair is completed, go to step 20).
17. Locate and repair short to voltage in MAF sensor signal circuit. After repair is completed, go to step 20).
18. Replace MAF sensor. After replacing sensor, go to step 20).
19. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
20. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for DTC P0101. If scan tool indicates FAILED THIS IGN, repeat step 3). If scan tool does not indicate FAILED THIS IGN, repair is complete.

Check for sticking throttle plate. Check for carbon build-up on throttle plate and throttle bore. Check TP sensor. See SYSTEM/COMPONENT TESTS - 3.1L article. Check for poor connection at PCM. Check for misrouted MAF sensor wiring harness. Ensure harness is not close to high-voltage components.

DTC P0102 - MAF SENSOR CIRCUIT LOW FREQUENCY

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Mass Airflow (MAF) sensor measures amount of air entering engine during a given time. PCM uses MAF sensor information for fuel delivery calculations. MAF sensor readings during acceleration are much higher than those during deceleration or idle.

PCM calculates what MAF sensor reading should be received from 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 actual value received from sensor.

Conditions required to set DTC are

1. Engine running.
2. TP sensor ANGLE is less than 50 percent.
3. System voltage is greater than 8 volts.
4. MAF signal frequency less than 1200 Hertz (Hz).
5. Listed conditions present for greater than 0.5 second, plus 130 crankshaft revolutions.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Start engine and allow it to idle. Using scan tool, select ENG 1 data list. Monitor MAF FREQUENCY display. If frequency is less than 1200 Hz, go to step 4). If frequency is not less than 1200 Hz, go to next step.
3. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Select SPECIFIC DTC function then enter DTC P0102. If scan tool indicates FAILED THIS IGN, go to next step. If scan tool does not indicate FAILED THIS IGN, see DIAGNOSTIC AIDS.
4. Check air leaks at MAF sensor, throttle body spacer, intake manifold, PCV, system EGR system, oil dipstick tube and oil filler cap. Repair as necessary. After repairs, go to step 14). If air leak is not found, go to next step.
5. Turn ignition off. Disconnect MAF sensor harness connector. Turn ignition on, with engine off. Using DVOM, check voltage between ground and signal circuit terminal at MAF sensor harness connector. If voltage is about 5 volts, go to next step. If voltage reading is not about 5 volts, go to step 9).
6. Connect a test light between ignition feed circuit and ground circuit terminals at MAF sensor harness connector. Observe test light. If test light illuminates, go to step 8). If test light does not illuminate, go to next step.
7. Connect a test light between ground and ignition feed circuit terminal at MAF sensor harness connector. If test light illuminates, go to step 10). If test light does not illuminate, go to step 11).
8. Check for poor connection at MAF sensor connector. Repair as necessary. After repairs, go to step 14). If connector is okay, go to step 12).
9. Check MAF sensor signal circuit between PCM and MAF sensor for an open, short to voltage or short to ground. Repair as necessary. After repairs, go to step 14). If circuit is okay, go to step 13).
10. Locate and repair open in MAF sensor ground circuit. After repairs, go to step 14).
11. Locate and repair open in MAF ignition feed circuit. After repairs, go to step 14).
12. Replace MAF sensor. After replacing sensor, go to step 14).
13. Replace and program replacement PCM. After replacing PCM, go to next step.
14. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for DTC P0102. If scan tool indicates FAILED THIS IGN, repeat step 2). If scan tool does not indicate FAILED THIS IGN, repair is complete.

Check for poor connection at PCM. Check for misrouted MAF sensor wiring harness. Ensure harness is not close to high voltage components. Check for damaged wiring harness. Check for plugged intake air duct or filter element.

DTC P0103 - MAF SENSOR CIRCUIT HIGH FREQUENCY

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Mass Airflow (MAF) sensor measures amount of air entering engine during a given time. PCM uses MAF sensor information for fuel delivery calculations. MAF sensor readings during acceleration are much higher than those during deceleration or idle.

PCM calculates what MAF sensor reading should be received from 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 actual value received from sensor.

Conditions required to set DTC are

1. Engine is running.
2. TP ANGLE is less than 50 percent.
3. System voltage is greater than 8 volts.
4. MAF signal frequency greater than 11,500 Hertz (Hz).
5. Conditions present greater than 0.5 second.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Start engine and allow it to idle. Using scan tool, select ENG 1 data list. Monitor MAF FREQUENCY display. If frequency is less than 11,500 Hz, go to step 4). If frequency is not less than 11,500 Hz, go to next step.
3. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Select SPECIFIC DTC function then enter DTC P0103. If scan tool indicates FAILED THIS IGN, go to next step. If scan tool does not indicate FAILED THIS IGN, see DIAGNOSTIC AIDS.
4. Turn ignition off. Disconnect MAF sensor harness connector. Start engine. Using scan tool, monitor MAF FREQUENCY. If frequency is zero Hz, go to next step. If frequency is not zero Hz, go to step 7).
5. Check for poor connection at MAF sensor connector. Repair as necessary. After repairs, go to step 10). If connector is okay, go to next step.
6. Replace MAF sensor. After replacing sensor, go to step 10).
7. Check for incorrect routing of MAF sensor wiring harness. Ensure harness is not near ignition coils or other high-voltage components. Reroute wiring harness as necessary. After repairs, go to step 10). If wiring harness is routed correctly, go to next step.
8. Check MAF signal circuit terminal connections at PCM. Repair as necessary. After repairs, go to step 10). If terminal connections are okay, go to next step.
9. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
10. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for DTC P0103. If scan tool indicates FAILED THIS IGN, repeat step 2). If scan tool does not indicate FAILED THIS IGN, repair is complete.

Check for faulty connections or damaged harness. Ensure harness is not routed too close to high-voltage wires, such as spark plug cables. If connections and harness appear okay, observe scan tool while moving all related harnesses and connectors. A change in scan tool display indicates fault location.

DTC P0107 - MAP SENSOR CIRCUIT LOW VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Manifold Absolute Pressure (MAP) sensor measures changes in intake manifold pressure (vacuum). A low voltage signal, about 2 volts, is sent to PCM on signal circuit at closed throttle (high vacuum) idle. A high voltage signal, about 4 volts, is sent at wide open throttle (low vacuum).

Conditions required to set DTC are

1. No TP sensor related DTCs present.
2. Engine running.
3. TP angle greater than zero percent with engine speed less than 1000 RPM, or greater than 6 percent with engine speed at greater than 1000 RPM.
4. MAP sensor signal voltage less than 0.1 volt.
5. Listed conditions present for greater than 58 crankshaft revolutions.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Turn ignition on, engine off. Using scan tool, read MAP sensor voltage. If voltage is about zero volts, go to step 5). If voltage is not about zero volts, go to next step.
3. With ignition on, engine off, use scan tool to read and record FAIL RECORDS data. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P0107 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0107 FAILED THIS IGN, see DIAGNOSTIC AIDS.
4. Disconnect MAP sensor harness connector. Connect a jumper wire between MAP sensor harness connector 5-volt reference circuit and signal circuit. If scan tool MAP voltage is about 4.95 volts, go to step 10). If voltage is not about 4.95 volts, go to next step.
5. Turn ignition off. Remove jumper wire. Connect a test light between MAP sensor harness connector signal circuit and battery voltage. Turn ignition on. If voltage is about 4.95 volts, go to next step. If voltage is not 4.95 volts, go to step 8).
6. Turn ignition off. Disconnect PCM connectors. Check PCM harness connector 5-volt reference circuit for open or short to ground. If open or short is found, repair as necessary. After repairs, go to step 12). If no open or short is found, go to next step.
7. Check for faulty connection of 5-volt reference circuit at PCM. If faulty connection is found, repair as necessary. After repairs, go to step 12). If connection is okay, go to step 11).
8. Turn ignition off. Disconnect PCM connectors. Check PCM harness connector MAP signal circuit for open, short to ground or short to sensor ground. If open or short is found, repair as necessary. After repairs, go to step 12). If no open or short is found, go to next step.
9. Check for faulty connection of MAP signal circuit at PCM. If faulty connection is found, repair as necessary. After repairs, go to step 12). If connection is okay, go to step 11).
10. Replace MAP sensor. After replacing sensor, go to step 12).
11. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
12. Turn ignition on, engine off. Using scan tool, read and record FAIL RECORDS DATA, and clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, select SPECIFIC DTC INFO for DTC P0107. If scan tool displays DTC P0107 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P0107 FAILED THIS IGN, repair is complete.

Check for faulty connections or damaged harness. Ensure harness is not routed too close to high-voltage wires, such as spark plug cables. If connections and harness appear okay, observe MAP display on scan tool while moving all related harnesses and connectors. A change in scan tool display indicates fault location.

DTC P0108 - MAP SENSOR CIRCUIT HIGH VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Manifold Absolute Pressure (MAP) sensor measures changes in intake manifold pressure (vacuum). A low voltage signal, 2 volts, is sent to PCM on signal circuit at closed throttle (high vacuum). A high voltage signal, 4 volts, is sent at wide open throttle (low vacuum).

Conditions required to set DTC are

1. No TP sensor related DTCs are set.
2. Engine running.
3. Throttle position less than 30 percent if engine speed is greater than 3000 RPM.
4. Throttle position less than 2 percent if engine speed is less than 3000 RPM.
5. MAP sensor voltage greater than 3.5 volts.
6. Listed conditions present for greater than 58 crankshaft revolutions.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Correct any engine idle or vacuum problems before proceeding. Turn engine on and allow it to idle. Using scan tool, read MAP sensor voltage. If voltage is greater than 3.5 volts, go to step 4). If voltage is not greater than 3.5 volts, go to next step.
3. With ignition on, engine off, use scan tool to read and record FAIL RECORDS data. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P0108 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0108 FAILED THIS IGN, see DIAGNOSTIC AIDS.
4. Turn ignition off. Disconnect MAP sensor harness connector. Turn ignition on. If voltage is zero volts, go to next step. If voltage is not zero volts, go to step 6).
5. Connect a test light between MAP sensor harness connector ground circuit and battery voltage. If test light illuminates, go to step 7). If test light does not illuminate, go to step 9).
6. Check MAP sensor harness connector signal circuit for short to voltage. If short to voltage is found, repair as necessary. After repairs, go to step 16). If short to voltage is not found, go to step 11).
7. Check for faulty connection of ground circuit at MAP sensor. If faulty connection is found, repair as necessary. After repairs, go to step 16). If connection is okay, go to next step.
8. Check for plugged or leaking vacuum supply to MAP sensor. If vacuum supply is okay, go to step 12). If vacuum supply is not okay, go to step 15).
9. Check for faulty MAP sensor ground circuit connection at PCM. If MAP sensor connection is faulty, repair as necessary. After repairs, go to step 16). If connection is okay, go to next step.
10. Check continuity of MAP sensor ground circuit. If resistance is 5 ohms or greater, repair circuit as necessary. After repairs, go to step 16). If resistance is not 5 ohms or greater, go to next step.
11. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to step 16).
12. Turn ignition off. Disconnect PCM connectors. Turn ignition on, engine off. Check PCM harness connector 5-volt reference circuit for short to voltage. If short is found, repair as necessary. After repairs, go to step 16). If no short is found, go to next step.
13. Check for faulty connection at MAP sensor. If faulty connection is found, repair as necessary. After repairs, go to step 16). If connection is okay, go to next step.
14. Replace MAP sensor. After replacing sensor, go to step 16).
15. Repair faulty vacuum source. After repairs, go to next step.
16. Turn ignition on, engine off. Using scan tool, read and record FAIL RECORDS DATA, and clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, select SPECIFIC DTC INFO for DTC P0108. If scan tool displays DTC P0108 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P0108 FAILED THIS IGN, repair is complete.

Check for faulty connections or damaged harness. Ensure harness is not routed too close to high-voltage wires, such as spark plug cables. If connections and harness appear okay, observe MAP display on scan tool while moving all related harness and connectors. A change in scan tool display indicates fault location.

IAT TEMPERATURE-TO-RESISTANCE VALUES

IAT TEMPERATURE-TO-RESISTANCE VALUES

DTC P0112 - IAT SENSOR CIRCUIT LOW VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Intake Air Temperature (IAT) sensor is a thermistor that varies resistance based on temperature. As temperature of sensor increases, resistance decreases. High temperature will result in a low signal voltage. DTC will set when PCM sees an IAT sensor voltage of less than 0.82 volt for 10 seconds after engine runs for 100 seconds.

Conditions required to set DTC are

1. No active ECT, MAF or VSS sensor related DTC.
2. Vehicle driven at 25 MPH or greater.
3. Engine running greater than 30 seconds.
4. IAT greater than 282°F (139°C).
5. Conditions are present for at least 30 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, read INTAKE AIR TEMP. If temperature is greater than 266°F (130°C), go to step 4). If temperature is not as specified, go to next step.
3. Turn ignition on, engine off. Using scan tool, read and record FAIL RECORDS data. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P0112 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0112 FAILED THIS IGN, go to DIAGNOSTIC AIDS.
4. Disconnect IAT sensor harness connector. Using scan tool, read INTAKE AIR TEMP. If sensor temperature is less than -38°F (-39°C), go to step 6). If temperature is -38°F (-39°C) or greater, go to next step.
5. Turn ignition off. Disconnect PCM connectors. Check IAT sensor signal circuit for short to ground. If short is found, go to step 7). If no short is found, go to step 8).
6. Replace IAT sensor. After replacing sensor, go to step 9).
7. Repair IAT sensor signal circuit. After repairs, go to step 9).
8. Replace PCM. Program replacement PCM using required equipment. After replacing and reprogramming PCM, go to next step.
9. Turn ignition on, engine off. Using scan tool, read and record FAIL RECORDS DATA, and clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, select SPECIFIC DTC INFO for DTC P0112. If scan tool displays DTC P0112 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P0112 FAILED THIS IGN, repair is complete.

Check for faulty connections or damaged harness. Ensure harness is not routed too close to high-voltage wires, such as spark plug cables. If connections and harness appear okay, observe IAT display on scan tool while moving all related harness and connectors. A change in scan tool display indicates fault location. Check for skewed IAT sensor. See IAT TEMPERATURE-TO-RESISTANCE VALUES table.

DTC P0113 - IAT SENSOR CIRCUIT HIGH VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Intake Air Temperature (IAT) sensor is a thermistor that varies resistance based on temperature. As temperature of sensor increases, resistance decreases. Low temperature will result in a high signal voltage. DTC will set when PCM sees an IAT sensor voltage of greater than 5 volts.

Conditions required to set DTC are

1. Vehicle speed is less than 35 MPH.
2. No ECT, MAF or VSS sensor DTCs are set.
3. MAF value is less than 12 grams per second.
4. ECT is greater than 140°F (60°C).
5. IAT less than -38°F (-38°C).
6. Conditions present for at least 3 minutes.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Using scan tool, read INTAKE AIR TEMP. If temperature is less than -22°F (-30°C), go to step 4). If temperature is not as specified, go to next step.
3. Turn ignition on, engine off. Using scan tool, read and record FAIL RECORDS data. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P0113 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0113 FAILED THIS IGN, see DIAGNOSTIC AIDS.
4. Disconnect IAT sensor harness connector. Connect a jumper wire between IAT sensor harness connector signal and ground circuits. Using scan tool, read INTAKE AIR TEMP. If temperature is 266°F (130°C), go to step 6). If temperature is not as specified, go to next step.
5. Connect jumper wire between chassis ground and IAT sensor harness connector signal circuit. Using scan tool, read INTAKE AIR TEMP. If temperature is 266°F (130°C), go to step 7). If temperature is not as specified, go to step 8).
6. Check for faulty connection at IAT sensor. If faulty connection is found, repair as necessary. After repairs, go to step 12). If connection is okay, go to step 10).
7. Turn ignition off. Disconnect PCM connectors. Check IAT sensor ground circuit for an open. If open is found, repair as necessary. After repairs are complete, go to step 12). If no open is found, go to step 9).
8. Turn ignition off. Disconnect PCM connectors. Check IAT signal circuit for an open. If open is present, repair circuit as necessary. After repairs are complete, go to step 12). If no open is found, go to next step.
9. Check for faulty IAT signal or ground circuit connection at PCM. If problem is found, repair as necessary. After repairs, go to step 12). If no problem is found, go to step 11).
10. Replace IAT sensor. After replacing sensor, go to step 12).
11. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
12. Turn ignition on, engine off. Using scan tool, read and record FAIL RECORDS DATA, and clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, select SPECIFIC DTC INFO for DTC P0113. If scan tool displays DTC P0113 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P0113 FAILED THIS IGN, repair is complete.

Check for faulty connections or damaged harness. Ensure harness is not routed too close to high-voltage wires, such as spark plug cables. If connections and harness appear okay, observe IAT display on scan tool while moving all related harness and connectors. A change in scan tool display indicates fault location. Check for skewed IAT sensor. See IAT TEMPERATURE-TO-RESISTANCE VALUES table.

ECT TEMPERATURE-TO-RESISTANCE VALUES

ECT TEMPERATURE-TO-RESISTANCE VALUES

DTC P0117 - ECT SENSOR CIRCUIT LOW VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Engine Coolant Temperature (ECT) sensor is a thermistor that varies resistance based on temperature. As temperature of sensor increases, resistance decreases. High temperature will result in a low signal voltage. DTC will set when PCM sees an excessively low ECT sensor voltage signal.

Conditions required to set DTC are

1. ECT greater than 282°F (139°C).
2. Listed conditions present for at least 15 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, read ENG COOL TEMP. If temperature is greater than 266°F (130°C), go to step 4). If temperature is not as specified, go to next step.
3. Turn ignition on, engine off. Using scan tool, read and record FAIL RECORDS data. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P0117 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0117 FAILED THIS IGN, see DIAGNOSTIC AIDS.
4. Disconnect ECT sensor harness connector. Using scan tool, read ENG COOL TEMP. If temperature is -22°F (-30°C) or less, go to step 6). If temperature is not as specified, go to next step.
5. Turn ignition off. Disconnect PCM connectors. Check ECT sensor signal circuit for short to ground. If short is found, repair as necessary. After repairs, go to step 8). If no short is found, go to step 7).
6. Replace ECT sensor. After replacing sensor, go to step 8).
7. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
8. Turn ignition on, engine off. Using scan tool, read and record FAIL RECORDS DATA, and clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, select SPECIFIC DTC INFO for DTC P0117. If scan tool displays DTC P0117 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P0117 FAILED THIS IGN, repair is complete.

Check for faulty connections or damaged harness. Ensure harness is not routed too close to high-voltage wires, such as spark plug cables. If connections and harness appear okay, observe ECT display on scan tool while moving all related harness and connectors. A change in scan tool display indicates fault location.

If DTC P0117 cannot be duplicated, the information included in the FAIL RECORDS data can be useful in determining vehicle mileage since the DTC was last set. If it is determined that the DTC occurs intermittently, performing DTC P1114 diagnosis may isolate cause of fault.

DTC P0118 - ECT SENSOR CIRCUIT HIGH VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Engine Coolant Temperature (ECT) sensor is a thermistor that varies resistance based on temperature. As temperature of sensor increases, resistance decreases. Low temperature will result in a high signal voltage. DTC will set when PCM sees an excessively high ECT sensor voltage signal.

Conditions required to set DTC are

1. ECT sensor signal indicates that coolant temperature reading is less than -36°F (-38°C).
2. Conditions present for longer than 3 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Turn ignition on. Using scan tool, read ENG COOL TEMP. If temperature is less than -22°F (-30°C), go to step 4). If temperature is not as specified, go to next step.
3. Turn ignition on, engine off. Using scan tool, read and record FAIL RECORDS data. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P0118 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0118 FAILED THIS IGN, go to DIAGNOSTIC AIDS.
4. Disconnect ECT sensor harness connector. Connect a jumper wire between ECT sensor harness connector signal and ground circuits. Using scan tool, read ENG COOL TEMP. If temperature is 266°F (130°C), go to step 6). If temperature is not as specified, go to next step.
5. Connect jumper wire between chassis ground and ECT sensor harness connector signal circuit. Using scan tool, read ENG COOL TEMP. If temperature is 266°F (130°C), go to step 7). If temperature is not as specified, go to step 8).
6. Check for faulty connection at ECT sensor. If faulty connection is found, repair as necessary. After repairs, go to step 12). If connection is okay, go to step 10).
7. Turn ignition off. Disconnect PCM connectors. Check ECT sensor ground circuit for an open. If open is found, repair as necessary. After repairs, go to step 12). If no open is found, go to step 9).
8. Turn ignition off. Disconnect PCM connectors. Check ECT signal circuit for an open. If open is found, repair as necessary. After repairs, go to step 12). If no open is found, go to next step.
9. Check for faulty ECT signal or ground circuit connection at PCM. If problem is found, repair as necessary. After repairs, go to step 12). If no problem is found, go to step 11).
10. Replace ECT sensor. After replacing sensor, go to step 12).
11. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
12. Turn ignition on, engine off. Using scan tool, read and record FAIL RECORDS DATA, and clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, select SPECIFIC DTC INFO for DTC P0118. If scan tool displays DTC P0118 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P0118 FAILED THIS IGN, repair is complete.

Check for faulty connections or damaged harness. Ensure harness is not routed too close to high-voltage wires, such as spark plug cables. If connections and harness appear okay, observe ECT display on scan tool while moving all related harness and connectors. A change in scan tool display indicates fault location.

If DTC P0118 cannot be duplicated, the information included in the FAIL RECORDS data can be useful in determining vehicle mileage since the DTC was last set. If it is determined that the DTC occurs intermittently, performing DTC P1114 diagnosis may isolate cause of fault.

DTC P0121 - TP SENSOR PERFORMANCE

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

The Powertrain Control Module (PCM) supplies a 5-volt reference signal and a ground circuit to Throttle Position (TP) sensor, and a signal circuit to monitor changes in throttle angle. TP sensor signal voltage should be about .5 volt at idle and 4.0 volts or greater at wide open throttle.

Conditions for setting DTC are as follows

1. No active TP sensor or MAP sensor DTC.
2. Engine is running.
3. MAP sensor reading is less than 55 kPa.
4. Predicted throttle angle is not close to actual throttle angle.
5. TP sensor angle is greater than 60 percent at 1600 RPM.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Turn ignition on, with engine off. Using scan tool, select ENG 1 data list. Monitor MAP sensor reading. If MAP sensor value is less than 55 kPa, go to next step. If MAP sensor scan tool value is not as specified, go to step 6).
3. Disconnect MAP sensor harness connector. Connect a test light between the 5-volt reference circuit and signal circuit terminals at MAP sensor harness connector. If MAP sensor value is less than 95 kPa, go to step 5). If MAP sensor value is not less than 95 kPa, go to next step.
4. Check for an open or short to ground in MAP sensor signal circuit. Repair as necessary. After repairs, go to step 13). If circuit is okay, go to step 12).
5. Replace MAP sensor. After replacing sensor, go to step 13).
6. Observing scan tool, depress accelerator to floor, then slowly release pedal. TP sensor angle value should increase steadily to 100 percent when pedal is depressed and decrease steadily to zero percent when pedal is released. If TP sensor angle value is as specified, see DIAGNOSTIC AIDS. If TP sensor angle value is not as specified, go to next step.
7. Disconnect TP sensor connector. Observe TP sensor display on scan tool. If TP sensor voltage is near zero volts, go to next step. If TP sensor voltage is not near zero volts, go to step 9).
8. Connect at test light between 5-volt reference circuit and signal circuit terminals at TP sensor harness connector. If scan tool voltage is about 5 volts, go to step 11). If voltage is not about 5 volts, go to step 10).
9. Check TP signal circuit for short to voltage. Check TP sensor ground circuit for high resistance between PCM and TP sensor. Check TP sensor ground circuit for poor connection. Repair as necessary. After repairs, go to step 13). If circuits are okay, go to step 12).
10. Check TP sensor signal circuit or 5-volt reference circuit for high resistance between PCM and TP sensor. Check TP sensor signal circuit or 5-volt reference circuit for a poor connection. Repair as necessary. After repairs, go to step 13). If circuit is okay, go to next step.
11. Replace TP sensor. After replacing sensor, go to step 13).
12. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
13. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for DTC P0121. If scan tool indicates FAILED THIS IGN, repeat step 2). If scan tool does not indicate FAILED THIS IGN, repair is complete.

Check for damages or sticking throttle plate or IAC valve. A throttle valve place or IAC valve that allows too much airflow while throttle should be closed may cause a high idle and DTC P0121 to set.

A skewed MAP signal or faulty MAP sensor or an incorrect MAP signal may cause PCM to incorrectly calculate the predicted TP sensor value during high engine load situations. Check for an unusually low MAP reading. This condition can cause DTC to set.

Check for poor connections at PCM. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connection.

If DTC cannot be duplicated, the information included in the FAIL RECORDS data can be useful in determining vehicle mileage since DTC was last set. If it is determined that DTC is intermittent, performing DTC P1121 or P1122 diagnosis may isolate cause of fault.

DTC P0122 - TP SENSOR CIRCUIT LOW VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Throttle Position (TP) sensor measures amount of throttle opening. PCM uses TP sensor information for fuel delivery calculations. TP sensor readings during acceleration are much higher than those during deceleration or idle.

Conditions for setting DTC

1. Ignition is on.
2. TP sensor voltage less than .16 volt.
3. Conditions present for at least one second.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Turn ignition on, engine off. With throttle closed, use scan tool to read TP sensor voltage. If voltage is less than 0.16 volt, go to step 4). If voltage is not less than 0.16 volt, go to next step.
3. With ignition still on, engine off, use scan tool to read and record FAIL RECORDS data. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P0122 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0122 FAILED THIS IGN, see DIAGNOSTIC AIDS.
4. Disconnect TP sensor harness connector. Connect a jumper wire between TP sensor harness connector 5-volt reference and signal circuits. If voltage is 5 volts, go to step 10). If voltage is not 5 volts, go to next step.
5. Connect a test light between TP sensor harness connector signal circuit and battery voltage. Observe TP sensor display on scan tool. If voltage is 5 volts, go to next step. If voltage is not 5 volts, go to step 8).
6. Turn ignition off. Disconnect PCM connectors. Check PCM harness connector 5-volt reference circuit for open or short to ground. If open or short is found, repair as necessary. After repairs, go to step 13). If circuit is okay, go to next step.
7. Turn ignition off. Check for faulty connection of 5-volt reference circuit at PCM. If faulty connection is found, repair connection as necessary. After repairs, go to step 13). If connection is okay, go to step 12).
8. Turn ignition off. Disconnect PCM connectors. Check PCM harness connector TP signal circuit for open or short to ground. If open or short is found, repair as necessary. After repairs, go to step 13). If circuit is okay, go to next step.
9. Check for faulty connection of TP signal circuit at PCM. If faulty connection is found, repair as necessary. After repairs, go to step 13). If connection is okay, go to step 12).
10. Check for faulty connection of TP signal circuit at TP sensor. If faulty connection is found, repair as necessary. After repairs, go to step 13). If connection is okay, go to next step.
11. Replace TP sensor. After replacing sensor, go to step 13).
12. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
13. Turn ignition on, engine off. Using scan tool, read and record FAIL RECORDS DATA, and clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, select SPECIFIC DTC INFO for DTC P0122. If scan tool displays DTC P0122 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P0122 FAILED THIS IGN, repair is complete.

Check for faulty connections or damaged harness. Ensure harness is not routed too close to high-voltage wires, such as spark plug cables. If connections and harness appear okay, observe TP SENSOR display on scan tool while moving all related harness and connectors. A change in scan tool display indicates fault location.

If DTC cannot be duplicated, the information included in the FAIL RECORDS data can be useful in determining vehicle mileage since DTC was last set. If it is determined that DTC is intermittent, performing DTC P1122 diagnosis may isolate cause of fault.

DTC P0123 - TP SENSOR CIRCUIT HIGH VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Throttle Position (TP) sensor measures amount of throttle opening. PCM uses TP sensor information for fuel delivery calculations. TP sensor readings during acceleration are much higher than those during deceleration or idle.

Conditions required to set DTC are

1. Ignition on.
2. TP sensor signal voltage greater than 4.71 volts.
3. Listed conditions present greater than one second.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing ODB system check, go to next step.
2. Turn ignition on, engine off. Using scan tool, read TP sensor voltage. If voltage is greater than 4.71 volts, go to step 4). If voltage is not greater than 4.71 volts, go to next step.
3. With ignition still on, engine off, using scan tool, read and record FAIL RECORDS data. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P0123 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0123 FAILED THIS IGN, go to DIAGNOSTIC AIDS.
4. Disconnect TP sensor harness connector. If voltage is about zero volt, go to next step. If voltage is not as specified, go to step 6).
5. Connect a test light between TP sensor harness connector ground circuit and battery voltage. If test light illuminates, go to step 7). If test light does not illuminate, go to step 8).
6. Turn ignition off. Disconnect PCM connectors. Turn ignition on. Check TP sensor harness connector signal circuit for short to voltage. If short to voltage is found, repair as necessary. After repairs, go to step 13). If short to voltage is not found, go to step 12).
7. Turn ignition on. While monitoring scan tool TP SENSOR display, disconnect each component (one at a time) that shares common 5-volt reference circuit. If display changes, replace component that causes change. After repairs, go to step 13). If display does not change, go to next step.
8. Turn ignition off. Disconnect PCM connectors. Turn ignition on, engine off. Check PCM harness connector 5-volt reference circuit for short to voltage. If short is found, repair as necessary. After repairs, go to step 13). If no short is found, go to next step.
9. Check for faulty connection at TP sensor. If faulty connection is found, repair as necessary. After repairs, go to step 13). If TP sensor connection is okay, go to step 11).
10. Turn ignition off. Disconnect PCM connectors. Check for faulty TP sensor ground circuit connection at PCM. If faulty connection is found, repair as necessary. After repairs, go to step 13). If PCM connection is okay, go to step 12).
11. Replace TP sensor. After replacing sensor, go to step 13).
12. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
13. Turn ignition on, engine off. Using scan tool, read and record FAIL RECORDS DATA, and clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, select SPECIFIC DTC INFO for DTC P0123. If scan tool displays DTC P0123 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P0123 FAILED THIS IGN, repair is complete.

Check for faulty connections or damaged harness. Ensure harness is not routed too close to high-voltage wires, such as spark plug cables. If connections and harness appear okay, observe TP SENSOR display on scan tool while moving all related harness and connectors. A change in scan tool display indicates fault location.

Turn ignition on, engine off. Using scan tool TP SENSOR display, slowly depress accelerator to wide open throttle. If voltage is greater than 4.71 volts at any time, replace TP sensor.

If DTC cannot be duplicated, the information included in the FAIL RECORDS data can be useful in determining vehicle mileage since DTC was last set. If it is determined that DTC is intermittent, performing DTC P1121 diagnosis may isolate cause of fault.

DTC P0125 - ECT EXCESSIVE TIME TO REACH CLOSED LOOP

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

While engine is warming, PCM reads Engine Coolant Temperature (ECT) sensor to determine how long it takes coolant to reach temperature required for closed loop operation. PCM compares actual time required to a predetermined time.

Conditions required to set DTC are

1. No IAT or ECT sensor DTCs present.
2. IAT is greater than 50°F (10°C).
3. Start-up ECT is 50-62°F (10-30°C).
4. ECT sufficient to allow "closed loop" operation is not achieved within 2 minutes of start-up.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Allow engine to cool completely. Turn engine on and allow it to idle. Using scan tool, monitor ENG COOL TEMP. If temperature increases to 70°F (21°C) within 2 minutes, see DIAGNOSTIC AIDS. If specified temperature is not reached within 2 minutes, go to next step.
3. If any ECT related DTCs are set, diagnose affected DTC before proceeding. If no ECT related DTCs are set, go to next step.
4. Allow engine to cool. Turn ignition on and observe cooling fans. If cooling fans are off, go to next step. If cooling fans are on, diagnose and repair cooling fan problem.
5. Check coolant level. If coolant level is low, go to step 9). If coolant level is okay, go to next step.
6. Check thermostat operation. If thermostat is operating correctly, go to next step. If thermostat is not operating correctly, go to step 9).
7. Compare actual coolant temperature with scan tool ECT value. If temperatures are within 5°F (3°C) of each other, go to step 9). If temperatures are not within 5°F (3°C) of each other, go to next step.
8. Check for high resistance in wiring related to ECT sensor and for poor connections at ECT sensor and PCM. If a problem is found with connections, go to step 10). If no problem is found, go to step 11).
9. Repair cooling system as necessary. After repairs, go to step 12).
10. Repair as necessary. After repairs, go to step 12).
11. Replace ECT sensor. After replacing sensor, go to next step.
12. Allow engine to cool completely. Using scan tool, clear DTCs. Turn engine on and allow it to idle. Using scan tool, monitor ENG COOL TEMP. If temperature increases to greater than 70°F (21°C) within 2 minutes, repair is complete. If specified temperature is not reached within 2 minutes, return to step 2).

Check coolant level. Ensure thermostat and cooling fans are operating properly. Check for high resistance in wiring related to ECT sensor. Check for skewed ECT sensor by comparing actual coolant temperature with scan tool display, and replace ECT sensor if temperatures are not close.

Check for faulty connections or damaged harness. If connections and harness appear okay, observe scan tool while moving all related harness and connectors. A change in scan tool display indicates fault location.

If DTC cannot be duplicated, the information included in the FAIL RECORDS data can be useful in determining vehicle mileage since DTC was last set.

DTC P0131 - HO2S CIRCUIT LOW VOLTAGE SENSOR 1

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Powertrain Control Module (PCM) supplies about .45 volt to Heated Oxygen Sensor 1 (HO2S 1). The HO2S 1 varies voltage from about one volt when exhaust is rich to about .10 volt when exhaust is lean. PCM monitors and stores sensor voltage information and evaluates the voltage samples to determine amount of time sensor voltage is out of range. If PCM detects HO2S 1 voltage is less than predetermined voltage, DTC will set.

Conditions for setting this DTC are as follows

1. No active misfire, fuel injector circuit, TP sensor, EVAP, IAT sensor MAP, sensor, fuel trim, EGR, ECT sensor, MAF sensor or CKP sensor DTCs set.
2. Closed loop air/fuel ratio is 14.4:1-14.9:1.
3. TP sensor angle is 3-40 percent.
4. HO2S 1 signal voltage remains at less than 175 mV during normal closed loop operation.
5. Vehicle is operating in power enrichment mode.
6. HO2S 1 signal voltage remains less than 600 mV.
7. Conditions present for up to 15 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Start engine and operate vehicle within conditions required for setting this DTC. Using scan tool, observe HO2S 1 voltage. If voltage stays at less than 300 mV, go to step 4). If voltage does not stay at less than 300 mV, go to next step.
3. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within the conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for DTC P0131 until DTC P0131 test runs. If scan tool indicates FAILED THIS IGN, go to next step. If scan tool does not indicate FAILED THIS IGN, see DIAGNOSTIC AIDS.
4. Disconnect HO2S 1 connector. Connect a jumper wire between ground and ground circuit terminal at HO2S 1 harness connector. If voltage is about 450 mV, see DIAGNOSTIC AIDS. If voltage is not about 450 mV, go to next step.
5. Turn ignition off. Disconnect PCM harness connector. Check for a short to ground or short to sensor ground circuit in HO2S 1 signal circuit. If circuit is shorted, go to next step. If circuit is okay, go to step 7).
6. Repair wiring as necessary. After repair is completed, go to step 8).
7. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
8. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for DTC P0131 until DTC P0131 test runs. If scan tool indicates FAILED THIS IGN, repeat step 2). If scan tool does not indicate FAILED THIS IGN, repair is complete.

Check oxygen sensor pigtail wire for breaks, contamination or grounding on exhaust manifold. Check for intermittent ground in signal wire between sensor connector and sensor. DO NOT attempt to repair damaged oxygen sensor connector or wiring. If damage is detected, replace oxygen sensor. Check for fuel contamination, improper fuel pressure or exhaust leak, especially near oxygen sensor. Check for vacuum or crankcase leak, causing a lean condition. Check MAF sensor.

DTC P0132 - HO2S CIRCUIT HIGH VOLTAGE SENSOR 1

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Powertrain Control Module (PCM) supplies about .45 volt to Heated Oxygen Sensor 1 (HO2S 1). The HO2S 1 varies voltage from about one volt when exhaust is rich to about .10 volt when exhaust is lean. PCM monitors and stores sensor voltage information and evaluates the voltage samples to determine amount of time sensor voltage is out of range. If PCM detects HO2S 1 voltage is greater than predetermined voltage, DTC will set.

Conditions for setting this DTC are as follows

1. No active misfire, fuel injector circuit, TP sensor, EVAP, IAT sensor, MAP sensor, fuel trim, EGR, ECT sensor, MAF sensor or CKP sensor DTCs set.
2. Closed-loop commanded air/fuel ratio is between 14.4:1-14.9:1.
3. Throttle angle between 3-40 percent.
4. HO2S 1 remains at greater than 975 mV during normal closed loop operation.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Start engine and operate vehicle within conditions required for setting this DTC. Using scan tool, observe HO2S 1 voltage. If voltage stays at greater than 950 mV, go to step 5). If voltage does not stay at greater than 950 mV, go to next step.
3. Operate vehicle in DECEL FUEL MODE (vehicle speed greater than 25 MPH, TP angle less than 3 percent) while monitoring HO2S 1 on scan tool. If voltage stays at greater than 800 mV, go to step 5). If voltage does not stay at greater than 800 mV, go to next step.
4. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for DTC P0132 until DTC P0132 test runs. If scan tool indicates FAILED THIS IGN, go to next step. If scan tool does not indicate FAILED THIS IGN, see DIAGNOSTIC AIDS.
5. Disconnect HO2S 1 connector. Connect a jumper wire between ground and ground circuit terminal at HO2S 1 harness connector. If voltage is about 450 mV, see DIAGNOSTIC AIDS. If voltage is not about 450 mV, go to next step.
6. Turn ignition off. Disconnect PCM connector. Turn ignition on. Using DVOM measure voltage between ground and signal circuit terminal at HO2S 1 harness connector. If voltage is greater than 600 mV, go to next step. If voltage is not greater than 600 mV, go to step 8).
7. Repair short to voltage is HO2S 1 signal circuit. After repairs, go to step 9).
8. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
9. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for DTC P0132 until DTC P0132 test runs. If scan tool indicates FAILED THIS IGN, repeat step 2). If scan tool does not indicate, FAILED THIS IGN, repair is complete.

Check fuel pressure. Perform injector balance test. See SYSTEM/COMPONENT TESTS - 3.1L article. Check for leaking fuel pressure regulator by removing vacuum hose and checking for fuel presence. If fuel is present, replace regulator. Check EVAP canister for fuel saturation. Check MAF sensor. See SYSTEM/COMPONENT TESTS - 3.1L article.

DTC P0133 - HO2S CIRCUIT SLOW RESPONSE SENSOR 1

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

PCM provides about 0.45 volt reference to Heated Oxygen Sensor (HO2S). HO2S sensor signal voltage varies from about one volt when exhaust is rich to about 0.1 volt when exhaust is lean. PCM counts number or times a rich-to-lean and lean-to-rich response is indicated and adds amount of time it takes to complete all transitions. PCM uses this information to determine average time for each transition. If average response time is slow, DTC P0133 will set.

Conditions required to set DTC are

1. No CKP, ECT, EGR pintle position, IAT, MAF, MAP or TP sensor DTCs set.
2. No EVAP system DTC set.
3. No fuel injector circuit, fuel trim or misfire DTCs set.
4. Engine running in closed loop fuel mode for at least one minute.
5. Engine speed 1000-3000 RPM.
6. ECT greater than 185°F (85°C).
7. MAF 15-28 grams per second.
8. Lean-to-rich average transition response time greater than 153 milliseconds.
9. Rich-to-lean average transition response time greater than 148 milliseconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. If any other HO2S DTCs (except P1133 or P1134) are set, diagnose affected DTCs. Start engine and allow it to reach operating temperature. Operate vehicle within conditions required to set DTC. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P0133 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0133 FAILED THIS IGN, see DIAGNOSTIC AIDS.
3. If scan tool also displays DTC P1133 or P1134 FAILED THIS IGN, go to step 8). If scan tool does not display these DTCs, go to next step.
4. Visually inspect exhaust system for leaks near HO2S 1. If leaks are found, repair as necessary. After repairs, return to step 2). If no leaks are found, go to next step.
5. Visually inspect HO2S 1 for secure installation or corrosion on terminals. Check terminal tension at HO2S 1 and PCM. Check for damaged wiring. If a problem is found, go to step 9). If no problem is found, go to next step.
6. Disconnect HO2S 1 connector. Connect jumper wire between HO2S 1 harness connector ground circuit and chassis ground. Using scan tool, read HO2S 1 voltage. If voltage is about 0.45 volt, go to next step. If voltage is not as specified, go to step 10).
7. Connect a jumper wire between HO2S 1 harness connector signal and ground circuits, and chassis ground. If voltage is less than 0.3 volt, go to step 12). If voltage is not less than 0.3 volt, go to step 11).
8. Repair condition causing fuel, sealant, oil or coolant contamination. Replace affected HO2S. After repairs, go to step 13).
9. Repair condition as necessary. After repairs, go to step 13).
10. Repair open HO2S 1 ground circuit or HO2S 1 signal circuit shorted to ground. After repairs, go to step 13).
11. Repair open HO2S 1 signal circuit or faulty PCM connections as necessary. After repairs, go to step 13).
12. Replace HO2S 1. After replacing sensor, go to next step.
13. Using scan tool, read and record FAIL RECORDS DATA, and clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, select SPECIFIC DTC INFO for DTC P0133. If scan tool displays DTC P0133 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P0133 FAILED THIS IGN, repair is complete.

Check for faulty connections or damaged harness. If connections and harness appear okay, observe HO2S 1 display on scan tool while moving all related harness and connectors. A change in scan tool display indicates fault location.

DTC P0134 - HO2S INSUFFICIENT ACTIVITY SENSOR 1

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Powertrain Control Module (PCM) supplies about .45 volt to Heated Oxygen Sensor 1 (HO2S 1). The HO2S 1 generates a voltage that varies from about one volt when exhaust is rich to about .10 volt when exhaust is lean. PCM monitors and stores sensor voltage information and evaluates the voltage samples to determine amount of time sensor voltage is out of range. If PCM detects HO2S 1 voltage remains at or near .45 volt for an extended period of time, DTC will set.

Conditions for setting this DTC are as follows

1. No active misfire, fuel injector circuit, TP sensor, EVAP, IAT sensor, MAP sensor, fuel trim, EGR, ECT sensor, MAF sensor or CKP sensor DTCs set.
2. Engine has been running for greater than 30 seconds.
3. HO2S 1 signal voltage remains 400-500 mV for greater than 10 seconds.
4. Engine coolant temperature is greater than 149°F (65°C).

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Ensure engine is at normal operating temperature. Start engine and increase engine speed to 1200 RPM for 2 minutes. Using scan tool, monitor HO2S 1 voltage. If voltage is varying outside the range of 400-500 mV, go to next step. If voltage is within the 400-500 mV range, go to step 4).
3. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for DTC P0134 until DTC P0134 test runs. If scan tool indicates FAILED THIS IGN, go to next step. If scan tool does not indicate FAILED THIS IGN, see DIAGNOSTIC AIDS.
4. Turn ignition on, with engine off. Disconnect HO2S 1 connector. Connect a jumper wire between ground and sensor signal circuit terminal at HO2S 1 harness connector. If voltage is less than 150 mV, go to step 8). If voltage is not less than 150 mV, go to next step.
5. Turn ignition on, with engine off. Disconnect jumper wire. Using DVOM, measure voltage between heater ground circuit and sensor signal circuit terminals at HO2S 1 harness connector. If voltage is near 450 mV, go to next step. If not, go to step 7).
6. Turn ignition off. Disconnect PCM connector. Check continuity of ground circuit between PCM connector and HO2S 1 harness connector. If resistance is not greater than 5 ohms, go to step 9). If resistance is greater than 5 ohms, repair open in ground circuit. After repair is completed, go to step 13).
7. Turn ignition off. Disconnect PCM connector. Check continuity of signal circuit between PCM and HO2S 1 harness connectors. If resistance is not greater than 5 ohms, go to step 10). If resistance is greater than 5 ohms, repair open in ground circuit. After repair is completed, go to step 13).
8. Turn ignition off. Disconnect and inspect HO2S 1 connector. Inspect for damaged pins, corrosion and loose wires. Repair as necessary. After repairs, go to step 13). If connector is okay, go to step 11).
9. Check for poor HO2S 1 ground circuit terminal connection at PCM connector. Repair terminal as necessary. After repairs, go to step 13). If connector is okay, go to step 12).
10. Check for poor HO2S 1 signal circuit terminal connection at PCM connector. Repair terminal as necessary. After repairs, go to step 13). If connector is okay, go to step 12).
11. Replace oxygen sensor. After replacing sensor, go to step 13).
12. Replace PCM. Program replacement PCM using required equipment. After replacing sensor, go to next step.
13. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for DTC P0134 until DTC P0134 test runs. If scan tool indicates FAILED THIS IGN, repeat step 2). If scan tool does not indicate FAILED THIS IGN, repair is complete.

Check for poor connection at PCM. Check for damaged wiring harness. An intermittent problem can be caused by a poor connection, rubbed-through wire insulation or broken wire inside insulation.

Turn ignition on, with engine off. Using scan tool, monitor HO2S 1 voltage. Voltage should gradually drop to less than 250 mV or rise to greater than 600 mV. If voltage is not as specified, disconnect HO2S 1 connector/ Connector a test light between ignition feed circuit and heater ground circuit terminals at HO2S 1 harness connector. If test light does not illuminate, repair open ignition feed circuit. If test light illuminates, replace HO2S 1.

DTC P0135 - HO2S HEATER CIRCUIT SENSOR 1

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Powertrain Control Module (PCM) runs heater test only after a cold start and only once during an ignition cycle. When engine is started, PCM monitors HO2S 1 voltage. When HO2S 1 voltage indicates a sufficiently active sensor, PCM looks at how much time has elapsed since start-up. If PCM determines that too much time was required for HO2S 1 to become active, DTC will set.

Conditions for setting this DTC are as follows

1. No active misfire, fuel injector circuit, TP sensor, EVAP, IAT sensor, MAP sensor, fuel trim, EGR, ECT sensor, MAF sensor or CKP sensor DTCs set.
2. ECT and IAT is less than 212°F (100°C) at start-up.
3. Average MAF for the sample period is less than 15 gm/s.
4. HO2S 1 signal voltage remains within 150 mV of bias voltage (about 450 mV) for a longer amount of time than it should.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Allow engine to completely cool down before proceeding. Turn ignition on, with engine off. Using scan tool, monitor HO2S 1 voltage. If voltage changes from about 300-600 mV, see DIAGNOSTIC AIDS. If voltage does not change as indicated, go to next step.
3. Remove and inspect fuse for HO2S 1 ignition feed circuit. If fuse is blown, go to step 15). If fuse is okay, go to next step.
4. Turn ignition off. Disconnect HO2S 1 connector. With test light connected to ground, probe ignition feed circuit terminal at HO2S 1 harness connector. If test light does not illuminate, go to step 7). If test light illuminates, go to next step.
5. Connect a test light between heater ground circuit and ignition feed circuit terminals at HO2S 1 harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 8).
6. Allow HO2S 1 to cool for a minimum of 10 minutes. Using DVOM, measure resistance between ignition feed circuit and heater ground circuit terminals at HO2S 1 pigtail. If resistance is 3-10 ohms, go to step 9). If resistance is not 3-10 ohms, go to step 14).
7. Repair open in HO2S 1 ignition feed circuit. After repairs, go to step 16).
8. Repair open in HO2S 1 heater ground circuit. After repairs, go to step 16).
9. Check for poor connection at HO2S 1 harness terminals. Repair as necessary. After repairs, go to step 16). If terminals are okay, go to next step.
10. Turn ignition off. Disconnect PCM connector. Measure resistance of signal circuit and ground circuit between PCM and HO2S 1 harness connector. If both readings are less than 5 ohms, go to next step. If one or both readings are 5 ohms or greater, repair open in appropriate circuit. After repair is completed, go to step 16).
11. Check for poor signal circuit or ground circuit terminal connection at HO2S 1 harness connector. Repair as necessary. After repairs, go to step 16). If terminals are okay, go to next step.
12. Check for poor HO2S 1 ground circuit terminal at PCM. Repair as necessary. After repairs, go to step 16). If terminal is okay, go to next step.
13. Check for poor HO2S 1 signal circuit terminal at PCM. Repair as necessary. After repairs, go to step 16). If terminal is okay, go to next step.
14. Replace oxygen sensor. After replacing sensor, go to step 16).
15. Locate and repair short to ground in HO2S 1 ignition feed circuit. Replace fuse. After repairs, go to next step.
16. Allow engine to completely cool down before proceeding. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Turn ignition on, with engine off. Using scan tool, monitor HO2S 1 voltage. If voltage changes from about 450 mV to 600 mV or from about 450 mV to 300 mV, repair is complete. If voltage does not change as indicated, repeat step 2).

Check for poor connection at PCM. Check for damaged wiring harness. An intermittent problem can be caused by a poor connection, rubbed-through wire insulation or broken wire inside insulation. Reviewing FAIL RECORDS vehicle mileage since diagnostic test last failed may help determine how often condition that caused DTC to be set occurs.

DTC P0137 - HO2S CIRCUIT VOLTAGE LOW SENSOR 2

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Three-Way Catalyst (TWC) system is used to control emissions. PCM uses signal from Heated Oxygen Sensor (HO2S) behind TWC to read efficiency of TWC. PCM will set DTC P0137 if TWC oxygen storage capacity is less than a predetermined threshold.

Conditions required to set DTC are

1. No CKP, ECT, EGR pintle position, IAT, MAF, MAP or TP sensor DTCs set.
2. No EVAP system DTC set.
3. No fuel injector circuit, fuel trim or misfire DTCs set.
4. Closed loop commanded air/fuel ratio is 14.4-14.9:1.
5. TP angle is 3-40 percent.
6. HO2S 2 signal voltage stays less than 0.075 volt during closed loop operation.

Or

1. Vehicle is operating in power enrichment mode.
2. HO2S 2 signal voltage stays less than 0.6 volt.
3. Conditions present for 105 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Start engine and allow it to reach operating temperature. Operate vehicle under conditions required to set DTC. Using scan tool, read HO2S 2 voltage. If voltage stays less than 0.10 volt, go to step 4). If voltage is not specified, go to next step.
3. Turn engine off. Turn ignition on, engine off. Using scan tool, read and record FAIL RECORDS data. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P0137 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0137 FAILED THIS IGN, see DIAGNOSTIC AIDS.
4. Disconnect HO2S 2 harness connector. Connect a jumper wire between HO2S 2 harness connector ground circuit and chassis ground. If voltage is about 0.45 volt, see DIAGNOSTIC AIDS. If voltage is not as specified, go to next step.
5. Turn ignition off. Disconnect PCM connectors. Check HO2S 2 sensor harness connector signal circuit for short to ground. If short is found, go to next step. If no short is found, go to step 7).
6. Repair circuit as necessary. After repairs, go to step 8).
7. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
8. Turn ignition on, engine off. Using scan tool, read and record FAIL RECORDS DATA, and clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, select SPECIFIC DTC INFO for DTC P0137. If scan tool displays DTC P0137 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P0137 FAILED THIS IGN, repair is complete.

Ensure HO2S 2 sensor harness is routed correctly and not contacting exhaust system. Check for faulty PCM grounds. Check fuel system. See BASIC FUEL SYSTEM CHECKS in BASIC TESTING - 3.1L article. Perform injector balance test. See SYSTEM/COMPONENT TESTS - 3.1L article.

Check for vacuum leaks at intake manifold, throttle body, EGR system and crankcase ventilation system. Check for exhaust leaks in front of HO2S 2. Disconnect MAF sensor connector and see if lean condition is corrected. If lean condition is corrected, replace MAF sensor. Check for fuel contamination.

DTC P0138 - HO2S CIRCUIT VOLTAGE HIGH SENSOR 2

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

The Heated Oxygen Sensor 2 (HO2S 2), located at rear of catalytic converter, produces an output signal relative to oxygen storage capacity of catalytic converter. HO2S 2 signal is less active than signal produced by front oxygen sensor.

Conditions for setting this DTC are as follows

1. No active misfire, fuel injector circuit, TP sensor, EVAP, IAT sensor, AMP sensor, fuel trim, EGR, ECT sensor, MAF or CKP sensor DTCs present.
2. Engine coolant temperature is greater than 149°F (65°C).
3. TP sensor angle is 3-40 percent.
4. Air/fuel ratio is 14.4:1-14.9:1.
5. HO2S 2 voltage is greater than 999 mV during normal closed loop operation.
6. HO2S 2 signal voltage remains greater than 200 mV during deceleration fuel mode operation.
7. Condition present for up to 10 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Turn ignition on, with engine off. Using scan tool, observe HO2S 2 voltage. If voltage is greater than 999 mV, go to step 4). If voltage is not greater than 999 mV, go to next step.
3. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for DTC P0138 until DTC P0138 test runs. If scan tool indicates FAILED THIS IGNITION, go to next step. If scan tool does not indicated FAILED THIS IGNITION, see DIAGNOSTIC AIDS.
4. Disconnect HO2S 2 connector. Connect a jumper wire between ground and sensor ground circuit terminal at HO2S 2 harness connector. If voltage is about 450 mV, see DIAGNOSTIC AIDS. If voltage is not about 450 mV, go to next step.
5. Turn ignition off. Disconnect PCM connector. Turn ignition on. Using DVOM, check voltage between ground and HO2S 2 signal circuit terminal at PCM connector. If voltage is greater than 999 mV, go to next step. If voltage is not greater than 999 mV, go to step 7).
6. Repair short to voltage in HO2S 2 signal circuit. After repairs, go to step 8).
7. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
8. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for DTC P0138 until DTC P0138 test runs. If scan tool indicates FAILED THIS IGN, repeat step 2). If scan tool does not indicate FAILED THIS IGN, repair is complete.

Check if fuel pressure is too high. PCM can compensate for some increase; however, if fuel pressure is too high, DTC will set. Check for leaking injector(s) or faulty fuel pressure regulator. See SYSTEM/COMPONENT TESTS - 3.1L article. Check EVAP system for fuel saturation. Check MAF sensor. Check for oxygen sensor silicone contamination. Check TP sensor. See SYSTEM/COMPONENT TESTS - 3.1L article.

DTC P0140 - HO2S CIRCUIT INSUFFICIENT ACTIVITY - SENSOR 2

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Three-Way Catalyst (TWC) system is used to control emissions. PCM uses signal from Heated Oxygen Sensor (HO2S) behind TWC to read efficiency of TWC. PCM will set DTC P0137 if TWC oxygen storage capacity is less than a predetermined threshold.

Conditions required to set DTC are

1. No CKP, ECT, EGR pintle position, IAT, MAF, MAP or TP sensor DTCs set.
2. No EVAP system DTC set.
3. No fuel injector circuit, fuel trim or misfire DTCs set.
4. Engine run time greater than 30 seconds.
5. HO2S signal voltage stays 400-500 mV.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Start engine and allow it to reach operating temperature. Place gear selector in Park or Neutral, and apply parking brake. Increase engine speed to greater than 1200 RPM for 2 minutes. Using scan tool, read HO2S 2 voltage. If voltage is varying outside of 400-500 mV range, go to next step. If voltage is varying as specified, go to step 4).
3. Turn engine off. Turn ignition on, engine off. Using scan tool, read and record FAIL RECORDS data. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P0140 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0140 FAILED THIS IGN, see DIAGNOSTIC AIDS.
4. Disconnect HO2S 2 harness connector. Connect a jumper wire between HO2S 2 harness connector signal and low circuits to ground. If voltage is less than 150 mV, go to step 8). If voltage is not less than 150 mV, go to next step.
5. Remove jumper wire. Using DVOM, check voltage between HO2S 2 harness connector signal and heater ground circuits. If voltage is about 950 mV, go to next step. If voltage is not as specified, go to step 7).
6. Turn ignition off. Disconnect PCM harness connectors. Check resistance of HO2S 2 harness connector ground circuit. If resistance is greater than 5 ohms, repair open or faulty connection. After repairs, go to step 13). If resistance is not greater than 5 ohms, go to step 9).
7. Turn ignition off. Disconnect PCM harness connectors. Check resistance of HO2S 2 harness connector signal circuit. If resistance is greater than 5 ohms, repair open or faulty connection. After repairs, go to step 13). If resistance is not greater than 5 ohms, go to step 10).
8. Check for faulty connection at HO2S 2. If faulty connection is found, repair as necessary. After repairs, go to step 13). If connection is okay, go to step 11).
9. Check for faulty connection at PCM. If faulty connection is found, repair as necessary. After repairs, go to step 13). If connection is okay, go to step 12).
10. Check for faulty connection at PCM. If faulty connection is found, repair as necessary. After repairs, go to step 13). If connection is okay, go to step 12).
11. Replace HO2S 2. After replacing sensor, go to step 13).
12. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
13. Using scan tool, read and record FAIL RECORDS DATA, and clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, select SPECIFIC DTC INFO for DTC P0140. If scan tool displays DTC P0140 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P0140 FAILED THIS IGN, repair is complete.

Check for faulty connections or damaged harness. If connections and harness appear okay, observe HO2S display on scan tool while moving all related harness and connectors. A change in scan tool display indicates fault location. Check HO2S 2 heater operation.

DTC P0141 - HO2S HEATER CIRCUIT SENSOR 2

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

When ignition is turned on, battery voltage is supplied to HO2S heater to provide for faster sensor warm-up, thus allowing sensor to become active in a shorter period of time. PCM reads amount of time necessary for sensor to become active after start-up.

Conditions required to set DTC are

1. No CKP, ECT, EGR pintle position, IAT, MAF, MAP or TP sensor DTCs set.
2. No EVAP system DTC set.
3. No fuel injector circuit, fuel trim or misfire DTCs set.
4. ECT and IAT less than 212°F (100°C) at start-up.
5. Difference between ECT and IAT is within 11°F (6°C) of each other.
6. HO2S 2 voltage remains within 150 mV of bias voltage (about 450 mV) for longer amount of time than it should.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step. NOTE: If engine has been operating, allow engine to cool for about 30 minutes before proceeding with tests.
2. Turn ignition on, engine off. Using scan tool, read HO2S 2 voltage. If voltage is greater than 600 mV or less than 300 mV, see DIAGNOSTIC AIDS. If voltage is not as specified, go to next step.
3. Inspect HO2S 2 ignition feed fuse. If fuse is open, go to step 15). If fuse is okay, go to next step.
4. Turn ignition off. Raise and support vehicle. Disconnect HO2S 2 harness connector. Connect a test light between chassis ground and HO2S 2 ignition feed circuit. If test light illuminates, go to next step. If test light does not illuminate, go to step 7).
5. Connect test light between HO2S 2 harness connector ignition feed and heater ground circuits. If test light illuminates, go to next step. If test light does not illuminate, go to step 8).
6. Allow HO2S 2 to cool for at least 10 minutes. Using DVOM, check resistance between ignition feed and heater ground circuits at HO2S 2. If resistance is 3-10 ohms, go to step 9). If resistance is not as specified, go to step 14).
7. Repair open HO2S 2 ignition feed circuit. After repairs, go to step 16).
8. Repair open HO2S 2 heater ground circuit. After repairs, go to step 16).
9. Check for faulty connection at HO2S 2. If faulty connection is found, repair as necessary and go to step 16). If connection is okay, go to next step.
10. Turn ignition off. Disconnect PCM connectors. Check resistance of HO2S 2 signal and ground circuits. If resistance on either circuit is greater than 5 ohms, repair open or faulty connection as necessary and go to step 16). If resistance is 5 ohms or less, go to next step.
11. Check for faulty connection at HO2S 2 harness connector. If faulty connection is found, repair as necessary. After repairs, go to step 16). If connection is okay, go to next step.
12. Check for faulty ground circuit connection at PCM. If faulty connection is found, repair as necessary. After repairs, go to step 16). If connection is okay, go to next step.
13. Check for faulty HO2S 2 signal circuit connection at PCM. If faulty connection is found, repair as necessary. After repairs, go to step 16). If connection is okay, go to next step.
14. Replace HO2S 2. After replacing sensor, go to step 16).
15. Locate and repair short to ground in HO2S 2 ignition feed circuit, replace fuse. After repairs, go to next step.
16. Allow engine to cool completely. Using scan tool, clear DTCs. Turn ignition on, engine off. Read HO2S 2 voltage. If voltage is greater than 600 mV or less than 300 mV, repair is complete. If voltage is not as specified, return to step 2).

Check for faulty connections or damaged harness. If connections and harness appear okay, observe scan tool while moving all related harness and connectors. A change in scan tool display indicates fault location.

PCM reads HO2S signal voltage and adjusts fuel delivery based on this voltage. A change made to fuel delivery is indicated by Long Term (LT) and Short Term (ST) FUEL TRIM values.

ST FUEL TRIM values change rapidly in response to HO2S signal voltages. These changes fine tune engine fueling. LT FUEL TRIM values change in response to trends in ST fuel trim. LT fuel trim makes coarse adjustments to fueling in order to re-center and restore control to ST fuel trim. LT and ST fuel trim can be read by using a scan tool.

Ideal FUEL TRIM value is about zero. Fuel trim value greater than zero indicates that PCM is adding fuel to compensate for a lean condition. Fuel trim less than zero indicates that PCM is reducing amount of fuel to compensate for rich condition. DTC will set if PCM detects an excessively rich or lean condition.

Conditions for setting DTC

1. No IAC DTCs set at idle.
2. No CKP, ECT, EGR, HO2S, IAT, MAF, MAP or TP sensor DTCs set.
3. No EVAP DTCs set.
4. No misfire or injector circuit DTCs set.
5. ECT 68-230°F (20-110°C).
6. IAT -4 to 149°F (-20 to 65°C).
7. BARO greater than 7 kPa.
8. Engine speed 550-5000 RPM.
9. IAT 0-104°F (-18 to 40°C).
10. MAP 2.6-12.8 psi (0.18-0.90 kg/cm 2 )
11. TP angle less than 90 percent.
12. MAF 3-175 grams per second.
13. Long term fuel trim about maximum authority (+16 percent).
14. Short term fuel trim about maximum authority (+20 percent).
15. Vehicle speed less than 70 MPH.
16. Conditions met in FUEL TRIM CELLS 3, 6, 7 and/or 8.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. If any other DTCs are set, diagnose affected DTCs before proceeding. If no other DTCs are set, go to next step.
3. Operate vehicle in closed loop mode while using scan tool to read LT and ST FUEL TRIM values. If LT FUEL TRIM value is about +16 percent and ST FUEL TRIM value is about +20 percent, go to step 5). If values are not as specified, go to next step.
4. Using scan tool, read and record FAIL RECORDS data. Clear DTCs and operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC while operating vehicle. Continue operating vehicle until DTC P0171 test runs. If scan tool displays DTC P0171 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0171 FAILED THIS IGN, go to DIAGNOSTIC AIDS.
5. Check vacuum hoses for splits, kinks and proper routing. If a problem is found, repair as necessary. After repairs, go to step 22). If no problem is found, go to next step.
6. Check PCV valve for proper installation. If a problem is found, repair as necessary. After repairs, go to step 22). If no problem is found, go to next step.
7. Check throttle body inlet screen for blockage or foreign objects which may partially block airflow sample through MAF sensor. If a problem is found, repair as necessary. After repairs, go to step 22). If no problem is found, go to next step.
8. Start engine. If high or unsteady idle condition exists, go to next step. If Idle is okay, go to step 11).
9. Using scan tool, read IDLE AIR CONTROL (IAC) value. If value is greater than 5 counts, go to step 11). If value is not greater than 5 counts, go to next step.
10. Check throttle body, intake manifold, and EGR valve for vacuum leaks. If a problem is found, repair as necessary. After repairs, go to step 22). If no problem is found, go to next step.
11. Check IAC valve for proper operation. If a problem is found, repair as necessary. After repairs, go to step 22). If no problem is found, go to next step.
12. Check for fuel contamination. If fuel is contaminated, repair condition causing contamination. After repairs, go to step 22). If fuel is okay, go to next step.
13. Check PCM injector, power and sensor grounds for clean and tight connection, and for proper location. If a problem is found, repair as necessary. After repairs, go to step 22). If no problem is found, go to next step.
14. Disconnect MAF sensor harness connector. Operate vehicle in closed loop mode while monitoring scan tool ST FUEL TRIM. If ST FUEL TRIM decreases to about zero percent, go to step 21). If ST FUEL TRIM does not decrease to about zero percent, go to next step.
15. Perform FUEL SYSTEM PRESSURE TEST under BASIC FUEL SYSTEM CHECKS in BASIC TESTING - 3.1L article. If a problem is found, repair as necessary. After repairs, go to step 22). If no problem is found, go to next step.
16. Perform EVAP system check. See FUEL EVAPORATION CONTROL under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM/COMPONENT TESTS - 3.1L article. If a problem is found, repair as necessary. After repairs, go to step 22). If no problem is found, go to next step.
17. Check intake manifold, injector "O" rings, EGR adapter, EGR valve, and EGR feed pipes for vacuum leaks. If a problem is found, repair as necessary. After repairs, go to step 22). If no problem is found, go to next step.
18. Check exhaust system for corrosion, loose or missing hardware. If a problem is found, repair as necessary. After repairs, go to step 22). If no problem is found, go to next step.
19. Perform INJECTOR BALANCE TEST under FUEL SYSTEM in SYSTEM/COMPONENT TESTS - 3.1L article. If a problem is found, repair as necessary and go to step 22). If no problem is found, go to next step.
20. Ensure HO2S is installed securely, and connector and harness are not contacting exhaust manifold or ignition wires. If a problem is found, repair as necessary. After repairs, go to step 22). If no problem is found, go to DIAGNOSTIC AIDS.
21. Replace MAF sensor. After replacing sensor, go to next step.
22. Using scan tool, read and record FAIL RECORDS DATA, and clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, select SPECIFIC DTC INFO for DTC P0171. If scan tool displays DTC P0171 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P0171 FAILED THIS IGN, repair is complete.

Ensure HO2S wiring is routed correctly and not contacting exhaust system. Check for faulty PCM-to-engine ground connections. Check fuel pressure. Check fuel injector operation. Check for vacuum and exhaust leaks. Disconnect MAF sensor connector and see if lean condition is corrected. If lean condition is corrected, replace MAF sensor.

Check for fuel contamination. Check for faulty connections or damaged harness. If connections and harness appear okay, observe scan tool HO2S 1 display while moving all related harness and connectors. A change in scan tool display indicates fault location.

PCM monitors oxygen sensor signal voltage and adjusts fuel delivery based on signal voltage. A change made to fuel delivery is indicated by the long and short term fuel trim values. Ideal fuel trim value is about 128 (zero percent).

If HO2S signals are indicating a lean condition, the PCM will add fuel, resulting in fuel trim values greater than zero percent. If a rich condition is detected, fuel trim values will be less than zero percent, indicating that PCM is reducing amount of fuel delivered.

Conditions for setting this DTC are as follows

1. No active misfire, fuel injector circuit, TP sensor, EVAP, IAT sensor, MAP sensor, fuel trim, EGR, ECT sensor, MAF sensor or CKP sensor DTCs set.
2. ECT is 68-230°F (20-110°C).
3. IAT 0-149°F (-18 to 65°C).
4. TP sensor angle is less than 90 percent.
5. Vehicle speed is less than 75 MPH.
6. Engine speed is 550-5000 RPM.
7. Long Term (LT) fuel trim is about +16 percent.
8. Short Term (ST) fuel trim is about +20 percent.
9. BARO is greater than 70 kPa.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. If any other DTCs are set, diagnose DTCs as necessary before proceeding. If no other DTCs are set, go to next step.
3. Start and warm engine to normal operating temperature. Ensure system is in closed loop. Using scan tool, select ENG 1 data list. Observe L.T. FUEL TRIM and S.T. FUEL TRIM. If L.T. FUEL TRIM is about -16 percent and S.T. FUEL TRIM is about -11 percent, go to step 5). If fuel trim is not as specified, go to next step.
4. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for DTC P0171 until DTC P0171 test runs. If scan tool indicates FAILED THIS IGN, go to next step. If scan tool does not indicate FAILED THIS IGN, see DIAGNOSTIC AIDS.
5. Inspect air filter element. Replace as necessary. After replacing air filter element, go to step 21). If air filter element is okay, go to next step.
6. Check for collapsed or restricted air intake duct. Repair as necessary. After repairs, go to step 21). If air duct is okay, go to next step.
7. Inspect throttle body inlet screen for damage or blockage. Repair as necessary. After repairs, go to step 21). If inlet screen is okay, go to next step.
8. Start engine and check idle quality. If idle is high or rough, go to next step. If idle is okay, go to step 11).
9. Allow engine to idle. Using scan tool, observe IDLE AIR CONTROL display. If counts are greater than 100, go to step 11). If counts are not greater than 100, go to next step.
10. Turn ignition off. Inspect throttle body bore, throttle plate and IAC passages for coking and foreign objects. Repair as necessary. After repairs, go to step 22). If no problem is found, go to next step.
11. Check Idle Air Control (IAC) valve operation. See SYSTEM/COMPONENT TESTS - 3.1L article. Repair as necessary. After repairs, go to step 21). If IAC valve is functioning properly, go to step 13).
12. Disconnect vacuum hose from fuel pressure regulator and check hose for presence of fuel. If fuel is present, replace fuel pressure regulator. After replacing pressure regulator, go to step 21). If fuel pressure regulator is okay, go to next step.
13. Turn ignition on. Monitor TP angle display on scan tool while slowly depressing accelerator pedal. If TP angle display increase steadily from 0-100 percent (wide-open throttle), go to next step. If TP angle display does not increase as specified, go to step 19).
14. Disconnect MAF sensor connector. Start engine and allow it to idle. Ensure system is in closed loop. Using scan tool, observe ST FUEL TRIM and LT FUEL TRIM display. If both values change to about zero percent, go to step 21). If one or both values do not change to about zero percent, go to next step.
15. Perform BASIC FUEL SYSTEM CHECKS in BASIC TESTING - 3.1L article. Repair fuel system as necessary. After repairs, go to step 22). If fuel system is okay, go to next step.
16. Check fuel evaporation system for proper operation. Ensure canister purge solenoid is functioning properly. See SYSTEM/COMPONENT TESTS - 3.1L article. Repair as necessary. After repairs, go to step 21). If fuel evaporation system is functioning properly, go to next step.
17. Perform INJECTOR BALANCE TEST. See FUEL SYSTEM in SYSTEM/COMPONENT TESTS - 3.1L article. Repair as necessary. After repairs, go to step 21). If no problems were found, go to next step.
18. Visually and physically inspect HO2S 1 for silicon contamination (White powdery deposits). If contamination is evident, replace sensor. After replacing sensor, go to step 21). If sensor is okay, see DIAGNOSTIC AIDS.
19. Check TP sensor mounting screws. Tighten or replace screws as necessary. If screws are okay, replace TP sensor. After replacing sensor, go to step 21).
20. Replace MAF sensor. After replacing sensor, go to next step.
21. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info until DTC P0171 test runs. If scan tool indicates FAILED THIS IGN, repeat step 2). If scan tool does not indicate FAILED THIS IGN, repair is complete.

Check for poor connection at PCM. Check for damaged wiring harness. An intermittent problem can be caused by a poor connection, rubbed-through wire insulation or broken wire inside insulation. Reviewing FAIL RECORDS vehicle mileage since diagnostic test last failed may help determine how often condition that caused DTC to be set occurs.

DTC P0201 - INJECTOR NO. 1 CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

PCM controls fuel injector control circuit using an ignition feed driver and ground circuit within the PCM. The driver has the ability to detect an electrical malfunction in ignition feed or ground circuit. If an electrical malfunction occurs in fuel injector circuit for affected cylinder, ignition feed driver signals PCM to set DTC.

Conditions for setting DTC

1. Engine running.
2. Incorrect voltage level being detected on an injector driver circuit.
3. Conditions present for at least 30 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Start and operate engine at idle. Using scan tool, monitor SPECIFIC DTC. If scan tool indicates that this DTC failed this ignition cycle, go to step 4). If scan does not indicate that this DTC failed this ignition cycle, go to next step.
3. Turn ignition on, engine off. Using scan tool, review and record FAIL RECORDS data. Operate vehicle in fail conditions parameter. If scan tool indicates that this DTC failed this ignition cycle, go to next step. If scan tool does not indicate that this DTC failed this ignition cycle, see DIAGNOSTIC AIDS.
4. Using scan tool, enter OUTPUT DRIVER DATA menu. If scan tool indicates that cylinder No. 1 injector circuit is STUCK HIGH, go to step 6). If scan tool does not indicate that cylinder No. 1 injector circuit is STUCK HIGH, go to next step.
5. If scan tool indicates that cylinder No. 1 injector circuit is STUCK LOW, go to step 10). If scan tool does not indicate that cylinder No. 1 injector circuit is STUCK LOW, see DIAGNOSTIC AIDS.
6. Turn ignition off. Disconnect 10-pin fuel injector connector. Crank engine. While cranking engine, if scan tool indicates that cylinder No. 1 injector circuit is STUCK LOW, go to next step. If scan tool does not indicate that cylinder No. 1 injector circuit is STUCK LOW, go to step 9).
7. Turn ignition off. Disconnect PCM harness connector. Turn ignition on, engine off. Check voltage between cylinder No. 1 fuel injector control circuit and ground. If voltage reading is battery voltage, go to next step. If voltage reading is not battery voltage, go to step 15).
8. Locate and repair short to voltage in cylinder No. 1 fuel injector control circuit. After repairs, go to step 16).
9. If scan tool indicates that No. 1 injector control circuit is STUCK LOW, check affected fuel injector. See SYSTEM/COMPONENT TESTS - 3.1L article.
10. Disconnect 10-pin fuel injector harness connector. Using a test light connected to battery voltage, probe injector No. 1 control circuit at PCM side of 10-pin connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 12).
11. Disconnect PCM harness connector. Using a test light connected to battery voltage, probe injector No. 1 control circuit at PCM connector. If test light illuminates, go to step 14). If test light does not illuminate, go to step 15).
12. With test light still connected, crank engine. If test light flashes, check affected fuel injector. See SYSTEM/COMPONENT TESTS - 3.1L article. If test light does not flash, go to next step.
13. Check cylinder No. 1 injector driver circuit between 10-pin injector connector and PCM for an open circuit. Repair as necessary. After repairs, go to step 16).
14. Locate and repair short to ground in fuel injector driver circuit between PCM and 10-pin injector connector. After repairs, go to next step.
15. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
16. Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle with the FAIL RECORDS conditions. Check for DTCs. If this DTC is set, go to step 2). If this DTC is not set, system is okay.

Monitor injector fault parameter on scan tool. Wiggle electrical harnesses for affected electrical circuit. If status changes on tool, an intermittent problem is present. Check for poor connections at PCM. Check for damaged harness.

DTC P0202 - INJECTOR NO. 2 CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

PCM controls fuel injector control circuit using an ignition feed driver and ground circuit within the PCM. The driver has the ability to detect an electrical malfunction in ignition feed or ground circuit. If an electrical malfunction occurs in fuel injector circuit for affected cylinder, ignition feed driver signals PCM to set DTC.

Conditions for setting DTC

1. Engine running.
2. Incorrect voltage level being detected on an injector driver circuit.
3. Conditions present for at least 30 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Start and operate engine at idle. Using scan tool, monitor SPECIFIC DTC. If scan tool indicates that this DTC failed this ignition cycle, go to step 4). If scan does not indicate that this DTC failed this ignition cycle, go to next step.
3. Turn ignition on, engine off. Using scan tool, review and record FAIL RECORDS data. Operate vehicle in fail conditions parameter. If scan tool indicates that this DTC failed this ignition cycle, go to next step. If scan tool does not indicate that this DTC failed this ignition cycle, see DIAGNOSTIC AIDS.
4. Using scan tool, enter OUTPUT DRIVER DATA menu. If scan tool indicates that cylinder No. 2 injector circuit is STUCK HIGH, go to step 6). If scan tool does not indicate that cylinder No. 2 injector circuit is STUCK HIGH, go to next step.
5. If scan tool indicates that cylinder No. 2 injector circuit is STUCK LOW, go to step 10). If scan tool does not indicate that cylinder No. 2 injector circuit is STUCK LOW, see DIAGNOSTIC AIDS.
6. Turn ignition off. Disconnect 10-pin fuel injector connector. Crank engine. While cranking engine, if scan tool indicates that cylinder No. 2 injector circuit is STUCK LOW, go to next step. If scan tool does not indicate that cylinder No. 2 injector circuit is STUCK LOW, go to step 9).
7. Turn ignition off. Disconnect PCM harness connector. Turn ignition on, engine off. Check voltage between cylinder No. 2 fuel injector control circuit and ground. If voltage reading is battery voltage, go to next step. If voltage reading is not battery voltage, go to step 15).
8. Locate and repair short to voltage in cylinder No. 2 fuel injector control circuit. After repairs, go to step 16).
9. If scan tool indicates that No. 2 injector control circuit is STUCK LOW, check affected fuel injector. See SYSTEM/COMPONENT TESTS - 3.1L article.
10. Disconnect 10-pin fuel injector harness connector. Using a test light connected to battery voltage, probe injector No. 2 control circuit at PCM side of 10-pin connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 12).
11. Disconnect PCM harness connector. Using a test light connected to battery voltage, probe injector No. 2 control circuit at PCM connector. If test light illuminates, go to step 14). If test light does not illuminate, go to step 15).
12. With test light still connected, crank engine. If test light flashes, check affected fuel injector. See SYSTEM/COMPONENT TESTS - 3.1L article. If test light does not flash, go to next step.
13. Check cylinder No. 2 injector driver circuit between 10-pin injector connector and PCM for an open circuit. Repair as necessary. After repairs, go to step 16).
14. Locate and repair short to ground in fuel injector driver circuit between PCM and 10-pin injector connector. After repairs, go to next step.
15. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
16. Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle with the FAIL RECORDS conditions. Check for DTCs. If this DTC is set, go to step 2). If this DTC is not set, system is okay.

Monitor injector fault parameter on scan tool. Wiggle electrical harnesses for affected electrical circuit. If status changes on tool, an intermittent problem is present. Check for poor connections at PCM. Check for damaged harness.

DTC P0203 - INJECTOR NO. 3 CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

PCM controls fuel injector control circuit using an ignition feed driver and ground circuit within the PCM. The driver has the ability to detect an electrical malfunction in ignition feed or ground circuit. If an electrical malfunction occurs in fuel injector circuit for affected cylinder, ignition feed driver signals PCM to set DTC.

Conditions for setting DTC

1. Engine running.
2. Incorrect voltage level being detected on an injector driver circuit.
3. Conditions present for at least 30 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Start and operate engine at idle. Using scan tool, monitor SPECIFIC DTC. If scan tool indicates that this DTC failed this ignition cycle, go to step 4). If scan does not indicate that this DTC failed this ignition cycle, go to next step.
3. Turn ignition on, engine off. Using scan tool, review and record FAIL RECORDS data. Operate vehicle in fail conditions parameter. If scan tool indicates that this DTC failed this ignition cycle, go to next step. If scan tool does not indicate that this DTC failed this ignition cycle, see DIAGNOSTIC AIDS.
4. Using scan tool, enter OUTPUT DRIVER DATA menu. If scan tool indicates that cylinder No. 3 injector circuit is STUCK HIGH, go to step 6). If scan tool does not indicate that cylinder No. 3 injector circuit is STUCK HIGH, go to next step.
5. If scan tool indicates that cylinder No. 3 injector circuit is STUCK LOW, go to step 10). If scan tool does not indicate that cylinder No. 3 injector circuit is STUCK LOW, see DIAGNOSTIC AIDS.
6. Turn ignition off. Disconnect 10-pin fuel injector connector. Crank engine. While cranking engine, if scan tool indicates that cylinder No. 3 injector circuit is STUCK LOW, go to next step. If scan tool does not indicate that cylinder No. 3 injector circuit is STUCK LOW, go to step 9).
7. Turn ignition off. Disconnect PCM harness connector. Turn ignition on, engine off. Check voltage between cylinder No. 3 fuel injector control circuit and ground. If voltage reading is battery voltage, go to next step. If voltage reading is not battery voltage, go to step 15).
8. Locate and repair short to voltage in cylinder No. 3 fuel injector control circuit. After repairs, go to step 16).
9. If scan tool indicates that No. 3 injector control circuit is STUCK LOW, check affected fuel injector. See SYSTEM/COMPONENT TESTS - 3.1L article.
10. Disconnect 10-pin fuel injector harness connector. Using a test light connected to battery voltage, probe injector No. 3 control circuit at PCM side of 10-pin connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 12).
11. Disconnect PCM harness connector. Using a test light connected to battery voltage, probe injector No. 3 control circuit at PCM connector. If test light illuminates, go to step 14). If test light does not illuminate, go to step 15).
12. With test light still connected, crank engine. If test light flashes, check affected fuel injector. See SYSTEM/COMPONENT TESTS - 3.1L article. If test light does not flash, go to next step.
13. Check cylinder No. 3 injector driver circuit between 10-pin injector connector and PCM for an open circuit. Repair as necessary. After repairs, go to step 16).
14. Locate and repair short to ground in fuel injector driver circuit between PCM and 10-pin injector connector. After repairs, go to next step.
15. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
16. Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle with the FAIL RECORDS conditions. Check for DTCs. If this DTC is set, go to step 2). If this DTC is not set, system is okay.

Monitor injector fault parameter on scan tool. Wiggle electrical harnesses for affected electrical circuit. If status changes on tool, an intermittent problem is present. Check for poor connections at PCM. Check for damaged harness.

DTC P0204 - INJECTOR NO. 4 CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

PCM controls fuel injector control circuit using an ignition feed driver and ground circuit within the PCM. The driver has the ability to detect an electrical malfunction in ignition feed or ground circuit. If an electrical malfunction occurs in fuel injector circuit for affected cylinder, ignition feed driver signals PCM to set DTC.

Conditions for setting DTC

1. Engine running.
2. Incorrect voltage level being detected on an injector driver circuit.
3. Conditions present for at least 30 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Start and operate engine at idle. Using scan tool, monitor SPECIFIC DTC. If scan tool indicates that this DTC failed this ignition cycle, go to step 4). If scan does not indicate that this DTC failed this ignition cycle, go to next step.
3. Turn ignition on, engine off. Using scan tool, review and record FAIL RECORDS data. Operate vehicle in fail conditions parameter. If scan tool indicates that this DTC failed this ignition cycle, go to next step. If scan tool does not indicate that this DTC failed this ignition cycle, see DIAGNOSTIC AIDS.
4. Using scan tool, enter OUTPUT DRIVER DATA menu. If scan tool indicates that cylinder No. 4 injector circuit is STUCK HIGH, go to step 6). If scan tool does not indicate that cylinder No. 4 injector circuit is STUCK HIGH, go to next step.
5. If scan tool indicates that cylinder No. 4 injector circuit is STUCK LOW, go to step 10). If scan tool does not indicate that cylinder No. 4 injector circuit is STUCK LOW, see DIAGNOSTIC AIDS.
6. Turn ignition off. Disconnect 10-pin fuel injector connector. Crank engine. While cranking engine, if scan tool indicates that cylinder No. 4 injector circuit is STUCK LOW, go to next step. If scan tool does not indicate that cylinder No. 4 injector circuit is STUCK LOW, go to step 9).
7. Turn ignition off. Disconnect PCM harness connector. Turn ignition on, engine off. Check voltage between cylinder No. 4 fuel injector control circuit and ground. If voltage reading is battery voltage, go to next step. If voltage reading is not battery voltage, go to step 15).
8. Locate and repair short to voltage in cylinder No. 4 fuel injector control circuit. After repairs, go to step 16).
9. If scan tool indicates that No. 4 injector control circuit is STUCK LOW, check affected fuel injector. See SYSTEM/COMPONENT TESTS - 3.1L article.
10. Disconnect 10-pin fuel injector harness connector. Using a test light connected to battery voltage, probe injector No. 4 control circuit at PCM side of 10-pin connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 12).
11. Disconnect PCM harness connector. Using a test light connected to battery voltage, probe injector No. 4 control circuit at PCM connector. If test light illuminates, go to step 14). If test light does not illuminate, go to step 15).
12. With test light still connected, crank engine. If test light flashes, check affected fuel injector. See SYSTEM/COMPONENT TESTS - 3.1L article. If test light does not flash, go to next step.
13. Check cylinder No. 4 injector driver circuit between 10-pin injector connector and PCM for an open circuit. Repair as necessary. After repairs, go to step 16).
14. Locate and repair short to ground in fuel injector driver circuit between PCM and 10-pin injector connector. After repairs, go to next step.
15. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
16. Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle with the FAIL RECORDS conditions. Check for DTCs. If this DTC is set, go to step 2). If this DTC is not set, system is okay.

Monitor injector fault parameter on scan tool. Wiggle electrical harnesses for affected electrical circuit. If status changes on tool, an intermittent problem is present. Check for poor connections at PCM. Check for damaged harness.

DTC P0205 - INJECTOR NO. 5 CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

PCM controls fuel injector control circuit using an ignition feed driver and ground circuit within the PCM. The driver has the ability to detect an electrical malfunction in ignition feed or ground circuit. If an electrical malfunction occurs in fuel injector circuit for affected cylinder, ignition feed driver signals PCM to set DTC.

Conditions for setting DTC

1. Engine running.
2. Incorrect voltage level being detected on an injector driver circuit.
3. Conditions present for at least 30 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Start and operate engine at idle. Using scan tool, monitor SPECIFIC DTC. If scan tool indicates that this DTC failed this ignition cycle, go to step 4). If scan does not indicate that this DTC failed this ignition cycle, go to next step.
3. Turn ignition on, engine off. Using scan tool, review and record FAIL RECORDS data. Operate vehicle in fail conditions parameter. If scan tool indicates that this DTC failed this ignition cycle, go to next step. If scan tool does not indicate that this DTC failed this ignition cycle, see DIAGNOSTIC AIDS.
4. Using scan tool, enter OUTPUT DRIVER DATA menu. If scan tool indicates that cylinder No. 5 injector circuit is STUCK HIGH, go to step 6). If scan tool does not indicate that cylinder No. 5 injector circuit is STUCK HIGH, go to next step.
5. If scan tool indicates that cylinder No. 5 injector circuit is STUCK LOW, go to step 10). If scan tool does not indicate that cylinder No. 5 injector circuit is STUCK LOW, see DIAGNOSTIC AIDS.
6. Turn ignition off. Disconnect 10-pin fuel injector connector. Crank engine. While cranking engine, if scan tool indicates that cylinder No. 5 injector circuit is STUCK LOW, go to next step. If scan tool does not indicate that cylinder No. 5 injector circuit is STUCK LOW, go to step 9).
7. Turn ignition off. Disconnect PCM harness connector. Turn ignition on, engine off. Check voltage between cylinder No. 5 fuel injector control circuit and ground. If voltage reading is battery voltage, go to next step. If voltage reading is not battery voltage, go to step 15).
8. Locate and repair short to voltage in cylinder No. 5 fuel injector control circuit. After repairs, go to step 16).
9. If scan tool indicates that No. 5 injector control circuit is STUCK LOW, check affected fuel injector. See SYSTEM/COMPONENT TESTS - 3.1L article.
10. Disconnect 10-pin fuel injector harness connector. Using a test light connected to battery voltage, probe injector No. 5 control circuit at PCM side of 10-pin connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 12).
11. Disconnect PCM harness connector. Using a test light connected to battery voltage, probe injector No. 5 control circuit at PCM connector. If test light illuminates, go to step 14). If test light does not illuminate, go to step 15).
12. With test light still connected, crank engine. If test light flashes, check affected fuel injector. See SYSTEM/COMPONENT TESTS - 3.1L article. If test light does not flash, go to next step.
13. Check cylinder No. 5 injector driver circuit between 10-pin injector connector and PCM for an open circuit. Repair as necessary. After repairs, go to step 16).
14. Locate and repair short to ground in fuel injector driver circuit between PCM and 10-pin injector connector. After repairs, go to next step.
15. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
16. Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle with the FAIL RECORDS conditions. Check for DTCs. If this DTC is set, go to step 2). If this DTC is not set, system is okay.

Monitor injector fault parameter on scan tool. Wiggle electrical harnesses for affected electrical circuit. If status changes on tool, an intermittent problem is present. Check for poor connections at PCM. Check for damaged harness.

DTC P0206 - INJECTOR NO. 6 CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

PCM controls fuel injector control circuit using an ignition feed driver and ground circuit within the PCM. The driver has the ability to detect an electrical malfunction in ignition feed or ground circuit. If an electrical malfunction occurs in fuel injector circuit for affected cylinder, ignition feed driver signals PCM to set DTC.

Conditions for setting DTC

1. Engine running.
2. Incorrect voltage level being detected on an injector driver circuit.
3. Conditions present for at least 30 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Start and operate engine at idle. Using scan tool, monitor SPECIFIC DTC. If scan tool indicates that this DTC failed this ignition cycle, go to step 4). If scan does not indicate that this DTC failed this ignition cycle, go to next step.
3. Turn ignition on, engine off. Using scan tool, review and record FAIL RECORDS data. Operate vehicle in fail conditions parameter. If scan tool indicates that this DTC failed this ignition cycle, go to next step. If scan tool does not indicate that this DTC failed this ignition cycle, see DIAGNOSTIC AIDS.
4. Using scan tool, enter OUTPUT DRIVER DATA menu. If scan tool indicates that cylinder No. 6 injector circuit is STUCK HIGH, go to step 6). If scan tool does not indicate that cylinder No. 6 injector circuit is STUCK HIGH, go to next step.
5. If scan tool indicates that cylinder No. 6 injector circuit is STUCK LOW, go to step 10). If scan tool does not indicate that cylinder No. 6 injector circuit is STUCK LOW, see DIAGNOSTIC AIDS.
6. Turn ignition off. Disconnect 10-pin fuel injector connector. Crank engine. While cranking engine, if scan tool indicates that cylinder No. 6 injector circuit is STUCK LOW, go to next step. If scan tool does not indicate that cylinder No. 6 injector circuit is STUCK LOW, go to step 9).
7. Turn ignition off. Disconnect PCM harness connector. Turn ignition on, engine off. Check voltage between cylinder No. 6 fuel injector control circuit and ground. If voltage reading is battery voltage, go to next step. If voltage reading is not battery voltage, go to step 15).
8. Locate and repair short to voltage in cylinder No. 6 fuel injector control circuit. After repairs, go to step 16).
9. If scan tool indicates that No. 6 injector control circuit is STUCK LOW, check affected fuel injector. See SYSTEM/COMPONENT TESTS - 3.1L article.
10. Disconnect 10-pin fuel injector harness connector. Using a test light connected to battery voltage, probe injector No. 6 control circuit at PCM side of 10-pin connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 12).
11. Disconnect PCM harness connector. Using a test light connected to battery voltage, probe injector No. 6 control circuit at PCM connector. If test light illuminates, go to step 14). If test light does not illuminate, go to step 15).
12. With test light still connected, crank engine. If test light flashes, check affected fuel injector. See SYSTEM/COMPONENT TESTS - 3.1L article. If test light does not flash, go to next step.
13. Check cylinder No. 6 injector driver circuit between 10-pin injector connector and PCM for an open circuit. Repair as necessary. After repairs, go to step 16).
14. Locate and repair short to ground in fuel injector driver circuit between PCM and 10-pin injector connector. After repairs, go to next step.
15. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
16. Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle with the FAIL RECORDS conditions. Check for DTCs. If this DTC is set, go to repeat step 2). If this DTC is not set, system is okay.

Monitor injector fault parameter on scan tool. Wiggle electrical harnesses for affected electrical circuit. If status changes on tool, an intermittent problem is present. Check for poor connections at PCM. Check for damaged harness.

DTC P0230 - FUEL PUMP CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Fuel pump is powered by fuel pump relay. PCM energizes fuel pump relay at ignition on for 2-3 seconds. Fuel pump will remain on for as long as PCM receives reference pulse from electronic ignition system.

Conditions for setting DTC

1. Ignition is on.
2. PCM detects an electrical malfunction on fuel pump relay control circuit.
3. Conditions met for .5 second.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Connect a test light between fuel pump relay connector cavities for fuel pump relay control circuit and relay ground. Install scan tool. Turn ignition on, with engine off. Using scan tool, command fuel pump relay on and off. If test light illuminates when fuel pump is commanded on, go to step 7). If test light does not illuminate when fuel pump is commanded on, go to next step.
3. Turn ignition off. Disconnect PCM harness connector. Using test light connected to battery voltage, probe fuel pump relay control circuit at PCM connector. If test light illuminates, go to step 9). If test light does not illuminate, go to next step.
4. Using test light connected to battery voltage, probe fuel pump relay ground circuit. If test light illuminates, go to next step. If test light does not illuminate, go to step 10).
5. Check for open in fuel pump relay control circuit between PCM and fuel pump relay. Repair as necessary. After repairs, go to step 14). If circuit is okay, go to next step.
6. Check fuel pump relay control circuit for poor terminal connection at PCM. Repair as necessary. After repairs, go to step 14). If circuit is okay, go to step 12).
7. Turn ignition off. Disconnect PCM harness connector. Turn ignition on, with engine off. Using test light connected to ground, probe fuel pump relay control circuit at PCM connector. If test light illuminates, go to step 13). If test light does not illuminate, go to next step.
8. Check for poor terminal connection at fuel pump relay connector. Repair as necessary. After repairs, go to step 14). If connections are okay, go to step 11).
9. Locate and repair short to ground in fuel pump relay ground circuit. After repairs, go to step 14).
10. Locate and repair open in fuel pump relay ground circuit. After repairs, go to step 14).
11. Replace fuel pump relay. After replacing relay, go to step 14).
12. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to step 14).
13. Locate and repair short to voltage in fuel pump control circuit. After repairs, go to next step.
14. Using scan tool, select DTC, CLEAR INFO function. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter this DTC. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2).

Scan tool will appear not to run if diagnostic passes. Using FREEZE FRAME and/or FAILURE RECORDS may aid in locating an intermittent condition. An intermittent may be caused by a poor connection, rubbed-through wire insulation or a wire broken inside of insulation. Check for poor connections at PCM or fuel pump relay.

Misfire is detected using Camshaft Position (CMP) and Crankshaft Position (CKP) sensors. When PCM senses CKP deceleration not associated with normal engine speed reduction, CMP is used to determine misfiring cylinder. PCM determines misfires on each cylinder and evaluates a random misfire and set DTC.

Conditions for setting DTC

1. No VSS DTCs set.
2. No CKP, CMP, ECT, MAF, MAP or TP sensor DTCs set.
3. Engine speed 450-5800 RPM.
4. System voltage 9-16 volts.
5. ECT 21-248°F (-6 to 120°C).
6. Throttle angle steady.
7. PCM detects crankshaft RPM variation, indicating a misfire which could cause catalytic convertor damage or high emissions.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. If DTC P1200 is also set, go to DTC P1200. If DTC P1200 is not set, go to next step.
3. Start engine and allow it to idle. Using scan tool, read and record FREEZE FRAME data. Operate vehicle within conditions noted in FREEZE FRAME data. Using scan tool, read MISFIRE CUR # display for each cylinder. If MISFIRE CUR # is increasing (indicating a misfire currently occurring) for any cylinder, go to next step. If MISFIRE CUR # is not increasing, go to DIAGNOSTIC AIDS.
4. If MISFIRE HIST # displays a very large number for more than one cylinder, go to next step. If MISFIRE HIST # does not display a very large number for more than one cylinder, go to step 14).
5. Check vacuum hoses for splits, kinks, or improper connections. If a problem is found, repair as necessary. After repairs, go to step 30). If no problem is found, go to next step.
6. Check PCV valve for improper installation or damaged "O" rings. If a problem is found, repair as necessary. After repairs, go to step 30). If no problem is found, go to next step.
7. Check throttle body inlet screen for blockage or foreign objects which may partially block airflow sample through MAF sensor. If a problem is found, repair as necessary. After repairs, go to step 30). If no problem is found, go to next step.
8. Check fuel pressure. See FUEL SYSTEM in SYSTEM/COMPONENT TESTS - 3.1L article. If a problem is found, repair as necessary. After repairs, go to step 30). If no problem is found, go to next step.
9. Check for fuel contamination. If fuel is contaminated, repair condition causing contamination. After repairs, go to step 30). If fuel is okay, go to next step.
10. Check PCM power and sensor grounds for clean and tight connection, and for proper location. If a problem is found, repair as necessary. After repairs, go to step 30). If no problem is found, go to next step.
11. Disconnect MAF sensor harness connector. Operate vehicle within conditions noted in FREEZE FRAME data. Using scan tool, read MISFIRE CUR # display for each cylinder. If MISFIRE CUR # is increasing (indicating a misfire currently occurring) for any cylinder, go to next step. If MISFIRE CUR # is not increasing, go to step 27).
12. Check intake manifold, injector "O" rings, EGR adapter, EGR valve, and EGR feed pipes for vacuum leaks. If a problem is found, repair as necessary. After repairs, go to step 30). If no problem is found, go to next step.
13. Remove EGR valve and inspect valve, seat and passages for damage. Inspect valve pintle to ensure it is not sticking partially open. If a problem is found, repair as necessary. After repairs, go to step 30). If no problem is found, go to next step.
14. Check for proper injector operation. Install Adaptor Harness(J 34730-380 & J 34730-385) to 10-pin fuel injector harness connector. Attempt to start engine. If all LEDs for cylinders No. 1-6 flash, go to next step. If not all LEDs for cylinders No. 1-6 flash, go to step 16).
15. Check for proper injector operation. See INJECTOR CIRCUIT TEST under FUEL SYSTEM DIAGNOSIS in BASIC TESTING - 3.1L article. If a problem is found, repair as necessary. After repairs, go to step 30). If no problem is found, go to step 17).
16. Check affected injector circuit(s) from PCM for open, shorted to ground, or for poor connection. Repair as necessary. After repairs, go to step 30). If circuits are okay, go to step 29).
17. Check ignition wire(s) associated with cylinder(s) that is misfiring. If a problem is found, repair as necessary. After repairs, go to step 30). If no problem is found, go to next step.
18. Install a spark tester on spark plug wire at spark plug end for cylinder indicating most severe misfire. Connect a jumper wire between engine ground and companion cylinder spark plug wire at spark plug end. Companion cylinders are 1/4, 2/5, and 3/6. Crank engine and check for crisp, Blue spark at tester. Repeat procedure for each affected cylinder. If spark is okay on all cylinders, go to step 23). If spark is not okay on any cylinder, go to next step.
19. Remove ignition coil(s) associated with misfiring cylinder(s). Check ignition coils for cracks or carbon tracking. If a problem is found, replace damaged coil(s). After repairs, go to step 30). If no problem is found, go to next step.
20. Check ignition coil secondary resistance. If resistance is not 5000-8000 ohms, replace ignition coil. After replacing ignition coil, go to step 30). If resistance is as specified, go to next step.
21. Remove ignition wire(s) associated with misfiring cylinder(s). Check ignition wire(s) boot for carbon tracking or damaged insulation. If a problem is found, replace faulty ignition wire(s). After repairs, go to step 30). If no problem is found, go to next step.
22. Check resistance of ignition wire(s) associated with misfiring cylinder(s). If resistance is greater than 30,000 ohms, replace ignition wire(s). After replacing wire(s), go to step 30). If resistance is not greater than 30,000 ohms, go to step 28).
23. Remove spark plug(s) associated with misfiring cylinder(s). Check spark plugs for excessive fouling. If spark plugs are excessively fouled, diagnose and repair mechanical engine problem. If spark plugs are not excessively fouled, go to next step.
24. Check spark plug insulation for cracks, carbon tracking or other damage. If a problem is found, replace faulty spark plug(s). After replacing spark plug(s), go to step 30). If no problem is found, go to next step.
25. Diagnose mechanical engine problem. If a problem is found, repair as necessary. After repairs, go to step 30). If no problem is found, go to next step.
26. Check for transmission DTCs. See the AUTO TRANS DIAGNOSIS article in the AUTO TRANS DIAGNOSIS section. If a problem is found, repair as necessary. After repairs, go to step 30). If no problem is found, see DIAGNOSTIC AIDS.
27. Replace MAF sensor. After replacing sensor, go to step 30).
28. Replace ignition control module. After replacing module, go to next step.
29. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
30. Using scan tool, read and record FREEZE FRAME data. Clear DTCs. Start engine and allow it to idle. Operate vehicle within conditions noted in FREEZE FRAME data. Using scan tool, read MISFIRE CUR # display for each cylinder. If MISFIRE CUR # is increasing (indicating a misfire currently occurring) for any cylinder, repeat step 2). If MISFIRE CUR # is not increasing, repair is complete.

Check secondary ignition wires. Check for damaged or faulty ignition coil. Substitute a known-good ignition coil. Check system grounds. Check MAF sensor, air induction system, fuel pressure, injectors, and EGR valve.

Extended idle periods or short trip driving could leave deposits on HO2S. Deposits could cause HO2S to respond slowly, affecting fuel control and causing misfire at idle.

DTC P0325 - KNOCK SENSOR MODULE CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Knock Sensor (KS) module is integrated in PCM circuit. KS module reads KS to determine if excessive detonation (knock) is present. If excessive knock is present, PCM will retard timing until knock goes away. When KS module is missing or malfunctioning, PCM will set DTC P0325.

Conditions for setting DTC

1. No CKP, CMP, ECT, MAF, TP or VSS DTCs set.
2. Engine speed 1000-5000 RPM.
3. Throttle angle greater than 10 percent.
4. Engine load greater than 55 percent.
5. ECT greater than 167°F (75°C).
6. Maximum retard less than 15 degrees.
7. System voltage greater than 9 volts.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. If engine knock can be heard, repair engine mechanical problem before proceeding with test. Operate vehicle within conditions required to set DTC. Using scan tool, select DTC, SPECIFIC function and enter this DTC. If scan tool display shows DTC P0325 FAILED THIS IGN, go to step 4). If scan tool display does not show DTC P0325 FAILED THIS IGN, go to next step.
3. Turn ignition on, engine off. Read and record FAIL RECORDS data for DTC P0325. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P0325 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0325 FAILED THIS IGN, see DIAGNOSTIC AIDS.
4. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
5. Using scan tool, read and record FAIL RECORDS DATA, and clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, select SPECIFIC DTC INFO for DTC P0325. Monitor scan tool until DTC P0325 test runs. If scan tool displays DTC P0325 FAILED THIS IGN, repeat step 2). If scan tool does not display DTC P0325 FAILED THIS IGN, system is okay.

Check for faulty connection at PCM. Check KS connector for proper connection or damage.

DTC P0327 - KNOCK SENSOR LOW VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Knock Sensor (KS) is used to detect engine detonation (knock). If excessive knock is present, PCM will retard timing until knock goes away. When KS module in PCM determines that an abnormally high noise channel voltage exists, PCM will set DTC P0327.

Conditions for setting DTC

1. No CMP, CKP, ECT, MAF, TP or VSS sensor DTCs set.
2. ECT greater than 167°F (75°C).
3. TP angle greater than 10 percent.
4. Engine speed is 1000-5000 RPM.
5. System voltage greater than 9 volts.
6. PCM detects a KS signal voltage within the calculated average voltage range.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Operate vehicle within conditions required to set DTC. Using scan tool, select DTC, SPECIFIC function and enter DTC P0327. If scan tool displays DTC P0327 FAILED THIS IGN, go to step 4). If scan tool does not display DTC P0327 FAILED THIS IGN, go to next step.
3. Turn engine off. Turn ignition on, engine off. Read and record FAIL RECORDS data for DTC P0327. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P0327 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0327 FAILED THIS IGN, go to DIAGNOSTIC AIDS.
4. Turn ignition off. Disconnect PCM and KS connector. Check KS signal circuit between PCM and KS harness connector for open, short to voltage or short to ground. Repair as necessary. After repairs, go to step 7). If circuit is okay, go to next step.
5. Check KS signal circuit for poor terminal connection at KS. Repair as necessary. After repairs, go to step 7). If connection is okay, go to next step.
6. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
7. Read and record FAIL RECORDS data for DTC P0327. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P0327 FAILED THIS IGN, repeat step 2). If scan tool does not display DTC P0327 FAILED THIS IGN, system is okay.

Check for faulty connection at PCM or KS. Ensure KS harness is not routed too close to high-voltage wires, such as spark plug cables, ignition coils or other high-voltage components.

DTC P0336 - 24X REFERENCE SIGNAL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Ignition Control Module (ICM) produces 24X reference signal. ICM calculates 24X reference signal by filtering Crankshaft Position (CKP) sensor 24X pulses when engine is running and CKP pulses are also being received. PCM uses this information to calculate engine speed and CKP at engine speeds less than 1200 RPM. PCM compares number of 24X reference pulses to 3X reference pulses and Camshaft Position (CMP) pulses. If PCM receives incorrect number of pulses, DTC P0336 will set.

Conditions required to set DTC are

1. Engine running and PCM receiving 3X reference pulses.
2. Ratio of 24X reference pulses to 3X reference pulses received by PCM is incorrect.
3. Conditions present for 30 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Attempt to start engine. If engine starts and runs, go to next step. If engine does not start and run, see NO START DIAGNOSIS in BASIC TESTING - 3.1L article.
3. Using scan tool, clear DTC P0336. Start engine and allow it to idle for one minute. Read DTCs. If DTC P0336 resets, go to next step. If DTC does not reset, go to DIAGNOSTIC AIDS.
4. Disconnect CMP sensor connector. Using a DVOM, check voltage at Camshaft Position (CMP) sensor and Crankshaft Position (CKP) sensor feed circuit. If DVOM reads battery voltage, go to step 5). If DVOM does not read close to battery voltage, go to step 6).
5. Turn ignition off. Disconnect PCM harness connector. Turn ignition, with engine off. Using a fused jumper wire connected to battery voltage, connect jumper wire to sensor feed circuit. Check for voltage at reference signal circuit. If DVOM reads battery voltage, go to step 12). If DVOM does not read close to battery voltage, go to step 7).
6. Check for open or short to ground in sensor feed circuit. Check connection at PCM connector. Check connections at 24X CKP and CMP sensors. Repair as necessary. After repairs are complete, go to next step. If circuits are okay, go to step 8).
7. Check connections at PCM and replace terminals as necessary. After repairs, go to step 15). If terminals are okay, go to next step.
8. Check reference signal circuit connections at CKP sensor. Replace terminals as necessary. After repairs, go to step 15). If terminals are okay, go to next step.
9. Check reference signal circuit for open or short to ground. Repair as necessary. After repairs, go to step 15). If circuit is okay, go to next step.
10. Disconnect 24X reference circuit to CKP and CMP sensors. Using DVOM, check continuity between CMP sensor harness reference low to CKP harness reference low circuit. Check continuity between CKP harness reference low circuit and PCM. If DVOM reads continuity (zero ohms) on both tests, go to step 12). If continuity does not exists, go to next step.
11. Check for open in circuits, or faulty connections at PCM or sensors. Repair as necessary. After repairs, go to step 15).
12. Turn ignition off. Disconnect 24X CKP sensor connector. Turn ignition on. Using a test light connected to battery voltage, probe reference low circuit at harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 14).
13. Replace 24X CKP sensor. After replacing sensor, go to step 14).
14. Check connections to PCM. If connections are okay, replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
15. Read and record FAIL RECORDS data for DTC P0336. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P0336 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P0336 FAILED THIS IGN, repair is complete.

Check for incorrect harness routing near secondary ignition components, ignition coil arcing to wiring harness or ICM. Check ignition coils for cracks, carbon tracking or other signs of damage. Check for secondary ignition wire(s) arcing to wiring harness.

Check for faulty connections or damaged harness. Observe a voltmeter connected to 24X CKP sensor reference circuit at PCM harness connector while moving all related harness and connectors. A change in voltage indicates fault location.

DTC P0341 - CAMSHAFT POSITION SENSOR CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

DTC P0341 will set if Camshaft Position (CMP) sensor pulses are not in proper ratio to 24X and 3X pulses.

Conditions required to set DTC are

1. Engine running and PCM receiving 3X reference pulses.
2. CMP reference pulse signal not detected in every engine cycle.
3. Conditions present for 30 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Using scan tool, read and record FAIL RECORDS data for DTC P0341. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P0341 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0341 FAILED THIS IGN, see DIAGNOSTIC AIDS.
3. Turn ignition off. Disconnect PCM connectors. Connect a test light between battery voltage and PCM harness connector sensor feed circuit. If test light illuminates, leave test light connected and go to next step. If test light does not illuminate, go to step 6).
4. Disconnect CMP sensor connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 11).
5. Check for short to ground in CMP and 24X CKP sensors feed circuit. Repair as necessary. After repairs, go to step 14). If circuit is okay, see DIAGNOSTIC AIDS.
6. Connect a fused jumper wire between PCM harness connector sensor feed circuit and battery voltage. Using a DVOM, check voltage between engine ground and PCM harness connector CMP signal circuit. If voltage is near battery voltage, leave fused jumper wire connected and go to next step. If voltage is not near battery voltage, go to step 8).
7. Check voltage between engine ground and PCM harness connector sensor ground circuit. If voltage is near battery voltage, go to step 12). If voltage is not near battery voltage, go to step 10).
8. Check for open CMP sensor feed circuit. If circuit is open, repair as necessary. After repairs, go to step 14). If circuit is okay, go to next step.
9. Check for open or short in CMP sensor signal circuit. Repair as necessary. After repairs, go to step 14). If circuit is okay, go to step 11).
10. Check for open CMP sensor ground circuit. Repair as necessary. After repairs, go to step 14). If circuit is okay, go to next step.
11. Replace CMP sensor. After replacing sensor, go to step 14).
12. Check for faulty connections at PCM. If a faulty connection is found, repair as necessary. After repairs, go to step 14). If connections are okay, go to next step.
13. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
14. Read and record FAIL RECORDS data for DTC P0336. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P0336 FAILED THIS IGN, repeat step 2). If scan tool does not display DTC P0336 FAILED THIS IGN, repair is complete.

Check for incorrect harness routing near secondary ignition components, ignition coil arcing to wiring harness or ICM. Check ignition coils for cracks, carbon tracking or other signs of damage. Check for secondary ignition wire(s) arcing to wiring harness.

Check for faulty connections or damaged harness. Observe a voltmeter connected to CMP sensor signal circuit at PCM harness connector while moving all related harness and connectors. A change in voltage indicates fault location.

DTC P0401 - EGR SYSTEM INSUFFICIENT FLOW

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

PCM tests Exhaust Gas Recirculation (EGR) valve during deceleration by momentarily commanding EGR valve on while monitoring engine MAP. PCM will illuminate MIL and store DTC P0401 if expected increase in MAP is not seen under certain conditions during deceleration.

Conditions required to set DTC are

1. No CKP, ECT, EGR pintle position, IAT, MAP, or TP sensor DTCs set.
2. No misfire or VSS DTCs set.
3. BARO is greater than 65 kPa.
4. ECT greater than 180°F (80°C).
5. Engine speed is 800-1500 RPM.
6. IAC position steady.
7. Vehicle speed greater than 25 MPH.
8. TP angle less than one percent.
9. Commanded state of A/C relay is steady.
10. MAP changes monitored during EGR flow test indicate insufficient EGR flow.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Inspect exhaust system for modifications or leaks. If a problem is found, repair as necessary and go to step 5). If no problem is found, go to next step.
3. Remove EGR valve and check pintle, valve and passages and adapter for excessive deposits or restriction. Check EGR valve gasket and pipes for leaks. If a problem is found, repair as necessary. After repairs, go to step 5). If no problem is found, go to next step.
4. Remove EGR inlet and outlet pipes from exhaust and intake manifolds. Inspect manifold EGR ports and pipes for blockage or damage. If a problem is found, repair as necessary. After repairs, go to next step. If no problem is found, see DIAGNOSTIC AIDS.
5. Read and record FAIL RECORDS data for DTC P0401. Clear DTCs and monitor EGR TEST COUNT while operating vehicle within conditions noted in DIAGNOSTIC AIDS until 9-12 test samples have been taken. Read SPECIFIC DTC. If scan tool displays DTC P0401 TEST RAN AND PASSED, repair is complete. If scan tool does not display DTC P0401 TEST RAN AND PASSED, return to step 2).

PCM will only run EGR flow test during gradual deceleration, a closed throttle condition and with vehicle speed greater than 20 MPH. Accelerate vehicle to greater than 20 MPH, and gradually decelerate 9-13 times.

Check for faulty connections or damaged harness. Inspect PCM harness connector EGR control circuit for backed-out terminal. Observe ACTUAL EGR POSITION display on scan tool while moving all related harness and connectors. A change in scan tool display indicates fault location.

If EGR valve shows signs of excessive heat, check exhaust system for blockage or plugged catalytic converter.

DTC P0403 - EGR SOLENOID CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

PCM monitors EGR valve pintle position input to ensure that valve responds properly to commands from PCM. The EGR (linear) valve is controlled by using an ignition positive driver and ground circuit within the PCM. The driver has the ability to detect an electrical malfunction in the ignition voltage or ground circuit, then signal the PCM to set the DTC.

Conditions for setting this DTC

1. Ignition switch in CRANK or RUN positions.
2. No CKP, ECT, IAT, MAF, MAP, TP, VSS sensors, misfire, idle speed or fuel injector related DTCs set.
3. System voltage at 10-16 volts.
4. EGR feedback is .4 volt greater than EGR closed valve pintle position when EGR is commanded to zero percent.
5. Conditions present for longer than 20 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Start and operate engine at idle. Using scan tool, observe actual EGR position. If actual EGR position is zero percent, go to next step. If actual EGR position is not zero percent, go to step 9).
3. Turn ignition on, engine off. Using scan tool select EGR VALVE OUTPUT CONTROL function. Increment EGR valve through all positions while comparing DESIRED EGR POSITION to ACTUAL EGR POSITION. If desired EGR position remains close to actual EGR position at all commanded positions, go to next step. If EGR position is not as specified, go to step 5).
4. Using scan tool, review FAIL RECORDS data. Operate vehicle within FAIL RECORDS conditions and monitor SPECIFIC DTC info. If scan tool indicates that DTC P0403 failed this ignition cycle, go to next step. If scan tool does not indicate that DTC P0403 failed in this ignition cycle, see DIAGNOSTIC AIDS.
5. Disconnect EGR valve harness connector. Using a test light, connect test light between EGR ground and control circuit at EGR harness connector. Using scan tool, command EGR valve to 100 percent. If test light illuminates, go to step 10). If test light does not illuminate, go to next step.
6. Using test light connected to battery voltage, probe EGR ground circuit at EGR harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 14).
7. Probe EGR control circuit at EGR harness connector. If test light illuminates, go to step 13). If test light does not illuminate, go to next step.
8. Turn ignition off. Disconnect PCM harness connector. Check for open in EGR control circuit at PCM connector. Repair as necessary. After repairs, go to step 21). If circuit is okay, go to step 19).
9. Turn ignition off. Disconnect PCM harness connector. Turn ignition on, engine off. Using test light connected to ground, probe EGR control circuit at PCM connector. If test light illuminates, go to step 12). If test light does not illuminate, go to step 20).
10. Check for poor terminal contact at EGR valve. Repair as necessary. After repairs, go to step 21). If terminals are okay, go to next step.
11. Replace EGR valve. After replacing EGR valve, go to step 21).
12. Locate and repair short to voltage in EGR valve control circuit. After repairs, go to step 21).
13. Turn ignition off. Disconnect PCM harness connector. Using a test light connected to battery voltage, probe EGR control circuit at EGR harness connector. If test light illuminates, go to step 18). If test light does not illuminate, go to step 17).
14. Turn ignition off. Disconnect PCM harness connector. Using a test light connected to ground, probe EGR ground circuit at EGR harness connector. If test light illuminates, go to step 16). If test light does not illuminate, go to next step.
15. Check for open in EGR valve ground circuit. Repair as necessary. After repairs, go to step 21). If circuit is okay, go to step 20).
16. Locate and repair short to voltage in EGR valve ground circuit. After repairs, go to step 21).
17. Check EGR valve control circuit for short to EGR ground circuit. Check for short between EGR valve control circuit and EGR pintle position sensor. Repair as necessary. After repair, go to step 21). If circuits are okay, go to step 20).
18. Locate and repair short to ground in EGR valve control circuit. After repairs, go to step 21).
19. Check circuits related to EGR valve for poor terminal connection at PCM. Repair as necessary. After repairs, go to step 21). If terminal connections are okay, go to next step.
20. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
21. Using scan tool, select DTC, CLEAR INFO function. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter DTC P0404. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool did not indicate that this test ran and passed, repeat step 2).

Check for poor connection at PCM or EGR valve harness connectors.

DTC P0404 - EGR SYSTEM PERFORMANCE

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

PCM monitors EGR valve pintle position input to ensure that valve responds properly to commands from PCM. PCM compares actual EGR position with desired EGR position when valve is commanded open. If actual EGR position is 15 percent less than desired EGR position when PCM is commanding EGR valve opened, DTC will set.

Conditions for setting DTC

1. No CKP, ECT, IAT, MAF, MAP, TP, VSS sensor, idle speed, fuel injector, misfire DTCs set.
2. System voltage is 10-16 volts.
3. Actual EGR position is 15 percent less than desired EGR position.
4. Conditions present for longer than 20 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Turn ignition on. Using scan tool, check if DTC P0403 or P0405 is present. If any of this DTC is present, diagnose affected DTC first. If DTC P0403 or P0405 is not present, select EGR OUTPUT CONTROL function. Increment EGR valve through all positions while comparing desired to actual EGR position. If desired and actual EGR position remains close to each other at all commanded positions, go to next step. If desired and actual EGR position is not within range, go to step 4).
3. Using scan tool, review FAIL RECORDS data. Operate vehicle within FAIL RECORDS conditions and monitor SPECIFIC DTC info. If scan tool indicates that this DTC failed this ignition cycle, go to next step. If scan tool does not indicate that this DTC failed in this ignition cycle, see DIAGNOSTIC AIDS.
4. Disconnect EGR valve harness connector. Check voltage between EGR pintle position sensor ground circuit and 5-volt reference circuit at EGR harness connector. If voltage reads 5 volts, go to next step. If voltage does not read 5-volts, go to step 10).
5. Using test light connected to battery voltage, probe EGR pintle position signal circuit at EGR harness connector. If test light illuminates, go to step 8). If test light does not illuminate, go to next step.
6. Using a fused jumper wire, jumper EGR 5-volt reference circuit and EGR pintle position signal circuit at EGR harness connector. Using scan tool, observe actual EGR position. If actual EGR position is 100 percent, go to step 9). If actual EGR position is not 100 percent, go to next step.
7. Turn ignition off. Disconnect PCM harness connector. Check for open in EGR pintle position signal circuit. Repair as necessary. After repairs, go to step 17). If circuit is okay, go to step 15).
8. Turn ignition off. Disconnect PCM harness connector. Using a test light connected to battery voltage, probe EGR pintle position signal circuit. If test light illuminates, go to step 13). If test light does not illuminate, go to step 14).
9. Check for poor terminal connections at EGR valve. Repair as necessary. After repairs, go to step 17). If terminal connections are okay, go to step 12).
10. Check 5-volt reference circuit for open between EGR and PCM. Check 5-volt reference circuit for short to ground. Repair as necessary. After repairs, go to step 17). If circuits are okay, go to next step.
11. Check EGR pintle position ground sensor circuit for open or short to voltage. Repair as necessary. After repairs, go to step 17). If circuit is okay, go to step 15).
12. Replace EGR valve. After replacing EGR valve, go to step 17).
13. Locate and repair short to ground in EGR pintle position signal circuit. After repairs, go to step 17).
14. Check for short in EGR pintle position signal circuit to sensor ground. Repair as necessary. After repairs, go to step 17). If circuit is okay, go to step 16).
15. Check circuits related to EGR valve for poor terminal connection at PCM. Repair as necessary. After repairs, go to step 17). If circuits are okay, go to next step.
16. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
17. Using scan tool, select DTC, CLEAR INFO function. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter DTC P0404. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool did not indicate that this test ran and passed, repeat step 2).

Check for excessive deposits on EGR valve pintle or seat. Check for poor connection at PCM or EGR valve harness connectors.

DTC P0405 - EGR SENSOR CIRCUIT LOW VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

PCM monitors EGR valve pintle position input to ensure that valve responds properly to commands from PCM. PCM compares actual EGR position with desired EGR position when valve is commanded open. If actual EGR position is 15 percent less than desired EGR position when PCM is commanding EGR valve opened, DTC will set.

Conditions for setting DTC

1. No ECT, HO2S, IAT, MAF or TP sensor DTCs set.
2. Engine run time met. Time ranges from 45 seconds to 8.5 minutes depending upon ECT at start-up.
3. TP angle greater than 2 percent.
4. System voltage greater than 10 volts.
5. EGR feedback is less than .14 volt at anytime.
6. Conditions present for longer than 20 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Turn ignition on. Using scan tool, select EGR OUTPUT CONTROL function. Increment EGR valve through all positions while comparing desired to actual EGR position. If desired and actual EGR position remains close to each other at all commanded positions, go to next step. If desired and actual EGR position is not within range, go to step 4).
3. Using scan tool, review FAIL RECORDS data. Operate vehicle within FAIL RECORDS conditions and monitor SPECIFIC DTC info. If scan tool indicates that this DTC failed this ignition cycle, go to next step. If scan tool does not indicate that this DTC failed in this ignition cycle, see DIAGNOSTIC AIDS.
4. Disconnect EGR valve harness connector. Check voltage between EGR pintle position sensor ground circuit and 5-volt reference circuit at EGR harness connector. If voltage reads 5 volts, go to next step. If voltage does not read 5-volts, go to step 9).
5. Using test light connected to battery voltage, probe EGR pintle position signal circuit at EGR harness connector. If test light illuminates, go to step 8). If test light does not illuminate, go to next step.
6. Using a fused jumper wire, jumper EGR 5-volt reference circuit and EGR pintle position signal circuit at EGR harness connector. Using scan tool, observe actual EGR position. If actual EGR position is 100 percent, go to step 13). If actual EGR position is not 100 percent, go to next step.
7. Turn ignition off. Disconnect PCM harness connector. Check for open in EGR pintle position signal circuit. Repair as necessary. After repairs, go to step 19). If circuit is okay, go to step 17).
8. Turn ignition off. Disconnect PCM harness connector. Using a test light connected to battery voltage, probe EGR pintle position signal circuit. If test light illuminates, go to step 12). If test light does not illuminate, go to step 15).
9. Using test light connected to battery voltage, probe EGR 5-volt reference circuit. If test light illuminates, go to next step. If test light does not illuminate, go to step 11).
10. Turn ignition off. Disconnect PCM harness connector. Using test light connected to battery voltage, probe EGR 5-volt reference circuit. If test light illuminates, go to step 16). If test light does not illuminate, go to step 18).
11. Check 5-volt reference circuit for open between EGR and PCM. Repair as necessary. After repairs, go to step 19). If circuits are okay, go to step 17).
12. Locate and repair short to ground in EGR valve pintle position circuit. After repairs, go to step 19).
13. Check for poor terminal connections at EGR valve. Check for short in EGR pintle position signal circuit to control circuit. Repair as necessary. After repairs, go to step 19). If circuits are okay, go to next step.
14. Replace EGR valve. After replacing EGR valve, go to step 19).
15. Check for short in EGR pintle position signal circuit to sensor ground. Repair as necessary. After repairs, go to step 19). If circuit is okay, go to step 18).
16. Locate and repair short to ground in 5-volt reference circuit. After repairs, go to step 19).
17. Check circuits related to EGR valve for poor terminal connection at PCM. Repair as necessary. After repairs, go to step 19). If circuits are okay, go to next step.
18. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
19. Using scan tool, select DTC, CLEAR INFO function. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter DTC P0404. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this test ran and passed, system is okay. If scan tool does not indicate that this test ran and passed, repeat step 2).

Check for excessive deposits on EGR valve pintle or seat. Check for poor connection at PCM or EGR valve harness connectors.

Three-Way Catalyst (TWC) system is used to control emission. PCM uses signal from Heated Oxygen Sensors (HO2S) to read efficiency of TWC. PCM will set DTC P0420 if TWC oxygen storage capacity is less than a predetermined threshold.

Conditions required to set DTC are

1. No CKP, ECT, HO2S, IAT, MAF, MAP, or TP sensor DTCs set.
2. No EGR pintle position, EVAP purge, fuel trim, injector circuit, misfire or VSS DTCs set.
3. Converter warm-up test passed.
4. Engine speed 1000-3000 RPM.
5. Vehicle speed 30-75 MPH.
6. PCM determines TWC oxygen storage capacity less than predetermined threshold.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Diagnose any other DTCs before proceeding. If no other DTCs are set, go to next step.
3. Using scan tool, clear DTCs. Ensure A/C is off. Start and warm engine to normal operating temperature. Operate vehicle within the conditions for setting this DTC. Test may need to be performed up to 6 times in order to pass or fail. If test has been performed or attempted for more than 6 times and DTC has not passed or failed this ignition cycle, test may be aborting. See DIAGNOSTIC AIDS. If scan tool indicates that DTC ran and passed in this ignition cycle, system is okay. If scan tool does not indicate that DTC ran and passed in this ignition cycle, go to next step.
4. Ensure TWC is an original equipment part. Check TWC for dents or discoloration caused by excessive heat. Ensure no internal damaged catalyst rattle exists. If a problem is found, repair as necessary. After repairs, go to step 9). If no problem is found, go to next step.
5. Check exhaust system for leaks, damage, loose or missing hardware. If a problem is found, repair as necessary. After repairs, go to step 7). If no problems are found, go to next step.
6. Ensure HO2S 2 is securely installed and that harness is not damaged or contacting exhaust. If a problem is found, repair as necessary. After repairs, go to step 8). If no problems are found, go to step 9).
7. Repair exhaust system. After repairs, go to step 10).
8. Repair HO2S sensor circuit. After repairs, go to step 10).
9. Replace TWC. Check for possible engine misfire DTC or engine mechanical problem. After repairs, go to next step.
10. Using scan tool, clear DTCs. Ensure A/C is off. Start and warm engine to normal operating temperature. Operate vehicle within the conditions for setting this DTC. Test may need to be performed up to 6 times in order to pass or fail. If test has been performed or attempted for more than 6 times and DTC has not passed or failed this ignition cycle, test may be aborting. See DIAGNOSTIC AIDS. If scan tool indicates that DTC ran and passed in this ignition cycle, go to next step. If scan tool does not indicate that DTC ran and passed in this ignition cycle, repeat step 2).
11. If additional DTCs are present, diagnose affected DTCs. If no additional DTCs are present, system okay.

PCM will not enable the catalyst test if

1. Engine speed is plus or minus 100 RPM from desired idle speed.
2. TP is zero percent.
3. Short term integrator is between -20 percent and +20 percent.

The catalyst test will abort if vehicle falls out of following the conditions

1. Engine speed is plus or minus 125 RPM from desired idle speed.
2. TP is zero percent.
3. Short term integrator is between -20 percent and +20 percent.

The catalyst test may abort due to change in engine load (i.e., A/C, cooling fan on). If this problem occurs, use scan tool to force cooling fans to turn on, then repeat test.

Check for faulty connections or damaged harness. Inspect PCM harness connector EGR control circuit for backed-out terminal. Observe scan tool while moving all related harness and connectors. A change in scan tool display indicates fault location.

DTC P0440 - EVAP SYSTEM

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Evaporative leak detection strategy is based on applying vacuum to EVAP system and monitoring vacuum decay. Powertrain Control Module (PCM) monitors vacuum level by means of fuel tank vacuum sensor input. At a predetermined time, EVAP purge solenoid and EVAP vent solenoid are turned on. This allows engine vacuum to draw a small vacuum on entire EVAP system. Whenever a sufficient vacuum level cannot be achieved, a large leak or faulty EVAP purge solenoid is indicated.

Conditions for setting this DTC are as follows

1. No TP sensor, ODM, IAT sensor, or MAP sensor DTCs present.
2. Start-up ECT 40-86°F (4-30°C).
3. Start-up ECT not greater than 14°F (8°C) greater than start-up IAT.
4. Start-up IAT not greater than 4°F (2°C) of start-up ECT.
5. Fuel tank level is 15-85 percent.
6. BARO is greater than 75 kPa.
7. Vehicle has been driven at least 11 miles.
8. EVAP system is unable to achieve or maintain vacuum during diagnostic test.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Check if DTC P1665 or P1676 is also set. If any of DTCs is present, diagnose affected DTCs. If DTCs are not present, go to next step.
3. Turn ignition off. Remove fuel filler cap. Turn ignition on. Using scan tool, observe fuel tank pressure. If fuel tank pressure is zero in. H2O, go to next step. If fuel tank pressure in not zero in. H2O, diagnose evaporative system.
4. Replace fuel filler cap. Using scan tool, capture FAIL RECORD data for DTC P0440 and clear DTC. Command EVAP vent solenoid on. Connect EVAP Pressure/Purge Diagnostic Station (J 41413) to EVAP service port. Pressurize EVAP system using diagnostic station. Monitor pressure on EVAP pressure gauge on diagnostic station. If pressure is 5 in. H2O, go to next step. If pressure is not 5 in. H2O, go to step 6).
5. Maintain EVAP pressure at 5 in. H2O. Observe fuel tank pressure on scan tool. If fuel tank pressure reading on scan tool is 5 in. H2O, go to step 8). If reading is not 5 in. H2O, go to next step.
6. Disconnect fuel tank vapor line and EVAP purge line from EVAP canister. Block canister fitting for fuel tank pressure line. Connect a hand-held vacuum pump to canister fitting for EVAP purge line. Ensure that EVAP vent solenoid is still commanded on. Apply vacuum to EVAP canister. If vacuum can be maintained at 5 in. Hg, go to step 11). If vacuum cannot be maintained at 5 in. Hg, go to step 10).
7. Check for restriction in fuel tank vapor line or EVAP purge line. Repair as necessary. After repairs, go to step 16). If restriction is not found, diagnose EVAP system.
8. Disconnect vacuum source line at EVAP purge solenoid and plug vacuum source fitting on solenoid. Using scan tool's output tests function, select and activate SYSTEM PERF. Pressurize EVAP system to 5 in H2O. Observe EVAP pressure gauge on diagnostic station while removing plug from EVAP purge solenoid vacuum source fitting. If EVAP pressure decreases to zero in. H2O within 15 seconds while system performance is activated, go to next step. If EVAP pressure does not decrease to zero in. H2O within 15 seconds, go to step 13).
9. Install vacuum gauge on EVAP diagnostic station to vacuum source line. Start and operate engine to greater than 2000 RPM. Observe source vacuum level. If vacuum level is greater than -15 in. Hg, see DIAGNOSTIC AIDS. If vacuum level is not greater than -15 in. Hg, go to step 14).
10. Check for disconnected or damaged vent hose. Check for damaged EVAP canister. Repair as necessary. After repairs, go to step 16). If no problems are found, go to next step.
11. Check for faulty or missing fuel filler cap. Check for disconnected or leaking fuel tank vapor line. Check for disconnected or damaged EVAP purge line. If problem is found, repair as necessary. After repairs, go to step 16). If no problems are found, go to next step.
12. Using scan tool, command EVAP vent solenoid on. Continuously attempt to pressurize the EVAP system by leaving the EVAP diagnostic station control knob in the pressurized position. Using the Ultrasonic Leak Detector (J 41416), locate and repair leak in EVAP system. After repairs, go to step 16).
13. Replace EVAP purge solenoid. After replacing solenoid, go to step 16).
14. Check for carbon release into the EVAP system. Repair as necessary. After repairs, go to step 16).
15. Replace EVAP vent solenoid. After replacing solenoid, go to next step.
16. Turn ignition on. Using scan tool, command EVAP vent solenoid on. Using EVAP diagnostic station, pressurize EVAP system to 15 in. H2O. Move rotary switch in diagnostic station to HOLD and observe EVAP pressure gauge. If EVAP pressure decreases to less than 10 in. Hg within 2 minutes, repeat step 3). If EVAP pressure does not decrease, system is okay.

Check for the following

1. Cracked or punctured EVAP canister.
2. Damaged or disconnected source vacuum line, EVAP purge line, vent hose, for fuel tank vapor line.
3. Poor connection at PCM.
4. Inspect harness connectors for backed-out terminals, improper mating, broken lock, damaged terminals, or poor wire connection.
5. Check for intermittent in circuit.
6. Check for kinked, pinched or plugged vacuum lines to EVAP purge or fuel tank vapor line. Also check for restrictions.
7. Faulty or damaged evaporative canister.

DTC P0442 - EVAP CONTROL SYSTEM (SMALL LEAK DETECTED)

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Evaporative (EVAP) emission system includes the following components, fuel tank, EVAP vent solenoid, fuel tank pressure sensor, fuel pipes and hoses, fuel cap, EVAP lines, EVAP canister and EVAP purge solenoid.

The evaporative leak detection diagnostic strategy is based on applying vacuum to EVAP system and monitoring vacuum decay. PCM monitors vacuum level through the fuel tank pressure sensor input. At a given time, the EVAP purge solenoid and EVAP vent solenoid are turned on, allowing engine vacuum to draw a small vacuum on the entire evaporative emission system. After desired vacuum level has been achieved, the EVAP purge solenoid is turned off, sealing the system. A leak is detected by monitoring for a decrease in vacuum level over a given time period, all other variables remaining constant. A small leak in the system will cause DTC to set.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Check if DTC P1665 or P1676 is also set. If any of DTC(s) is present, diagnose affected DTC(s). If DTCs are not present, go to next step.
3. Turn ignition off. Remove fuel filler cap. Turn ignition on. Using scan tool, observe fuel tank pressure. If fuel tank pressure is zero in. H2O, go to next step. If fuel tank pressure in not zero in. H2O, diagnose evaporative system.
4. Replace fuel filler cap. Using scan tool, capture FAIL RECORD data for DTC P0440 and clear DTC. Command EVAP vent solenoid on. Connect EVAP Pressure/Purge Diagnostic Station (J 41413) to EVAP service port. Pressurize EVAP system using diagnostic station. Monitor pressure on EVAP pressure gauge on diagnostic station. If pressure is 5 in. H2O, go to next step. If pressure is not 5 in. H2O, go to step 6).
5. Turn ignition on, with engine off. Using scan tool, command EVAP vent solenoid on. Using diagnostic station, pressurize EVAP system to 15 in. H2O and monitor pressure on EVAP pressure gauge on diagnostic station. Move rotary switch on diagnostic station to HOLD position. If EVAP pressure decreases to less than 10 in. H2O within 2 minutes, go to next step. If pressure does not decrease as specified, see DIAGNOSTIC AIDS.
6. Disconnect fuel tank vapor line and EVAP purge line from EVAP canister. Block canister fitting for fuel tank pressure line. Connect a hand-held vacuum pump to canister fitting for EVAP purge line. Ensure that EVAP vent solenoid is still commanded on. Apply vacuum to EVAP canister. If vacuum can be maintained at 5 in. Hg, go to step 9). If vacuum cannot be maintained at 5 in. Hg, go to next step.
7. Check for disconnected or damaged vent hose. Check for damaged EVAP canister. Repair as necessary. After repairs, go to step 11). If no problems were found, go to next step.
8. Replace EVAP purge solenoid. After replacing EVAP solenoid, go to step 11).
9. Check for faulty or missing fuel filler cap. Check for disconnected or leaking fuel tank vapor line. Check for disconnected or damaged EVAP purge line. If problem is found, repair as necessary. After repairs, go to step 11). If no problems were found, go to next step.
10. Using scan tool, command EVAP vent solenoid on. Continuously attempt to pressurize the EVAP system by leaving the EVAP diagnostic station control knob in the pressurized position. Using the Ultrasonic Leak Detector (J 41416), locate and repair leak in EVAP system. After repairs, go to next step.
11. Turn ignition on. Using scan tool, command EVAP vent solenoid on. Using EVAP diagnostic station, pressurize EVAP system to 15 in. H2O. Move rotary switch in diagnostic station to HOLD position and observe EVAP pressure gauge. If EVAP pressure decreases to less than 10 in. Hg within 2 minutes, repeat step 3). If EVAP pressure does not decrease, system is okay.

Check for the following

1. Cranked and punctured EVAP canister.
2. Damaged or disconnected source vacuum line, EVAP purge line, vent hose, for fuel tank vapor line.
3. Poor connection at PCM.
4. Inspect harness connectors for backed-out terminals, improper mating, broken lock, damaged terminals, or poor wire connection.
5. Check for intermittent in circuit.
6. Check for kinked, pinched or plugged vacuum lines to EVAP purge or fuel tank vapor line. Also check for restrictions.
7. Faulty or damaged evaporative canister.

DTC P0446 - EVAP CANISTER VENT BLOCKED

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Evaporative (EVAP) emission system includes the following components, fuel tank, EVAP vent solenoid, fuel tank pressure sensor, fuel pipes and hoses, fuel cap, EVAP lines, EVAP canister and EVAP purge solenoid.

A restricted or blocked EVAP vent path is detected by monitoring fuel tank pressure during normal operation (EVAP vent solenoid open, EVAP purge solenoid normal). With the EVAP vent solenoid open, vacuum level in the system should be very low, unless the vent path is blocked. A blockage can caused by the following conditions

1. Faulty EVAP vent solenoid (stuck closed).
2. Plugged, kinked or pinched vent hose.
3. Shorted EVAP vent solenoid driver circuit.
4. Plugged evaporative canister.

An incorrect fuel tank pressure sensor signal is detected by monitoring fuel tank pressure when ignition is first turned on during a cold start. If fuel tank pressure signal is out of range, EVAP diagnostic will not be able to detect leaks. If any of the conditions described are present, DTC P0446 will set.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Check if DTC P1676 is also set. If DTC P1676 is present, diagnose DTC first. If DTC P1676 is not present, go to next step.
3. Turn ignition on. Using scan tool, capture FAIL RECORD data for DTC P0446 and clear DTC. Turn ignition off. Remove fuel filler cap. Using scan tool, observe fuel tank pressure on scan tool. If fuel tank pressure is zero in. Hg, go to next step. If fuel tank pressure is not zero in. Hg, diagnose EVAP control system.
4. Replace fuel filler cap. Using scan tool, command EVAP vent solenoid on. Connect EVAP Pressure/Purge Diagnostic Station (J 41413) to EVAP service port. Pressurize EVAP system using diagnostic station. Monitor pressure on EVAP pressure gauge on diagnostic station. If pressure is 5 in. H2O, go to next step. If pressure is not 5 in. H2O, diagnose EVAP control system.
5. Maintain EVAP pressure at 5 in. H2O. Using scan tool, command EVAP vent solenoid off (open) while observing EVAP pressure gauge on diagnostic station. If EVAP pressure changes to zero in. H2O within 5 seconds, see DIAGNOSTIC AIDS. If pressure does not change, go to next step.
6. Disconnect large vent hose (marked AIR) from EVAP canister. Move rotary on diagnostic station to PURGE position. Start and operate engine to normal operating temperature. Using scan tool, command purge solenoid on (open). Monitor vacuum gauge on diagnostic station for 5 seconds while holding engine speed at 2500 RPM. If vacuum remains less than -45 in. H2O, go to next step. If vacuum does not remain less than -45 in. H2O, go to step 9).
7. Check for disconnected, kinked or damaged vent hose between EVAP canister and vent solenoid. Repair as necessary. After repairs, go to step 10). If no problems were found, go to next step.
8. Replace EVAP vent solenoid. After replacing solenoid, go to step 10).
9. Replace EVAP canister. After replacing canister, go to next step.
10. Using scan tool, command EVAP vent solenoid on. Pressurize the EVAP system to 5 in. H2O. Move rotary switch in diagnostic station to HOLD and observe EVAP pressure gauge. Command EVAP vent solenoid off (open). Observe EVAP pressure on gauge. If EVAP pressure decreases to zero in. H2O within 5 seconds, system is okay. If EVAP pressure does not decrease, repeat step 3).

Check for the following

1. Poor connection at PCM.
2. Inspect harness connectors for backed-out terminals, improper mating, broken lock, damaged terminals, or poor wire connection.
3. Check for intermittent, open or shorted circuit.
4. Check for kinked, pinched or plugged vent hose.

DTC P0452 - FUEL TANK PRESSURE SENSOR LOW VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

PCM monitors fuel tank pressure sensor signal to detect vacuum decay and excess vacuum during the enhanced EVAP diagnostic. Fuel tank pressure sensor measures the difference between air pressure (or vacuum) in the tank and the outside air pressure. PCM applies 5-volt reference and ground to the sensor. Sensor will return a signal voltage between 0.1-4.9 volts. If PCM detects a fuel tank pressure sensor signal that is excessively low, DTC will set.

Conditions for setting DTC

1. Ignition on.
2. Fuel tank pressure sensor signal is less than 0.3 volt.
3. Conditions present for one second.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Turn ignition on, engine off. Monitor fuel tank pressure sensor voltage on scan tool. If scan tool reading is 0.30 volt or less, go to step 4). If scan tool reading is not 0.30 volt or less, go to next step.
3. Turn ignition on, engine off. Using scan tool, review FREEZE FRAME and/or FAILURE RECORDS data for this DTC and observe parameters. Turn ignition off for 15 seconds. Start and operate vehicle within conditions required for this DTC to run. Using scan tool, select DTC option, SPECIFIC DTC option, then enter this DTC. If scan tool indicates that this diagnostic failed this ignition cycle, go to next step. If scan tool does not indicate that this diagnostic failed this ignition cycle, see DIAGNOSTIC AIDS.
4. Disconnect fuel tank pressure sensor connector. Jumper fuel tank pressure sensor 5-volt reference circuit and signal circuit at harness connector. Using scan tool observe fuel tank pressure sensor voltage. If scan tool display reads 5 volts, go to step 8). If scan tool display does not read 5 volts, go to next step.
5. Check voltage between 5-volt reference voltage circuit and sensor ground circuit at fuel tank pressure sensor harness connector. If voltage reading is 5 volts, go to step 9). If voltage reading is not 5 volts, go to next step.
6. Turn ignition off. Disconnect PCM harness connector. Check 5-volt reference circuit for poor connection at PCM connector. Repair as necessary. After repairs, go to step 13). If connection is okay, go to next step.
7. Check fuel tank pressure sensor 5-volt reference circuit between sensor and PCM for open, short to ground, or short to sensor ground circuit. Repair as necessary. After repairs, go to step 13). If circuit is okay, go to step 12).
8. Check for poor terminal connections at fuel tank pressure sensor connector. Repair as necessary. After repairs, go to step 13). If connections are okay, go to step 11).
9. Turn ignition off. Disconnect PCM harness connector. Check fuel tank pressure signal circuit for poor connection at PCM connector. Repair as necessary. After repairs, go to step 13). If connection is okay, go to next step.
10. Check fuel tank pressure signal circuit between the fuel tank pressure sensor connector and PCM for an open, short to ground, or short to sensor ground circuit. Repair as necessary. After repairs, go to step 13). If circuit is okay, go to step 12).
11. Replace fuel tank pressure sensor. After replacing sensor, go to step 13).
12. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
13. Using scan tool, select DTC, CLEAR INFO function. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter DTC P0443. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2).

An intermittent open in the signal or 5-volt reference circuit or connectors will set DTC. Wiggle harnesses and connectors while monitoring tank pressure voltage. Review malfunction history data and attempt to reproduce the condition and fault.

DTC P0453 - FUEL TANK PRESSURE SENSOR HIGH VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

PCM monitors fuel tank pressure sensor signal to detect vacuum decay and excess vacuum during the enhanced EVAP diagnostic. Fuel tank pressure sensor measures the difference between air pressure (or vacuum) in the tank and the outside air pressure. PCM applies 5-volt reference and ground to the sensor. Sensor will return a signal voltage between 0.1-4.9 volts. If PCM detects a fuel tank pressure sensor signal that is excessively low, DTC will set.

Conditions for setting DTC

1. Ignition on.
2. Fuel tank pressure sensor signal is greater than 4.8 volt.
3. Conditions present for 5 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Turn ignition on, engine off. Monitor fuel tank pressure sensor voltage on scan tool. If scan tool reading is greater than 4.7 volts, go to step 4). If scan tool reading is not greater 4.7 volts, go to next step.
3. Turn ignition on, engine off. Using scan tool, review FREEZE FRAME and/or FAILURE RECORDS data for this DTC and observe parameters. Turn ignition off for 15 seconds. Start and operate vehicle within conditions required for this DTC to run. Using scan tool, select DTC option, SPECIFIC DTC option, then enter this DTC. If scan tool indicates that this diagnostic failed this ignition cycle, go to next step. If scan tool does not indicate that this diagnostic failed this ignition cycle, see DIAGNOSTIC AIDS.
4. Disconnect fuel tank pressure sensor connector. Using scan tool observe fuel tank pressure sensor voltage. If scan tool display reads about zero volts, go to step 6). If scan tool display is not about zero volts, go to next step.
5. Turn ignition off. Disconnect PCM harness connector. Check fuel tank pressure signal circuit for short to voltage or short to 5-volt reference circuit. Repair as necessary. After repairs, go to step 11). If connection is okay, go to step 10).
6. Turn ignition off. Disconnect PCM harness connector. Check fuel tank pressure ground circuit for poor terminal connection at PCM. Repair as necessary. After repairs, go to step 11). If connection is okay, go to next step.
7. Check for open in fuel tank pressure sensor ground circuit. Repair as necessary. After repairs, go to step 11). If circuit is okay, go to next step.
8. Check for poor terminal connections at fuel tank pressure sensor connector. Repair as necessary. After repairs, go to step 11). If connections are okay, go to next step.
9. Replace fuel tank pressure sensor. After replacing sensor, go to step 11).
10. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
11. Using scan tool, select DTC, CLEAR INFO function. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter this DTC. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2).
12. Check for additional DTCs. If additional DTCs are set, diagnose affected DTCs. If no additional DTCs are set, system is okay.

Check for damaged harness or poor connection at PCM or fuel tank pressure sensor.

DTC P0506 - IDLE CONTROL SYSTEM LOW RPM

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

PCM controls idle speed with an Idle Air Control (IAC) valve to a calculated RPM based on sensor inputs and actual engine RPM. PCM moves IAC valve in or out to vary amount of airflow into intake manifold and thus decrease or increase idle RPM.

PCM commands IAC in counts. A higher count, allows more air to by-pass throttle plate (higher idle).

Conditions required to set DTC are

1. No CKP, ECT, IAT, MAF, MAP, TP, VSS sensor DTCs set.
2. No EVAP solenoid, EVAP system, fuel trim, fuel injector, EGR flow or EGR pintle position DTCs set.
3. ECT greater than 122°F (70°C).
4. Engine running at least 2 minutes.
5. Vehicle speed less than 3 MPH.
6. IAT greater than 0°F (-18°C).
7. Throttle closed.
8. Engine speed greater than 175 RPM lower than desired idle.
9. BARO greater than 65 kPa.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Using scan tool, read DTCs. If any other DTCs are set, diagnose affected DTCs before proceeding. If no other DTCs are set, go to next step.
3. Start engine. Turn all accessories off. Using scan tool, monitor ENGINE SPEED and command engine speed up to 1500 RPM, down to 650 RPM, and up to 1500 RPM. If ENGINE SPEED remains within 50 RPM of desired RPM for each command, see DIAGNOSTIC AIDS. If ENGINE SPEED is not as specified, to next step.
4. Disconnect IAC harness connector. Install IAC Node Light (J 37027) in IAC harness connector. Monitor node lights while commanding engine speed up to 1500 RPM, down to 650 RPM, and up to 1500 RPM. Both node lights should cycle Green and Red, but not off as RPM changes from 650-1500 RPM. If lights flash as specified, go to step 6). If lights do not flash as specified, go to next step.
5. Check IAC "A" high and low, and IAC "B" high and low circuits for open, short to voltage or short to ground. If a problem is found, repair as necessary. After repairs, go to step 11). If circuits are okay, go to step 9).
6. Ensure throttle stop screw has not been tampered with. Check for stuck IAC valve or throttle linkage. Check for restrictions, collapse or blockage in air intake system, air ducts or air filter. Check throttle body bore and IAC for excessive deposits. If a problem is found, repair as necessary. After repairs, go to step 11). If no problem is found, go to next step.
7. Check for faulty connection at IAC harness connector. If faulty connection is found, repair as necessary. After repairs, go to step 11). If connection is okay, go to next step.
8. Replace IAC valve. After replacing IAC valve, go to step 11).
9. Check for faulty connection at PCM harness connector. If faulty connection is found, repair as necessary. After repairs, go to step 11). If connection is okay, go to next step.
10. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
11. Start engine. Turn all accessories off. Using scan tool, monitor ENGINE SPEED and command engine speed up to 1500 RPM, down to 500 RPM, and up to 1500 RPM. If ENGINE SPEED remains within 100 RPM of desired RPM for each command, repair is complete. If ENGINE SPEED is not as specified, return to step 2).

Check for faulty connection at IAC and PCM connectors. Check for damaged harness. Check for restrictions, collapse or blockage in air intake system, air ducts or air filter. Check throttle body bore and IAC for excessive deposits. Check for large vacuum leak, such as incorrectly installed PCV valve or disconnected brake booster hose. Check for restricted air intake system.

DTC P0507 - IDLE CONTROL SYSTEM HIGH RPM

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

The Idle Air Control (IAC) valve is controlled by the Powertrain Control Module (PCM). PCM uses the IAC to maintain a desired idle speed, which varies depending on input to PCM. Scan tool reads IAC valve pintle position in counts. The higher the counts, the more air that is allowed to by-pass the throttle plate.

Conditions for setting this DTC are as follows

1. No VSS, TP sensor, EVAP system, EVAP solenoid, misfire, IAT sensor, MAP sensor, fuel trim, fuel injector, EGR pintle position, ECT sensor, CKP sensor, or MAF sensor related DTCs set.
2. BARO greater than 65 kPa.
3. System voltage 9-16 volts.
4. ECT greater than 122°F (70°C).
5. Engine running for at least 125 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. If any other DTCs are set, diagnose DTCs as necessary. If no other DTCs are set, go to next step.
3. Start engine. Ensure all accessories are off. Using scan tool, command RPM up to 1500, down to 650 and then up to 1500 while monitoring ENGINE SPEED display. If engine speed remains within 50 RPM of desired RPM for each RPM command, no problem is detected at this time. See DIAGNOSTIC AIDS. If engine speed does not remain within 50 RPM of desired RPM for each RPM command, go to next step.
4. Disconnect IAC valve harness connector. Install IAC Node Light (J 37027-A) to IAC valve harness connector. Using scan tool, command RPM up to 1500, down to 650 and then up to 1500 while monitoring ENGINE SPEED display. If each node light cycles Red and Green but never off, go to step 6). If each node light does not cycle Red and Green, go to next step.
5. Check for an open, short to voltage or short to ground in IAC valve related circuits between IAC valve and PCM. Repair as necessary. After repair is completed, go to step 11). If circuits are okay, go to step 9).
6. Check for vacuum leaks. Check for binding throttle plate or throttle shaft. Check for misadjusted throttle and cruise control cables. Check PCV system operation. Repair as necessary. After repairs, go to step 11). If no problem is found, go to next step.
7. Check for poor connection at IAC valve connector. Repair as necessary. After repairs, go to step 11). If no problem is found, go to next step.
8. Replace IAC valve. Repair as necessary. After repairs, go to step 11). If no problem is found, go to next step.
9. Check for poor connection at PCM valve connector. Repair as necessary. After repairs, go to step 11). If no problem is found, go to next step.
10. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
11. Start engine. Ensure all accessories are off. Using scan tool, command RPM up to 1500, down to 650 and then up to 1500 while monitoring ENGINE SPEED display. If engine speed remains within 50 RPM of desired RPM for each RPM command, repair is complete. See DIAGNOSTIC AIDS. If engine speed does not remain within 50 RPM of desired RPM for each RPM command, repeat step 2).

Inspect IAC valve connector for proper connection. Inspect throttle linkage for signs of binding or excessive wear. A slow or unstable idle may be caused by one of the following

1. Fuel system too rich or too lean.
2. Foreign material in throttle body bore or in air induction system.
3. Leaking or restricted intake manifold.
4. Excessive engine overloading.
5. Too high a viscosity engine oil.

Reviewing FAIL RECORDS vehicle mileage since diagnostic test last failed may help determine how often condition that caused DTC to be set occurs.

DTC P0530 - A/C REFRIGERANT PRESSURE SENSOR CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

PCM uses input signal from A/C refrigerant pressure sensor to determine if it should turn on engine coolant fans. When signal is out of range, DTC P0530 sets and PCM will not allow A/C clutch to engage.

Conditions required to set DTC are

1. Engine is running.
2. System voltage is greater than 10 volts.
3. A/C is requested.
4. A/C refrigerant pressure sensor signal less than 0.4 volt.

Or

1. A/C refrigerant pressure sensor signal greater than 4.6 volts.
2. Either condition present longer than 20 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Using scan tool, read A/C refrigerant pressure sensor voltage. If voltage is less than 0.1 volt, go to step 5). If voltage is not less than 0.1 volt, go to next step.
3. If voltage is greater than 4.8 volts, go to next step. If voltage is not greater than 4.6 volts, see DIAGNOSTIC AIDS.
4. While observing scan tool, disconnect A/C refrigerant pressure sensor connector. If voltage is about zero volts, go to step 12). If voltage is not as specified, go to step 11).
5. Disconnect A/C refrigerant pressure sensor connector. Connect a fused jumper wire between A/C refrigerant pressure sensor harness connector 5-volt reference and signal circuit. If voltage is about 5 volts, go to step 16). If voltage is not as specified, go to next step.
6. Using a DVOM, check voltage between A/C pressure sensor harness connector 5-volt reference and ground circuits. If voltage is about 5 volts, go to step 9). If voltage is not as specified, go to next step.
7. Check for faulty 5-volt reference circuit connection at PCM. If faulty connection is found, go to step 17). If connection is okay, go to next step.
8. Check for open or a faulty splice in 5-volt reference circuit. If problem is found, go to step 18). If no problem is found, go to step 13).
9. Check A/C refrigerant signal circuit for faulty connection at PCM. If faulty connection is found, go to step 17). If connection is okay, go to next step.
10. Check A/C refrigerant pressure signal circuit between A/C refrigerant pressure sensor connector and PCM for open or short to ground. If problem is found, go to step 18). If no problem is found, go to step 20).
11. Check A/C refrigerant pressure signal circuit between A/C refrigerant pressure sensor connector and PCM for short to voltage. If problem is found, go to step 18). If no problem is found, go to step 20).
12. Check 5-volt reference circuit for short to voltage. If problem is found, repair as necessary. After repairs, go to step 21). If no problem is found, go to next step.
13. Check for faulty sensor ground circuit terminal connection at PCM. If faulty connection is found, go to step 17). If connection is okay, go to next step.
14. Check for faulty sensor ground circuit terminal connection at A/C refrigerant pressure sensor connector. If faulty connection is found, go to step 17). If connection is okay, go to next step.
15. Check for open or faulty splice in sensor ground circuit. If a problem is found, go to step 18). If no problem is found, go to step 19).
16. Check for faulty 5-volt reference or A/C refrigerant pressure signal circuit terminal connection at A/C refrigerant pressure sensor. If faulty connection is found, go to next step. If connections are okay, go to step 19).
17. Replace faulty harness connector terminal. After repairs, go to step 21).
18. Locate and repair open/short circuit in wiring harness as necessary. After repairs, go to step 21).
19. Replace A/C refrigerant pressure sensor. After replacing sensor, go to step 21).
20. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
21. Using scan tool, clear DTCs. Read A/C refrigerant pressure sensor voltage. If voltage is 0.4-4.6 volts, repair is complete. If voltage is not as specified, return to step 2).

Check for faulty connections or damaged harness. Observe A/C PRESSURE display on scan tool while moving all related harness and connectors. A change in scan tool display indicates fault location.

DTC P0560 - SYSTEM VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

PCM monitors system voltage on PCM ignition feed circuit. If system voltage is out of range, DTC P0560 will set.

Conditions required to set DTC are

1. Engine is running.
2. System voltage monitored at PCM ignition feed circuit is less than 9 or greater than 16 volts.
3. Conditions present for longer than 25 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. If DTC P1635 is also set, diagnose DTC P1635 before proceeding. If DTC is not set, go to next step.
3. Start and run engine at greater than 1000 RPM. Using scan tool, observe IGNITION 1 voltage on ENG. 2 DATA LIST. If voltage is 10-16 volts, go to next step. If voltage is not as specified, go to step 5).
4. Read and record FAIL RECORDS data for DTC P0560. Clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC while operating vehicle. Continue operating vehicle until DTC P0560 test runs. If scan tool displays DTC P0560 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0560 FAILED THIS IGN, see DIAGNOSTIC AIDS.
5. Install DVOM between battery terminals. Monitor DVOM while running engine at greater than 1000 RPM. If voltage is 10-16 volts, go to next step. If voltage is not as specified, go to step 7).
6. Turn headlights on and place A/C switch on high. Monitor DVOM while running engine at greater than 2000 RPM. If voltage is 10-16 volts, go to step 8). If voltage is not as specified, go to next step.
7. Turn ignition off. Disconnect generator electrical connector. Turn ignition on. Connect DVOM between generator harness connector control circuit and engine ground. Using scan tool, command GEN L TERM on. If voltage is 10-16 volts, go to step 12). If voltage is not as specified, go to step 10).
8. Compare IGNITION 1 voltage display on scan tool with DVOM voltage reading. If both values are close, see DIAGNOSTIC AIDS. If both values are not close, go to next step.
9. Check PCM ignition feed circuit for poor connection between ignition switch and PCM. If problem is found, repair as necessary. After repairs, go to step 14). If no problem is found, go to step 13).
10. Check generator control circuit for open or short to ground between generator and PCM. If problem is found, repair as necessary. After repairs, go to step 14). If no problem is found, go to next step.
11. Check generator control circuit for faulty connection at PCM. If problem is found, repair as necessary. After repairs, go to step 14). If no problem is found, go to step 13).
12. Check generator control circuit for faulty connection at generator. If problem is found, repair as necessary. After repairs, go to step 14). If no problem is found, see DIAGNOSTIC AIDS.
13. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
14. Clear DTCs. Start and run engine at greater than 1000 RPM. Using scan tool, observe IGNITION 1 voltage on ENG. 2 DATA LIST. If voltage is 10-16 volts, repair is complete. If voltage is not as specified, return to step 2).

Check for faulty connections or damaged harness. Observe IGNITION 1 display on scan tool while moving all related harness and connectors. A change in scan tool display indicates fault location.

PCM uses an Electrically Erasable Programmable Read Only Memory (EEPROM). EEPROM contains program information and calibrations required for engine, transaxle, and powertrain diagnostics operation.

Condition required to set DTC is

1. PCM detects an internal program fault (check sum error).

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, repeat OBD system check.

Only possible repair is replacement and programming of PCM.

PCM uses an Electrically Erasable Programmable Read Only Memory (EEPROM). EEPROM contains program information and calibrations required for engine, transaxle, and powertrain diagnostics operation.

Condition required to set DTC

1. PCM does not contain correct program(s) required to operate vehicle.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Using special equipment, program PCM with correct software. Using scan tool, retest for DTC P0602. If DTC P0602 sets, go to next step. If DTC does not set, system is okay.
3. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, repeat OBD system check.

DTC P0705 - TRANSAXLE RANGE SWITCH CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Transaxle range switch is a multi-signal switch that sends a signal indicating gear selection to Powertrain Control Module (PCM). Transaxle range switch uses 4 circuits to pull PCM voltage low in various combinations to indicate each gear range. Voltage level of circuits is represented as "X (high voltage) or "O" (low voltage).

Conditions for setting DTC

1. PCM recognizes an invalid PRNDL parameter.
2. Vehicle speed greater than 5 MPH.

Transaxle Range Switch Valid Input Combination Values. Scheme 2

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check), then go to next step.
2. Turn ignition on, with engine off. Place transaxle gear selector in Park. Using scan tool, observe TRANS RANGE PABC display. Compare scan tool values with transaxle range switch valid input combination values. (Scheme 2) In Park, if all values are as specified, go to next step. If any value is not as specified, go to step 4).
3. Observe TRANS RANGE PABC display and move gear selector through all gear selections. Compare scan tool values with transaxle range switch valid input combination values. If all values are as specified, see DIAGNOSTIC AIDS. If any value is not as specified, go to step 10).
4. If all TRANS RANGE PABC values are indicated as "X" (high voltage), go to next step. If all values are not indicated as "X", go to step 7).
5. Check if transaxle range switch is disconnected. Repair as necessary. After repairs, go to step 17). If switch is not disconnected, go to next step.
6. Check transaxle range switch ground circuit for an open or poor connection. Repair as necessary. After repairs, go to step 17). If circuit is okay, go to step 13).
7. If all TRANS RANGE PABC values are indicated as "O" (low voltage), go to next step. If all values are not indicated as "O", go to step 10).
8. Disconnect transaxle range switch connector. Observe TRANS RANGE PABC display. If all TRANS RANGE PABC values are indicated as "O" (low voltage), go to next step. If all values are not indicated as "O", go to step 14).
9. Turn ignition off. Disconnect PCM connector. Check transaxle range switch wiring for pinched wires or short to ground. Repair as necessary. After repairs, go to step 17). If wiring is okay, go to step 16).
10. Check for crossed wires in transaxle range switch connector. Repair as necessary. After repairs, go to step 17). If connector is wired properly, go to next step.
11. Turn ignition off. Disconnect transaxle range switch and PCM connectors. Turn ignition on. Check for an open, short to ground or short to voltage in circuit that caused incorrect value reading in step 3). Repair as necessary. After repairs, go to step 17). If no problem is found, go to next step.
12. Reconnect transaxle range switch connector. Connect a test light between positive battery terminal and circuit terminal that caused incorrect value reading in step 3). Observe and note state of test light while moving gear selector through all gears. Compare test light state in each gear selection with transaxle range switch valid input combination values. If test light is on when value should be "O" and off when value should be "X", go to step 15). If test light is not as specified, go to next step.
13. Check for poor terminal connections at transaxle range switch connectors. Repair as necessary. After repairs, go to step 17). If terminal connections are okay, go to next step.
14. Replace defective transaxle range switch. After repairs, go to step 17).
15. Disconnect and inspect PCM connector for damaged pins, corrosion and loose wires. After repairs, go to step 17). If terminal connections are okay, go to next step.
16. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
17. Observe TRANS RANGE PABC display and move gear selector through all gear selections. Compare scan tool values with transaxle range switch valid input combination values. If all values are as specified, repair is complete. If any value is not as specified, repeat step 2).

Disconnect and inspect PCM connector. Inspect for damaged pins, corrosion and loose wires. An intermittent problem can be caused by a poor connection, rubbed-through wire insulation or broken wire inside insulation. Reviewing FAIL RECORDS vehicle mileage since diagnostic test last failed may help determine how often condition that caused DTC to be set occurs.

DTC P0706 - TRANSAXLE RANGE SWITCH PERFORMANCE

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Transaxle Range Switch (TRS) is part of Park/Neutral Position (PNP) switch. Inputs from TRS indicate to PCM which position is selected by gear selector lever. PCM uses this information for ignition timing, EVAP canister purge, EGR and IAC valve operation.

Combination of 4 TRS input states determine PCM commanded shift pattern. Input voltage level at PCM is high when TRS is open, and low when TRS is closed. If PCM detects engine start-up in any gear other than Park or Neutral, DTC P0706 is set.

Conditions for setting DTC

1. System voltage is greater than 9 volts.
2. TRS inputs indicate a gear position other than Park or Neutral during start-up.
3. Conditions present for longer than 5 consecutive start-ups.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. If DTC P0705 is also set, diagnose DTC P0705 before proceeding. If DTC is not set, go to next step.
3. Turn ignition on. Place gear selector in Park. Using scan tool, read TRANS RANGE display. If scan tool displays P-N, go to next step. If scan tool does not display P-N, go to step 5).
4. Place gear selector in Neutral. Read scan tool TRANS RANGE display. If scan tool displays P-N, see DIAGNOSTIC AIDS. If scan tool does not display P-N, go to next step.
5. Read scan tool TR PABC display. If scan tool displays P=O A=O B=O C=O, go to next step. If display is not as specified, go to step 10).
6. Disconnect TRS 4-pin harness connector. If scan tool displays P=O A=O B=O C=O, go to next step. If display is not as specified, go to step 8).
7. Turn ignition off. Disconnect PCM. Check TRS input circuit for being pinched or shorted to ground. If a problem is found, repair as necessary. After repairs, go to step 12). If no problem is found, go to step 11).
8. Attempt to adjust PNP/TRS switch. Read scan tool TRANS RANGE display with Park and Neutral selected. If scan tool displays P-N, go to step 12). If scan tool does not display P-N, go to next step.
9. Ensure wires in TRS 4-pin harness connector are not crossed. If a problem is found, repair as necessary. After repairs, go to step 12). If no problem is found, go to next step.
10. Replace TRS. After replacing switch, go to step 12).
11. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
12. Clear DTCs. Observe scan tool display while placing gear selector in each gear position. Record TR PABC status for each gear position. Compare scan tool display for each gear position with TRANSAXLE RANGE SWITCH VALID INPUT COMBINATIONS table. If scan tool display matches table entries for each gear selected, repair is complete. If scan tool display does not match table entries, return to step 3).

TRANSAXLE RANGE SWITCH VALID INPUT COMBINATIONS

Adjust PNP switch.

DTC P1106 - MAP SENSOR CIRCUIT INTERMITTENT HIGH VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Manifold Absolute Pressure (MAP) sensor measures changes in intake manifold pressure (vacuum). A low voltage signal, 2 volts, is sent to PCM on 5-volt reference circuit at closed throttle (high vacuum). A high voltage signal, 4 volts is sent at wide open throttle (low vacuum).

Conditions for setting DTC

1. No TP sensor DTCs set.
2. Engine has been running for predetermined time determined by start-up ECT.
3. TP angle less than 2 percent.
4. Engine speed less than 900 RPM.
5. MAP sensor intermittently indicates MAP voltage greater than 4.2 volts.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Using scan tool, select LAST TST FAIL. Record any other failed DTCs. If DTC P0108 is also set, diagnose DTC P0108 before proceeding. If DTC is not set, go to next step.
3. If DTC P1111, P1115, and/or P1121 is also set, go to step 6). If none of these DTCs are set, go to next step.
4. Check for faulty sensor ground circuit terminal at MAP sensor. If problem is found, go to step 9). If no problem is found, go to next step.
5. Check MAP signal circuit between MAP sensor harness connector and PCM for intermittent short to voltage. If a problem is found, go to step 10). If no problem is found, go to step 8).
6. Check for intermittent short to voltage on 5-volt reference circuit between PCM and MAP, EGR and TP sensors. If a problem is found, go to step 10). If no problem is found, go to next step.
7. Check for faulty ground circuit terminal connection at PCM. If problem is found, go to step 9). If no problem is found, go to next step.
8. Check for intermittent open or faulty splice in sensor ground circuit. If a problem is found, go to step 10). If no problem is found, go to DIAGNOSTIC AIDS.
9. Replace faulty connector terminal. After repairs, go to step 11).
10. Locate and repair intermittent open/short circuit. After repairs, go to next step.
11. Read and record FAIL RECORDS data for DTC P1106. Clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays that this DTC FAILED THIS IGN, return to step 2). If scan tool does not display that this DTC FAILED THIS IGN, repair is complete.

Check for faulty connections or damaged harness. Observe MAP display on scan tool while moving all related harnesses and connectors. A change in scan tool display indicates fault location.

DTC P1107 - MAP SENSOR CIRCUIT INTERMITTENT LOW VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Manifold Absolute Pressure (MAP) sensor measures changes in intake manifold pressure (vacuum). A low voltage signal, 2 volts, is sent to PCM on 5-volt reference circuit at closed throttle (high vacuum). A high voltage signal, 4 volts is sent at wide open throttle (low vacuum).

Conditions required to set DTC are

1. No TP sensor DTCs set.
2. Engine is running.
3. TP angle greater than zero percent with engine speed less than 1000 RPM.
4. TP angle greater than 5 percent with engine speed greater than 1000 RPM.
5. MAP sensor intermittently indicating MAP voltage less than 0.1 volt.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Using scan tool, select LAST TST FAIL. Record any other failed DTCs. If DTC P0107 is also set, diagnose DTC P0107 before proceeding. If DTC is not set, go to next step.
3. If DTC P1122 is also set, go to step 6). If DTC is not set, go to next step.
4. Check for faulty 5-volt reference or signal circuit connection at MAP sensor. Repair as necessary. After repairs, go to step 9). If circuit or connection is okay, go to next step.
5. Check signal circuit between MAP sensor and PCM connector for intermittent open or short to ground. Repair as necessary. After repairs are complete, go to step 10). If circuit is okay, go to step 8).
6. Check for intermittent short to ground on 5-volt reference circuit between PCM and EGR valve, MAP and TP sensors. Repair as necessary. After repairs, go to step 10). If circuit is okay, go to next step.
7. Check for faulty 5-volt reference circuit connection at PCM. If faulty connection is found, go to step 9). If connection is okay, go to next step.
8. Check for intermittent open or faulty splice in 5-volt reference circuit. Repair as necessary. After repairs, go to step 10). If circuit is okay, go to DIAGNOSTIC AIDS.
9. Replace faulty connector terminal(s). After replacing terminals, go to step 11).
10. Repair circuit as necessary. After repairs, go to next step.
11. Using scan tool, read and record FAIL RECORDS DATA, and clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, select SPECIFIC DTC INFO for DTC P1107. If scan tool displays DTC P1107 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P1107 FAILED THIS IGN, repair is complete.

Check for faulty connections or damaged harness. Observe MAP display on scan tool MAP while moving all related harnesses and connectors. A change in scan tool display indicates fault location.

DTC P1111 - IAT SENSOR CIRCUIT INTERMITTENT HIGH VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Intake Air Temperature (IAT) sensor is a thermistor. PCM applies and reads a 5-volt reference signal to sensor. When air is cold, sensor resistance is high and PCM will measure a high signal voltage. If air is warm, sensor resistance is low causing PCM to measure low voltage.

Conditions required to set DTC are

1. Vehicle speed less than 35 MPH.
2. IAT signal voltage intermittently indicates IAT less than -38°F (-39°C).
3. Conditions present up to 3 minutes.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Using scan tool, select LAST TST FAIL. Record any other failed DTCs. If DTC P0113 is also set, diagnose DTC P0113 before proceeding. If DTC is not set, go to next step.
3. If DTC P1106, P1115, and/or P1121 is also set, go to step 6). If none of these DTCs are set, go to next step.
4. Check for faulty sensor ground circuit terminal at IAT sensor. Repair as necessary. After repairs, go to step 10). If circuit is okay, go to next step.
5. Check for faulty signal circuit connection at IAT sensor. Repair as necessary. After repairs, go to step 10). If connection is okay, go to next step.
6. Check IAT signal circuit between IAT sensor connector and PCM for intermittent open. Repair as necessary. After repairs, go to step 10). If circuit is okay, go to next step.
7. Check IAT signal circuit between IAT sensor harness connector and PCM for intermittent short to voltage. Repair as necessary. After repairs, go to step 10). If circuit is okay, go to next step.
8. Check for faulty ground circuit terminal connection at PCM. Repair as necessary. After repairs, go to step 10). If connection is okay, go to next step.
9. Check for intermittent open or faulty splice in sensor ground circuit. Repair as necessary. After repairs, go to next step. If no problem is found, see DIAGNOSTIC AIDS.
10. Read and record FAIL RECORDS data for DTC P1111. Clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P1111 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P1111 FAILED THIS IGN, repair is complete.

Check for faulty connections or damaged harness. Observe IAT display on scan tool while moving all related harnesses and connectors. A change in scan tool display indicates fault location. Check for skewed IAT sensor. See IAT TEMPERATURE-TO-RESISTANCE VALUES table.

DTC P1112 - IAT SENSOR CIRCUIT INTERMITTENT LOW VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Intake Air Temperature (IAT) sensor is a thermistor. PCM applies and reads a 5-volt reference signal to sensor. When air is cold, sensor resistance is high and PCM will measure a high signal voltage. If air is warm, sensor resistance is low causing PCM to measure low voltage.

Conditions for setting DTC

1. Vehicle speed greater than 25 MPH.
2. IAT sensor voltage intermittently less than 0.14 volt.
3. Conditions present for up to 30 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Using scan tool, select LAST TST FAIL. Record any other failed DTCs. If DTC P0112 is also set, diagnose DTC P0112 before proceeding. If DTC is not set, go to next step.
3. Check IAT signal circuit between IAT sensor harness connector and PCM for intermittent short to ground. Repair as necessary. After repairs, go to next step. If circuit is okay, see DIAGNOSTIC AIDS.
4. Read and record FAIL RECORDS data for DTC P1112. Clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P1112 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P1112 FAILED THIS IGN, repair is complete.

Check for faulty connections or damaged harness. Observe IAT display on scan tool while moving all related harnesses and connectors. A change in scan tool display indicates fault location. Check for skewed IAT sensor. See IAT TEMPERATURE-TO-RESISTANCE VALUES table.

DTC P1114 - ECT SENSOR CIRCUIT INTERMITTENT LOW VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Engine Coolant Temperature (ECT) sensor is a thermistor that varies resistance based on temperature. As temperature of sensor increases, resistance decreases. High temperature will result in a low signal voltage. DTC will set when PCM sees an ECT sensor voltage intermittently less than 1.5 volt.

Conditions for setting DTC

1. Engine running.
2. ECT sensor signal voltage intermittently less than .14 volt.
3. Conditions present for greater than 15 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Using scan tool, select LAST TST FAIL. Record any other failed DTCs. If DTC P0117 is also set, diagnose DTC P0117 before proceeding. If DTC is not set, go to next step.
3. Check ECT signal circuit between ECT sensor harness connector and PCM for intermittent short to ground. Repair as necessary. After repairs, go to next step. If circuit is okay, see DIAGNOSTIC AIDS.
4. Read and record FAIL RECORDS data for DTC P1114. Clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P1114 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P1114 FAILED THIS IGN, repair is complete.

Check for faulty connections or damaged harness. Observe ECT display on scan tool while moving all related harnesses and connectors. A change in scan tool display indicates fault location. Check for skewed ECT sensor. See ECT TEMPERATURE-TO-RESISTANCE VALUES table.

DTC P1115 - ECT SENSOR CIRCUIT INTERMITTENT HIGH VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Engine Coolant Temperature (ECT) sensor is a thermistor or a variable resistor, that varies resistance based on temperature. As temperature of sensor increases, resistance decreases. High temperature will result in a low signal voltage. DTC will set when PCM sees an ECT sensor voltage intermittently greater than 2 volts.

Conditions for setting DTC

1. Engine running.
2. ECT sensor signal voltage is intermittently greater than 4.8 volts.
3. Conditions present for greater than 3 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Using scan tool, select LAST TST FAIL. Record any other failed DTCs. If DTC P0118 is also set, diagnose DTC P0118 before proceeding. If DTC is not set, go to next step.
3. If DTC P1106, P1111, and/or P1121 is also set, go to step 8). If none of these DTCs are set, go to next step.
4. Check for faulty sensor ground circuit terminal at ECT sensor. Repair as necessary. After repairs, go to step 10). If circuit is okay, go to next step.
5. Check for faulty signal circuit connection at ECT sensor. Repair as necessary. After repairs, go to step 10). If connection is okay, go to next step.
6. Check ECT signal circuit between ECT sensor harness connector and PCM for intermittent open. Repair as necessary. After repairs are complete, go to step 10). If circuit is okay, go to next step.
7. Check ECT signal circuit between ECT sensor harness connector and PCM for intermittent short to voltage. Repair as necessary. After repairs, go to step 10). If circuit is okay, go to next step.
8. Check for faulty ground circuit terminal connection at PCM. Repair as necessary. After repairs, go to step 10). If connection is okay, go to next step.
9. Check for intermittent open or faulty splice in sensor ground circuit. Repair as necessary. After repairs, go to next step. If circuit is okay, see DIAGNOSTIC AIDS.
10. Read and record FAIL RECORDS data for DTC P1115. Clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P1115 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P1115 FAILED THIS IGN, repair is complete.

Check for faulty connections or damaged harness. Observe ECT display on scan tool while moving all related harnesses and connectors. A change in scan tool display indicates fault location. Check for skewed ECT sensor. See ECT TEMPERATURE-TO-RESISTANCE VALUES table.

DTC P1121 - TP SENSOR CIRCUIT INTERMITTENT HIGH VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Throttle Position (TP) sensor measures amount of throttle opening. PCM uses TP sensor information for fuel delivery calculations. TP sensor readings during acceleration are much higher than those during deceleration or idle. DTC P1121 sets if PCM senses TP sensor voltage intermittently greater than 4.7 volts.

Conditions for setting DTC

1. Engine running.
2. TP signal voltage is intermittently greater than 4.7 volts.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Using scan tool, select LAST TST FAIL. Record any other failed DTCs. If DTC P0123 is also set, diagnose DTC P0123 before proceeding. If DTC is not set, go to next step.
3. If DTC P1106, P1111, and/or P1115 is also set, go to step 6). If none of these DTCs are set, go to next step.
4. Check for faulty sensor ground circuit terminal at TP sensor. Repair as necessary. After repairs, go to step 9). If circuit is okay, go to next step.
5. Check TP signal circuit between TP sensor harness connector and PCM for intermittent short to voltage. Repair as necessary. After repairs, go to step 10). If circuit is okay, go to step 8).
6. Check for intermittent short to voltage on 5-volt reference circuit between PCM and MAP, EGR and TP sensors. Repair as necessary. After repairs, go to step 10). If circuit is okay, go to next step.
7. Check for faulty ground circuit terminal connection at PCM. Repair as necessary. After repairs, go to step 9). If connection is okay, go to next step.
8. Check for intermittent open or faulty splice in sensor ground circuit. Repair as necessary. After repairs, go to step 10). If circuit is okay, see DIAGNOSTIC AIDS.
9. Replace faulty connector terminal. After replacing terminals, go to step 11).
10. Locate and repair intermittent open/short circuit. After repairs, go to next step.
11. Read and record FAIL RECORDS data for DTC P1121. Clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P1121 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P1121 FAILED THIS IGN, repair is complete.

Check for faulty connections or damaged harness. Observe TP SENSOR display on scan tool while moving all related harnesses and connectors. A change in scan tool display indicates fault location.

DTC P1122 - TP SENSOR CIRCUIT INTERMITTENT LOW VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Throttle Position (TP) sensor measures amount of throttle opening. PCM uses TP sensor information for fuel delivery calculations. TP sensor readings during acceleration are much higher than those during deceleration or idle. DTC P1121 sets if PCM senses TP sensor voltage intermittently less than 0.16 volt.

Conditions required to set DTC are

1. Engine running.
2. TP signal voltage is intermittently less than 0.16 volt.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Using scan tool, select LAST TST FAIL. Record any other failed DTCs. If DTC P0122 is also set, diagnose DTC P0122 before proceeding. If DTC is not set, go to next step.
3. If DTC P1107 is also set, go to step 6). If DTC is not set, go to next step.
4. Check for faulty 5-volt reference or signal circuit connection at TP sensor. Repair as necessary. After repairs, go to step 9). If circuit is okay, go to next step.
5. Check signal circuit between TP sensor and PCM for intermittent open or short to ground. Repair as necessary. After repairs, go to step 10). If circuit is okay, go to step 8).
6. Check for intermittent short to ground on 5-volt reference circuit between PCM and EGR valve, MAP and TP sensors. Repair as necessary. After repairs, go to step 10). If circuit is okay, go to next step.
7. Check for faulty 5-volt reference circuit connection at PCM. Repair as necessary. After repairs, go to step 9). If connection is okay, go to next step.
8. Check for intermittent open or faulty splice in 5-volt reference circuit. Repair as necessary. After repairs, go to step 10). If circuit is okay, see DIAGNOSTIC AIDS.
9. Replace faulty connector terminal(s). After repairs, go to step 11).
10. Repair circuit as necessary. After repairs, go to next step.
11. Using scan tool, read and record FAIL RECORDS DATA, and clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, select SPECIFIC DTC INFO for DTC P1122. If scan tool displays DTC P1122 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P1122 FAILED THIS IGN, repair is complete.

Check for faulty connections or damaged harness. Observe TP SENSOR display on scan tool while moving all related harnesses and connectors. A change in scan tool display indicates fault location.

DTC P1133 - HO2S INSUFFICIENT SWITCHING SENSOR 1

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

PCM monitors Heated Oxygen Sensor (HO2S) activity for 100 seconds. PCM determines if HO2S 1 is functioning properly by counting number of HO2S 1 Lean/Rich (L/R) and Rich/Lean (R/L) switches. If PCM determines that HO2S 1 did not switch enough times, DTC 1133 is set.

Conditions for setting DTC

1. No CKP, ECT, EGR pintle position, IAT, MAF, MAP, or TP sensor DTCs set.
2. No fuel trim, injector or HO2S 1 heater circuit DTCs set.
3. No EVAP system DTCs set.
4. Conditions present during 100 second monitoring period.
5. HO2S 1 L/R and R/L switches less than 45.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Using scan tool, select LAST TST FAIL. Record any other failed DTCs. If any DTC other than P1133 or P1134 sets, diagnose affected DTC before proceeding. If no other DTC sets, start engine and allow it to idle. Operate vehicle within conditions required to set DTC. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P1133 FAILED THIS IGN, go to next step. If scan tool does not display DTC P1133 FAILED THIS IGN, go to DIAGNOSTIC AIDS.
3. Check exhaust system for leaks. If exhaust leak is found, repair as necessary. After repairs, go to step 11). If no exhaust leak is found, go to next step.
4. Visually inspect HO2S 1 for secure installation or corrosion on terminals. Check terminal tension at HO2S 1 and PCM. Check for damaged wiring. If a problem is found, go to step 8). If no problem is found, go to next step.
5. Disconnect HO2S 1 harness connector. Connect a jumper wire between HO2S 1 harness connector ground circuit and chassis ground. Using scan tool, read HO2S 1 voltage. If voltage is about 0.45 volt, go to next step. If voltage is not as specified, go to step 9).
6. Connect a jumper wire between HO2S 1 harness connector signal and ground circuits, and chassis ground. If voltage is less than 0.3 volt, go to next step. If voltage is not less than 0.3 volt, go to step 10).
7. Repair condition causing fuel, sealant, oil or coolant contamination. Replace affected HO2S. After replacing sensor, go to step 11).
8. Repair condition as necessary. After repairs, go to step 11).
9. Repair open HO2S 1 ground circuit or HO2S 1 signal circuit shorted to ground. After repairs, go to step 11).
10. Repair open HO2S 1 signal circuit or faulty PCM connections as necessary. After repairs, go to next step.
11. Using scan tool, read and record FAIL RECORDS DATA, and clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, select SPECIFIC DTC INFO for DTC P1133. If scan tool displays DTC P1133 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P1133 FAILED THIS IGN, repair is complete.

Check HO2S 1 heater circuits for intermittent faults. If HO2S 1 heater circuits are okay, replace HO2S 1.

DTC P1134 - HO2S TRANSITION TIME RATIO SENSOR 1

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

PCM reads Heated Oxygen Sensor (HO2S) activity for 100 seconds. During this period, PCM counts the number of Lean/Rich (L/R) and Rich/Lean (R/L) switches.

With this information, an average time for all transitions can be determined. PCM then divides R/L average by L/R rich average to obtain a ratio. If HO2S ratio is not within range, DTC P1134 will set.

Conditions for setting DTC

1. No ECT, IAT, MAF, MAP, or TP sensor DTCs set.
2. No fuel trim, injector or HO2S 1 heater circuit DTCs set.
3. No EGR or EVAP system DTCs set.
4. Engine speed 1000-3000 RPM.
5. Engine operating in closed loop mode.
6. Conditions present during 100 second monitoring period.
7. Ratio of average response times not 0.4-5.0.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Using scan tool, select LAST TST FAIL. Record any other failed DTCs. If any DTC other than P1133 or P1134 sets, diagnose affected DTC before proceeding. If no other DTC sets, start engine and allow it to idle. Operate vehicle within conditions required to set DTC. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P1134 FAILED THIS IGN, go to next step. If scan tool does not display DTC P1134 FAILED THIS IGN, go to DIAGNOSTIC AIDS.
3. Check exhaust system for leaks. If exhaust leak is found, repair as necessary. After repairs, go to step 11). If no exhaust leak is found, go to next step.
4. Visually inspect HO2S 1 for secure installation or corrosion on terminals. Check terminal tension at HO2S 1 and PCM. Check for damaged wiring. If a problem is found, go to step 8). If no problem is found, go to next step.
5. Disconnect HO2S 1 connector. Connect a jumper wire betweenHO2S 1 harness connector ground circuit and chassis ground. Using scan tool, read HO2S 1 voltage. If voltage is about 0.45 volt, go to next step. If voltage is not as specified, go to step 9).
6. Connect a jumper wire between HO2S 1 harness connector signal and ground circuits, and chassis ground. If voltage is less than 0.3 volt, go to step 12). If voltage is not less than 0.3 volt, go to step 10).
7. Repair condition causing fuel, sealant, oil or coolant contamination. Replace affected HO2S and go to step 11).
8. Repair condition as necessary. After repairs, go to step 11).
9. Repair open HO2S 1 ground circuit or HO2S 1 signal circuit shorted to ground, go to step 11).
10. Repair open HO2S 1 signal circuit or faulty PCM connections. After repairs, go to next step.
11. Using scan tool, read and record FAIL RECORDS DATA, and clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, select SPECIFIC DTC INFO for DTC P1134. If scan tool displays DTC P1134 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P1134 FAILED THIS IGN, repair is complete.

Check HO2S 1 heater circuits for intermittent faults. If HO2S 1 heater circuits are okay, replace HO2S 1.

DTC P1336 - CKP SYSTEM VARIATION NOT LEARNED

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

The crankshaft position system variation learning feature is used to calculate reference period errors caused by slight tolerance variations in the crankshaft, the crankshaft balancer interrupter rings, and the crankshaft position sensor hall effect switches. The calculated error allows PCM to accurately compensate for reference period variations. The crankshaft position system variation learning feature enhances the ability of the PCM to detect misfire events over a wider range of engine speed and load.

The crankshaft position system variation values are stored in the PCM non-volatile memory after the crankshaft position system variation learn procedure has been performed. DTC P1336 set indicates that the crankshaft position system variation values have not been stored in the PCM and the crankshaft position system variation learn procedure must be performed. The learn procedure is required after the following service procedures have been performed, regardless of whether or not DTC P1336 is set

1. PCM replacement
2. Engine replacement
3. Crankshaft balancer replacement
4. Crankshaft position sensor replacement
5. Any engine repair(s) which disturbs crankshaft/harmonic balancer to crankshaft position sensor relationship.

Conditions for setting DTC

1. Crankshaft position system variation values are not stored in the PCM memory.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Perform crankshaft position system variation learn position.

The crankshaft position system variation compensating values are stored in the PCM's non-volatile memory after a learn procedure has been performed. If actual crankshaft position variation is not within the crankshaft position system variation compensating values stored in the PCM, DTC P0300 may set.

If the crankshaft position system variation learn procedure cannot be performed successfully, check the following conditions and correct as necessary

1. ECT less than 158°F (70°C).
2. Allow engine to warm-up to greater than 158°F (70°C).
3. PCM related DTC(s) set.
4. Scan tool crankshaft position system variation learn function will be disabled of any PCM DTCs other than DTC P1336 are stored.
5. Camshaft position signal problem detected.
6. 3X reference signal problem detected.
7. 24X reference signal problem detected.

DTC P1351 - IGNITION CONTROL (IC) CIRCUIT OPEN

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

The Ignition Control Module (ICM) sends signals that PCM requires for fuel control and spark advance calculations. At start of engine crank, ICM controls spark advance (by-pass mode). When the second 3X reference pulse is recognized by the PCM, PCM applies 5 volts to by-pass circuit, commanding ICM to switch spark advance to PCM control (IC mode). If PCM detects an open in the IC circuit, DTC will set. Engine will start and may run in by-pass mode timing.

Conditions for setting DTC

1. Engine running.
2. PCM detects an open in IC circuit.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Turn ignition off. Disconnect PCM harness connector. Check resistance between IC and reference low circuit. If resistance is less than 500 ohms, go to step 4). If resistance is not less 500 ohms, go to next step.
3. Disconnect ICM harness connector. Check for open in IC circuit. Repair as necessary. After repairs, go to step 8). If circuit is okay, go to step 5).
4. Check for poor terminal connections at PCM. Repair as necessary. After repairs, go to step 8). If connections are okay, go to step 7).
5. Check for poor terminal connections at ICM. Repair as necessary. After repairs, go to step 8). If connections are okay, go to next step.
6. Replace ICM. After replacing module, go to step 8).
7. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
8. Read and record FAIL RECORDS data for this DTC. Clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC FAILED THIS IGN, return to step 2). If scan tool does not display DTC FAILED THIS IGN, repair is complete.

Check for faulty connections or damaged harness. If connections and harness appear okay, observe scan tool while moving all related harnesses and connectors. A change in scan tool display indicates fault location.

DTC P1352 - BY-PASS LINE OPEN

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

The Ignition Control Module (ICM) sends signals that PCM requires for fuel control and spark advance calculations. At start of engine crank, ICM controls spark advance (by-pass mode). When the second 3X reference pulse is recognized by the PCM, PCM applies 5 volts to by-pass circuit, commanding ICM to switch spark advance to PCM control (IC mode). If PCM detects an open in the IC circuit, DTC will set. Engine will start and may run in by-pass mode timing.

Conditions for setting DTC

1. Engine running.
2. PCM detects an open in by-pass circuit.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Turn ignition off. Disconnect PCM harness connector. Turn ignition on. Connect DVOM between IC and reference low circuit. Connect test light between battery voltage and by-pass circuit. If resistance is greater than 5000 ohms, go to step 4). If resistance is not greater than 5000 ohms, go to next step.
3. Turn ignition off. Disconnect ICM harness connector. Check for open in by-pass circuit. Repair as necessary. After repairs, go to step 8). If circuit is okay, go to step 5).
4. Check for poor terminal connections at PCM. Repair as necessary. After repairs, go to step 8). If connections are okay, go to step 7).
5. Check for poor terminal connections at ICM. Repair as necessary. After repairs, go to step 8). If connections are okay, go to next step.
6. Replace ICM. After replacing module, go to step 8).
7. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
8. Read and record FAIL RECORDS data for this DTC. Clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC FAILED THIS IGN, return to step 2). If scan tool does not display DTC FAILED THIS IGN, repair is complete.

Check for faulty connections or damaged harness. If connections and harness appear okay, observe scan tool while moving all related harnesses and connectors. A change in scan tool display indicates fault location.

DTC P1361 - IGNITION CONTROL CIRCUIT NOT TOGGLING

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Ignition Control Module (ICM) sends signals that PCM requires for fuel control and spark advance calculations. At start of engine crank, ICM controls spark advance (by-pass mode). When second 3X signal is recognized by PCM, it applies 5 volts to by-pass circuit, commanding ICM to switch Ignition Control (IC) of spark advance to PCM (IC mode). A short in IC circuit, or an open or short ground in by-pass circuit will set DTC 1361.

Condition required to set DTC is

1. PCM senses IC pulses during crank while by-pass mode spark advance is commanded.
2. Engine speed greater than 600 RPM.
3. DTC P1350 not set.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Using scan tool, clear DTCs. Start engine and allow it to idle for 2 minutes. Read DTCs. If DTC P1361 sets, go to next step. If DTC does not set, see DIAGNOSTIC AIDS.
3. Turn ignition off. Disconnect PCM connectors. Turn ignition on. Connect a test light between battery voltage and PCM harness connector by-pass circuit. If test light illuminates, go to step 8). If test light does not illuminate, go to next step.
4. Turn ignition on. with test light still connected between battery voltage and PCM harness connector by-pass circuit, use a DVOM to check resistance between PCM harness connector IC circuit and reference low circuit. If resistance 6000 ohms or greater, go to step 9). If resistance is not 6000 ohms or greater, go to next step.
5. Turn ignition off. Disconnect ICM 14-pin connector. Check resistance between ICM 14-pin harness connector IC circuit and engine ground. If resistance is infinite, go to next step. If resistance is not infinite, go to step 10).
6. Check by-pass circuit for open. If open is found, repair as necessary. After repairs, go to step 15). If circuit is open, go to next step.
7. Check by-pass circuit for faulty connection at ICM. If faulty connection is found, repair as necessary. After repairs, go to step 15). If connection is okay, go to step 14).
8. Turn ignition off. Disconnect ICM 14-pin connector. Turn ignition on. If test light illuminates, go to step 11). If test light does not illuminate, go to step 14).
9. Turn ignition off. Disconnect ICM connectors. Turn ignition on. Check IC circuit for short to voltage. If short to voltage is found, repair as necessary. After repairs, go to step 15). If circuit is okay, go to step 13).
10. Locate and repair short to ground in IC circuit. After repairs, go to step 15).
11. Locate and repair short to ground in by-pass circuit. After repairs, go to step 15).
12. Check by-pass circuit for faulty connection at PCM. If faulty connection is found, repair as necessary. After repairs, go to step 15). If connection is okay, go to next step.
13. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to step 15).
14. Replace ICM. After replacing ICM, go to next step.
15. Read and record FAIL RECORDS data for this DTC. Clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC FAILED THIS IGN, return to step 2). If scan tool does not display DTC FAILED THIS IGN, repair is complete.

Check for faulty connections or damaged harness. Disconnect ICM. Connect a DVOM between ICM harness connector IC circuit and battery voltage. With ignition on, observe DVOM while moving all related harnesses and connectors. A change in voltage display indicates fault location.

DTC P1374 - 3X REFERENCE CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

3X reference circuit is produced by Ignition Control Module (ICM). PCM uses 3X reference signal pulses to calculate engine speed (RPM) and crankshaft position at engine speed more than 1200 RPM. PCM uses pulses on this circuit to initiate injector pulses. If PCM receives incorrect number of pulses on 3X reference circuit, DTC P1374 will set.

Conditions required to set DTC are

1. Engine running and PCM is receiving 24X reference signal pulses.
2. Ratio of 24X reference signal pulses to 3X reference signal pulses received by PCM do not equal 8.
3. Ratio of 24X reference signal pulses to camshaft reference signal pulses received by PCM equals 48.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Attempt to start engine. If engine starts and runs, go to next step. If engine does not start and run, see BASIC TESTING - 3.1L article.
3. Using scan tool, read and record FAILS RECORD DATA. Operate vehicle within conditions noted in FAILED RECORDS DATA. Read SPECIFIC DTC. If scan tool displays DTC P1374 FAILED THIS IGN, go to next step. If scan tool does not display DTC P1374 FAILED THIS IGN, go to DIAGNOSTIC AIDS.
4. Install Injector Test Light (J 34730-2A) to any injector harness connector. Turn ignition on. Using a test light connected to ground, repeatedly touch test light lead to 3X reference signal circuit while observing injector test light. If injector test light blinks/flashes, go to step 8). If injector test light does not flash, go to next step.
5. Turn ignition off. Disconnect PCM connector. Check 3X reference signal circuit for open or short to ground. If problem is found, go to step 11). If no problem is found, go to next step.
6. Check for faulty 3X reference signal circuit connection at PCM. If connection is faulty, repair as necessary. After repairs, go to step 11). If connection is okay, go to next step.
7. Check for incorrect harness routing near secondary ignition components, ignition coil arcing to wiring harness or ICM. Check ignition coils for cracks, carbon tracking or other signs of damage. Check for secondary ignition wire(s) arcing to wiring harness. If a problem is found, repair as necessary. After repairs, go to step 11). If no problem is found, go to step 10).
8. Check for faulty connections at ICM. If faulty connection is found, repair as necessary. After repairs, go to step 11). If connections are okay, go to next step.
9. Replace ICM. After replacing ICM, go to step 11).
10. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
11. Read and record FAIL RECORDS data for this DTC. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, read SPECIFIC DTC. If scan tool displays DTC P1374 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P1374 FAILED THIS IGN, repair is complete.

Check for faulty connections or damaged harness. Observe a voltmeter connected to 3X reference circuit at PCM harness connector while moving all related harnesses and connectors. A change in voltage indicates fault location.

Check for incorrect harness routing near secondary ignition components, ignition coil arcing to wiring harness or ICM. Check ignition coils for cracks, carbon tracking or other signs of damage. Check for secondary ignition wire(s) arcing to wiring harness.

DTC P1380 - EBCM DTC DETECTED ROUGH ROAD DATA UNUSABLE

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

PCM receives rough road information from EBCM/EBTCM on the serial data circuit. PCM uses this information to enhance the misfire diagnostic by distinguishing crankshaft speed variations caused by driving on rough road surfaces from variations caused by true misfires. EBCM/EBTCM transmits rough road information based on inputs from wheel speed sensors. If EBCM/EBTCM detects a condition which will allow it to properly identify rough road situations while a misfire condition is being detected by the PCM, DTC will set.

Conditions for setting DTC

1. Engine load less than 87 percent.
2. Engine speed less than 5000 RPM.
3. Vehicle speed greater than 10 MPH.
4. Misfire DTC is occurring and requesting MIL to be illuminated.
5. PCM has detected an EBCM/EBTCM rough road sensing error.

Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK , then diagnose ABS/TCS system. See ANTI-LOCK BRAKE SYSTEM article in BRAKES section.

If this DTC is set, it indicates that the ABS/TCS system has detected a malfunction which will not allow the EBCM/EBTCM to transmit correct rough data to PCM. Diagnose ABS system. See ANTI-LOCK BRAKE SYSTEM article in BRAKES section.

DTC P1381 - MISFIRE DETECTED NO EBCM/PCM SERIAL DATA

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

PCM receives rough road information from the EBCM/EBTCM on the Class II serial data circuit. PCM detects engine misfire by detecting variations in crankshaft deceleration between firing strokes. For accurate detection of engine misfire, PCM must be able to distinguish between crankshaft deceleration caused by actual misfire or deceleration caused by rough road conditions.

The ABS system can detect if vehicle is on a rough road based on wheel acceleration/deceleration data supplied by the wheel speed sensors. If ABS system detects rough road above a predetermined threshold, this information is sent to the PCM via the serial data (UART). PCM can then take the rough road into account when calculating misfire. Even if the ABS is malfunctioning and cannot detect rough roads, the misfire diagnostic will continue to run.

Conditions for setting this DTC are as follows

1. Engine load less than 87 percent.
2. Vehicle speed is greater than 10 MPH.
3. Engine speed is less than 5000 RPM.
4. A misfire DTC is occurring and requesting MIL to be illuminated.
5. PCM has detected a rough road data error for at least 5 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Turn ignition on, with engine off. Using scan tool, attempt to display ABS data. If ABS data can be displayed, go to next step. If ABS data cannot be displayed, go to step 4).
3. Check serial data circuit for an open or poor connection between PCM and EBCM. Repair as necessary. After repairs, go to step 7). If circuit is okay, see DIAGNOSTIC AIDS.
4. Turn ignition off. Disconnect EBCM. Turn ignition on. Using DVOM, measure voltage between ground and serial data circuit terminal at Electronic Brake Control Module (EBCM) connector. If voltage is 1-5 volts, go to next step. If measured voltage is not 1-5 volts, go to step 6).
5. Check for poor terminal connections at EBCM connector. Repair as necessary. After repairs, go to step 7). If connections are okay, go to next step.
6. Check for an open or short to ground in serial data circuit. Repair as necessary. After repair is completed, go to next step. If circuit is okay, check ABS system. See ANTI-LOCK BRAKE SYSTEM article in BRAKES section.
7. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for DTC P1381 until DTC P1381 test runs. If scan tool indicates FAILED THIS IGN, repeat step 2). If scan tool does not indicate FAILED THIS IGN, repair is complete.

Setting of this DTC indicates that a misfire was detected and that the PCM could not determine if fault was a true misfire or due to operating vehicle on a rough surface. A misfire can be a true misfire with or without setting this DTC. Check PCM or Electronic Brake Control Module (EBCM) for poor connections.

DTC P1404 - EGR VALVE PINTLE STUCK OPEN

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

PCM monitors EGR valve pintle position input to ensure that valve responds properly to commands from the PCM. When ignition is turned on, PCM learns the EGR closed valve pintle position. PCM compares the learned EGR closed valve pintle position to the actual position when EGR valve is commanded closed. If actual EGR position indicates that EGR valve is still open when PCM is commanding EGR closed, DTC will set.

Conditions for setting DTC

1. No CKP, ECT, IAT, MAF, MAP, TP or VSS DTC set.
2. No misfire, idle speed, fuel injector related DTCs set.
3. System voltage 10-16 volts.
4. EGR feedback is .2 volt greater than EGR closed valve pintle position when desired EGR position is commanded to zero percent.
5. Conditions present for longer than 20 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step. NOTE: If DTC P0403 is set, diagnose DTC P0403 first.
2. Start and operate engine at idle. Using scan tool, observe actual EGR position. If actual EGR position is zero percent, go to next step. If actual EGR position is not zero percent, go to step 5).
3. Turn ignition on, engine off. Using scan tool, select EGR VALVE OUTPUT CONTROL function. Increment EGR valve through all positions while comparing desired to actual EGR position. If desired EGR position remains close to actual EGR position at all commanded positions, go to next step. If desired EGR position does not remain close to actual EGR position, go to step 6).
4. Using scan tool, review and record FAIL RECORDS data. Operate vehicle within FAIL RECORDS conditions. Monitor SPECIFIC DTC INFO for this DTC until DTC P1404 test runs. If scan tool indicates that this DTC failed this ignition cycle, go to next step. If scan does not indicate that this DTC failed this ignition cycle, see DIAGNOSTIC AIDS.
5. Disconnect EGR harness connector. Observe actual EGR position on scan tool. If actual EGR position is at zero percent, go to next step. If actual EGR position is not at zero percent, go to step 7).
6. Using test light connected to battery voltage, probe test light to EGR pintle position sensor ground circuit. If test light illuminates, go to step 9). If test light does not illuminate, go to step 8).
7. Turn ignition off. Disconnect PCM harness connector. Turn ignition on, engine off. Check voltage between ground and EGR pintle position signal circuit. If voltage reading is zero volts, go to step 12). If voltage reading is not zero volts, go to step 11).
8. Check EGR pintle position sensor ground circuit for an open between EGR and EGR valve. Repair as necessary. After repairs, go to step 15). If circuit is okay, go to step 13).
9. Check for poor terminal connections at EGR valve. Repair as necessary. After repairs, go to step 15). If connections are okay, go to next step.
10. Replace EGR valve. If EGR showed signs of excessive heat, check for restricted exhaust. Exhaust restriction may be caused by faulty injector, grounded injector circuit or faulty PCM. Repair as necessary. Also, check for contaminated oil. After replacing EGR valve, go to step 15).
11. Locate and repair short to voltage in EGR pintle position signal circuit. After repairs, go to step 15).
12. Check EGR position signal circuit for short to 5-volt reference circuit or short to control circuit. Repair as necessary. After repairs, go to step 15). If circuits are okay, go to step 14).
13. Check circuits related to EGR valve for poor terminal connections at PCM. Repair as necessary. After repairs, go to step 15). If connections are okay, go to next step.
14. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
15. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Start engine and allow it to idle. Ensure engine is at normal operating temperature. Operate vehicle within conditions required for setting this DTC. Select SPECIFIC DTC function then enter this DTC. If scan tool indicates TEST RAN AND PASSED, go to next step. If scan tool does not indicate TEST RAN AND PASSED, repeat step 2).

DTC P1441 - EVAP SYSTEM FLOW DURING NON-PURGE

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Evaporative (EVAP) emissions canister purge is controlled by a solenoid valve which allows ported vacuum to purge canister when energized (purge on) by PCM. A vacuum switch in purge line is used to detect when system is being purged. PCM supplies and reads EVAP purge vacuum switch signal. If switch is open (purge detected) when not commanded by PCM, DTC P1441 will set.

Conditions required to set DTC are

1. No IAT, MAP, ODM or TP sensor DTCs set.
2. DTC P0442 diagnostic test has passed.
3. A continuous open purge flow condition is detected during diagnostic test (fuel tank pressure decreases to less than -11 in. H2O).

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Check if DTC P1655 is also set. If DTC P1655 is set, diagnose using P1655 tests. If DTC is not set, go to next step.
3. Turn ignition off. Remove fuel filler cap. Turn ignition on. Using scan tool, observe fuel tank pressure. If fuel tank pressure is zero in. H2O, go to next step. If fuel tank pressure is not zero in. H2O, diagnose evaporative system.
4. Replace fuel filler cap. using scan tool, capture FAIL RECORD data for DTC P1441 and clear DTCs. Install EVAP pressure/purge diagnostic station to EVAP service port. Using scan tool, command EVAP vent solenoid on (closed). Attempt to pressurize EVAP system using diagnostic station. If pressure reading of 5 in. H2O can be achieved, go to next step. If pressure reading of 5 in. H2O cannot be achieved, go to step 6).
5. Maintain tank pressure at 5 in. H2O. Observe fuel tank pressure on scan tool. If fuel tank pressure is 5 in. H2O, go to next step. If fuel tank pressure is not 5 in. H2O, go to next step.
6. Check EVAP purge and source vacuum line routing and connections at EVAP purge solenoid. Repair as necessary. After repairs, go to step 9). If routing and connections are okay, go to next step.
7. Remove engine vacuum source line from EVAP purge solenoid. Connect a hand-held vacuum pump to engine vacuum side of EVAP purge solenoid and apply 15 in. Hg vacuum. If solenoid holds vacuum, see DIAGNOSTIC AIDS. If solenoid does not hold vacuum, go to next step.
8. Replace EVAP purge solenoid. After replacing solenoid, go to next step.
9. Correct EVAP purge and source vacuum line routing and connections. After repairs, go to next step.
10. Start engine. Remove fuel filler cap. Using scan tool's output tests function, select SEAL SYSTEM and activate. Replace fuel filler cap. Turn rotary switch on diagnostic station to PURGE position. Operate engine at idle while monitoring vacuum gauge on diagnostic station for a least 10 seconds. If vacuum holds at zero in. H2O while scan tool SEAL SYSTEM function is activated, system is okay. If vacuum does not hold at zero in. Hg, repeat step 3).

Check for poor connection at PCM, damaged harness, incorrect vacuum line routing, or faulty or damaged evaporative canister.

DTC P1554 - CRUISE CONTROL STATUS CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Stepper Motor Cruise Control (SMCC) module sends cruise status input to Powertrain Control Module (PCM) to indicate when cruise control is engaged. PCM monitors cruise status signal while commanding cruise control to be disengaged by grounding cruise inhibit circuit.

Following will cause PCM to inhibit cruise control operation

1. Engine not running long enough for cruise control operation.
2. Transaxle range inputs indicate Park, Neutral, Low or Reverse gear selected.
3. Engine or vehicle speed too high or too low.
4. ABS system is active for longer than 2 seconds.
5. Vehicle acceleration or deceleration rate is too high.

Conditions for setting DTC

1. PCM commanding the SMCC module to inhibit cruise control operation.
2. Cruise status input to PCM indicates that cruise is still active.
3. Conditions present longer than one second.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Check if DTC P1662 is also set. If DTC P1662 is set, diagnose DTC first. If DTC P1662 is not set, go to next step.
3. Turn ignition off. Disconnect cruise control module. Turn ignition on. Using a DVOM, check cruise control status circuit at cruise control module harness connector and ground. If voltage is greater than 7 volts, go to next step. If voltage is not greater than 7 volts, go to step 5).
4. Turn ignition off. Reconnect cruise control module harness connector. Disconnect PCM harness connector. Turn ignition on. Using a test light connected to battery voltage, probe cruise engaged status circuit at PCM harness connector. If test light illuminates, go to step 6). If test light does not illuminate, go to step 7).
5. Turn ignition off. disconnect PCM harness connector. Using a test light connected to battery voltage, probe cruise engaged status circuit at PCM harness connector. If test light illuminates, go to step 8). If test light does not illuminate, go to step 7).
6. Replace cruise control module. After replacing cruise control module, go to step 9).
7. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to step 9).
8. Locate and repair short to ground in cruise control status circuit. After repairs, go to next step.
9. Clear DTC P1554. Start engine and observe DTCs. If DTC P1554 resets, repeat step 2). If DTC P1554 is not set, repair is complete.

Disconnect and inspect PCM connector. Inspect for damaged pins, corrosion and loose wires. An intermittent problem can be caused by a poor connection, rubbed-through wire insulation or broken wire inside insulation. Reviewing FAIL RECORDS vehicle mileage since diagnostic test last failed may help determine how often condition that caused DTC to be set occurs.

DTC P1602 - EBCM/EBTCM SERIAL DATA CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

A Class II serial data communications system is used on these vehicles to allow various modules to communicate and share information with each other. Each bit of information has 2 lengths, long or short. This allows vehicle wiring to be reduced and the transmission and reception of multiple signals over a single wire. The messages carried on a Class II serial data streams are also prioritized. If two messages attempt to establish communications on the data line at the same time, the message with a higher priority will continue. The message with a lower priority will wait. If a module cannot respond to the PCM, a DTC will set.

Conditions for setting DTC

1. Ignition on.
2. System voltage greater than 8.2 volts.
3. PCM cannot communicate with EBCM.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Check if scan tool can display data from PCM. If data is displayed, go to next step. If data cannot be displayed, diagnose data link connector.
3. Check an intermittent, short, or open connection on serial data circuit to EBCM. Repair as necessary. After repairs, go to step 6). If circuit is okay, go to next step.
4. Check an intermittent, short, or open connection on serial data circuit to BFC. Repair as necessary. After repairs, go to step 6). If circuit is okay, go to next step.
5. Check for DTCs or communication with other modules. Repair as necessary. After repairs, go to next step.
6. Using scan tool, clear DTCs. Start and warm engine to normal operating temperature. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this diagnostic ran and passed, go to next step. If scan tool does not indicate that this diagnostic ran and passed, repeat step 2).
7. Check if any additional DTCs are set. Diagnose affected DTCs. If DTCs are not set, system is okay.

Attempting to start vehicle by by-passing the PASS-Lock II(R) system or substituting parts without performing the password learn procedure may set DTC P1610, P1626, P1630 or P1632.

If no password is received, DTC P1610, P1626, P1631 or P1632 may set. An intermittent may be caused by poor connection, rubbed through wire insulation or a wire broken inside the insulation.

DTC P1610 - STANDARD BODY MODULE SERIAL DATA CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

A Class II serial data communications system is used on these vehicles to allow various modules to communicate and share information with each other. Each bit of information has 2 lengths, long or short. This allows vehicle wiring to be reduced and the transmission and reception of multiple signals over a single wire. The messages carried on a Class II serial data streams are also prioritized. If two messages attempt to establish communications on the data line at the same time, the message with a higher priority will continue. The message with a lower priority will wait. If a module cannot respond to the PCM, a DTC will set.

Conditions for setting DTC

1. Ignition on.
2. System voltage greater than 8.2 volts.
3. PCM cannot communicate with EBCM.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Check if scan tool can display data from PCM. If data is displayed, go to next step. If data cannot be displayed, diagnose data link connector.
3. Check an intermittent, short, or open connection on serial data circuit to Body Function Controller (BFC). Repair as necessary. After repairs, go to step 6). If circuit is okay, go to next step.
4. Check an intermittent, short, or open connection on serial data circuit to BFC. Repair as necessary. After repairs, go to step 6). If circuit is okay, go to next step.
5. Check for DTCs or communication with other modules. Repair as necessary. After repairs, go to next step.
6. Using scan tool, clear DTCs. Start and warm engine to normal operating temperature. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this diagnostic ran and passed, go to next step. If scan tool does not indicate that this diagnostic ran and passed, repeat step 2).
7. Check if any additional DTCs are set. Diagnose affected DTCs. If DTCs are not set, system is okay.

Attempting to start vehicle by by-passing the PASS-Lock II(R) system or substituting parts without performing the password learn procedure may set DTC P1631.

If no password is received, DTC P1610, P1626 and P1631 may set. An intermittent may be caused by poor connection, rubbed through wire insulation or a wire broken inside the insulation.

DTC P1626 - THEFT DETERRENT SYSTEM FUEL ENABLE CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Vehicle Theft Deterrent (VTD) module produces a theft deterrent fuel enable signal when ignition is on and proper key resistor pellet is sensed by VTD module. Powertrain Control Module (PCM) monitors fuel enable signal during cranking.

Conditions for setting DTC

1. Engine running.
2. PCM detects fuel enable signal is not present or incorrect.
3. PCM cannot communicate with theft deterrent system.
4. Condition present longer than 2 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Using scan tool, check if DTC P1610 is also set. If DTC P1610 is set, diagnose DTC P1610 first. If DTC P1610 is not set, go to next step.
3. Check if any of vehicle theft deterrent system have been tampered with. If theft deterrent system have been tampered, go to next step. If no components were tampered, go to step 5).
4. Repair tampered components. After repairs, perform PASS-Lock(R) password learn procedure. After performing learn procedure, go to step 8).
5. If Body Function Controller (BFC) indicates that password is valid, go to next step. If BFC indicates that password is not valid, go to step 7).
6. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
7. Check for BFC related DTCs. Diagnose DTC as necessary. After repairs, go to next step.
8. Using scan tool, CLEAR INFO or CLEAR DTCS function to clear DTC. Start and warm engine to normal operating temperature. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this diagnostic ran and passed, go to next step. If scan tool does not indicate that this diagnostic ran and passed, repeat step 2).
9. Check if any additional DTCs are set. Diagnose affected DTCs. If additional DTCs are not set, system is okay.

Attempting to start vehicle by by-passing theft deterrent system or substituting part without performing the password learn procedure may set this DTC. If no password is received, DTC P1610, P1626 and P1631 may be set.

Disconnect and inspect PCM connector. Inspect for damaged pins, corrosion and loose wires. An intermittent problem can be caused by a poor connection, rubbed-through wire insulation or broken wire inside insulation. Reviewing FAIL RECORDS vehicle mileage since diagnostic test last failed may help determine how often condition that caused DTC to be set occurs.

DTC P1630 - THEFT DETERRENT SYSTEM PCM IN LEARN MODE

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Vehicle Theft Deterrent (VTD) system disables engine unless the lock cylinder is correctly engaged by a mechanical key. VTD system includes lock cylinder, ignition switch, Body Function Controller (BFC) and PCM.

When starting engine, PCM looks for a password from the BFC through the Class II serial data circuit. If password is not recognized or not present, PCM will disable engine. There are 2 tamper detection modes: no password received and incorrect or disable password received (3 invalid passwords received).

Conditions for setting DTC

1. Pass-Lock(R) II password learn procedure has been interrupted or ready to learn.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Perform Password Learn Procedure. See ANTI-THEFT SYSTEM article in ACCESSORIES/SAFETY EQUIPMENT section. Attempt to start engine. If engine starts and continues to run, go to step 5). If engine does not start or starts and then stalls, go to next step.
3. Check if VTD components has been recently replaced. If components has been replaced, repeat step 2). If components has not been replaced recently, go to next step.
4. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
5. Using scan tool, clear DTCs. Warm engine to normal operating temperature. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this DTC ran and passed, go to next step. If scan tool does not indicate that this DTC ran and passed, repeat step 2).
6. Check if additional DTC are set. Diagnose affected DTCs. If no other DTCs are set, system is okay.

Attempting to start vehicle by by-passing the theft deterrent system or substituting parts without performing the password learn procedure may set DTC. If no password is received, DTC P1610, P1626 and P1631 may set. PCM must be reflashed to allow new password to be learned if BFC is replaced. Turn ignition off for at least 30 seconds then on for PCM to learn the new BFC password.

An intermittent may be caused by poor connection, rubbed-through wire insulation or a broken wire inside insulation.

DTC P1631 - THEFT DETERRENT SYSTEM PASSWORD INCORRECT

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Vehicle Theft Deterrent (VTD) system disables engine unless the lock cylinder is correctly engaged by a mechanical key. VTD system includes lock cylinder, ignition switch, Body Function Controller (BFC) and PCM.

When starting engine, PCM looks for a password from the BFC through the Class II serial data circuit. If password is not recognized or not present, PCM will disable engine. There are 2 tamper detection modes: no password received and incorrect or disable password received (3 invalid passwords received).

Conditions for setting DTC

1. An unrecognized or no password is sent to PCM from the BFC.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Using scan tool, display DATA LIST for BFC. If scan tool indicates that Pass-Lock(R) data is valid, go to next step. If scan tool does not indicate that Pass-Lock(R) is not valid, go to step 4).
3. Perform Password Learn Procedure. See ANTI-THEFT SYSTEM article in ACCESSORIES/SAFETY EQUIPMENT section. Attempt to start engine. If engine starts and continues to run, go to step 7). If engine does not start or starts and then stalls, go to step 6).
4. Check if VTD related DTCs are set. Diagnose affected DTCs. If no other DTCs are set, go to next step.
5. Check if VTD components has been recently replaced. If components has been replaced, repeat step 2). If components has not been replaced recently, go to step 7).
6. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
7. Using scan tool, clear DTCs. Warm engine to normal operating temperature. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this DTC ran and passed, go to next step. If scan tool does not indicate that this DTC ran and passed, repeat step 2).
8. Check if additional DTC are set. Diagnose affected DTCs. If no other DTCs are set, system is okay.

Attempting to start vehicle by by-passing the theft deterrent system or substituting parts without performing the password learn procedure may set DTC. If no password is received, DTC P1610, P1626 and P1631 may set. PCM must be reflashed to allow new password to be learned if BFC or TBS is replaced. Turn ignition off for at least 30 seconds then on for PCM to learn the new BFC password.

An intermittent may be caused by poor connection, rubbed-through wire insulation or a broken wire inside insulation.

DTC P1635 - 5-VOLT REFERENCE "A" CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Powertrain Control Module (PCM) monitors 5-volt reference "A" circuit. If voltage is out of tolerance, DTC P1635 will set.

Conditions for setting DTC

1. PCM detects a voltage out of range/tolerance on the 5-volt reference circuit.
2. Condition present longer than 10 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Inspect PCM engine grounds. Ensure grounds are clean and tight. Repair as necessary. After repairs, go to step 12). If grounds are okay, go to next step.
3. Check if any other DTCs are set. If any other DTCs are set, diagnose DTCs as necessary. If multiple sensor DTCs are set, check for open or shorts in circuits common to all sensors (5-volt reference and sensor ground circuits). If no other DTCs are set, go to next step.
4. Turn ignition off. Disconnect PCM connector. Turn ignition on. Using DVOM, check voltage between sensor ground circuit and 5-volt reference "A" circuit terminals at PCM connector. If voltage is greater than 5 volts, go to next step. If voltage is not greater than 5 volts, go to step 9).
5. Ensure DVOM is still connected between sensor ground circuit and 5-volt reference "A" circuit terminals at PCM connector. Observe DVOM and disconnect EGR valve connector. If voltage is greater than 5 volts, go to next step. If voltage is not greater than 5 volts, go to step 8).
6. Observe DVOM and disconnect TP sensor connector. Again, observe DVOM and disconnect MAP sensor connector. If voltage changes when one of the sensors is disconnected, locate and repair short to voltage in suspect sensor signal circuit. After repairs, go to step 12). If voltage does not change when sensors are disconnected, go to next step.
7. Turn ignition off. Disconnect PCM connector. Turn ignition on. Check 5-volt reference "A" circuit for a short to voltage. Repair as necessary. After repairs, go to step 12). If circuit is okay, go to step 11).
8. Replace EGR valve. After replacing EGR valve, go to step 12).
9. If voltage is less than 4.5 volts, go to step 10). If voltage is not less than 4.5 volts, go to step 11).
10. Turn ignition off. Disconnect PCM connector. Check for short to ground in 5-volt reference "A" circuit. Repair as necessary. After repairs, go to step 12). If circuit is okay, go to next step.
11. Replace PCM. Program replacement PCM using required equipment. After repair is completed, go to next step.
12. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for DTC P1635 until DTC P1635 test runs. If scan tool indicates FAILED THIS IGN, repeat step 2). If scan tool does not indicate FAILED THIS IGN, repair is complete.

Disconnect and inspect PCM connector. Inspect for damaged pins, corrosion and loose wires. An intermittent problem can be caused by a poor connection, rubbed-through wire insulation or broken wire inside insulation. Reviewing FAIL RECORDS vehicle mileage since diagnostic test last failed may help determine how often condition that caused DTC to be set occurs.

DTC P1639 - 5-VOLT REFERENCE "B" CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

PCM uses 5-volt reference "B" circuit as a sensor feed for A/C refrigerant pressure sensor. PCM monitors voltage on this circuit. If PCM senses voltage out of tolerance/range, DTC P1639 sets.

Conditions required to set DTC are

1. PCM detects an out of tolerance condition on the 5-volt reference "B" circuit.
2. Condition present for longer than 10 seconds

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Ensure PCM and engine grounds are secure and clean. If a problem is found, go to step 11). If no problem is found, go to next step.
3. Using scan tool, select DTC INFO, LAST TST FAIL. If DTC P0530 also set, go to DTC P0530. If DTC is not set, go to next step.
4. Turn ignition off. Disconnect PCM connectors. Turn ignition on. Using a DVOM, check voltage between PCM harness connector ground and 5-volt reference "B" circuits. If voltage is greater than 5 volts, go to next step. If voltage is not greater than 5 volts, go to step 8).
5. Using DVOM, check voltage between PCM harness connector ground and 5-volt reference "B" circuits. Disconnect A/C refrigerant pressure sensor. If voltage is greater than 5 volts, go to next step. If voltage is not greater 5 volts, go to step 7).
6. Turn ignition off. Disconnect PCM harness connectors. Turn ignition on. Check 5-volt reference "B" circuit for short to voltage. If short to voltage is found, repair as necessary. After repairs, go to step 11). If circuit is okay, go to step 10).
7. Locate and repair short to voltage in A/C refrigerant pressure sensor signal circuit. After repairs, go to step 11).
8. If voltage is less than 4.5 volts, go to next step. If voltage is not less than 4.5 volts, go to step 10).
9. Turn ignition off. Disconnect PCM harness connectors. Turn ignition on. Check 5-volt reference "B" circuit for short to ground. If short to ground is found, repair as necessary. After repairs, go to step 11). If circuit is okay, go to next step.
10. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
11. Using scan tool, read and record FAIL RECORDS DATA, and clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, select SPECIFIC DTC INFO for DTC P1639. If scan tool displays DTC P1639 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P1639 FAILED THIS IGN, repair is complete.

Check for faulty connections or damaged harness. Observe A/C PRESSURE display on scan tool while moving harness and connectors related to A/C refrigerant pressure sensor. A change in scan tool display indicates fault location.

DTC P1641 - A/C RELAY CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Output Driver Modules (ODMs) are used by Powertrain Control Module (PCM) to turn on current driven devices that are needed to control various engine and transaxle functions. Each ODM can control up to 7 separate outputs by grounding the device that PCM is commanding on. ODMs can diagnose each output circuit individually. DTC P1641 indicates an improper voltage level has been detected on the output circuit controlling the A/C compressor control relay.

Conditions for setting this DTC

1. Ignition is on.
2. Improper voltage level detected on output circuit controlling A/C control relay.
3. Conditions present for at least 30 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Turn ignition off. Disconnect PCM connector. Turn ignition on. Using DVOM, check voltage between ground and A/C relay driver circuit terminal at PCM connector. If battery voltage is present, go to next step. If battery voltage is not present, go to step 6).
3. Set amp meter to 10-amp range. Measure current between ground and MIL driver circuit terminal at PCM connector. Monitor reading for a minimum of 2 minutes. If current is 0.1-1.5 amps, go to step 11). If current is not 0.1-1.5 amps, go to next step.
4. Turn ignition off. Disconnect instrument cluster connector. Turn ignition on. Using DVOM, check voltage between ground and A/C relay driver circuit terminal at PCM connector. If voltage is zero volts, go to step 10). If voltage is not zero volts, go to next step.
5. Locate and repair short to voltage in A/C relay driver circuit. After repairs, go to step 15).
6. Remove and inspect fuse for A/C relay. If fuse is blown, go to next step. If fuse is okay, go to step 8).
7. Locate and repair short to ground in ignition feed circuit for A/C relay. After repairs, go to step 15).
8. Disconnect instrument cluster connector. Turn ignition on. Check voltage between ground and ignition feed circuit terminal for A/C relay. If battery voltage is present, go to next step. If battery voltage is not present, go to step 13).
9. Check for an open or short to ground in A/C relay driver circuit. Repair as necessary. After repairs, go to step 15). If circuit is okay, go to next step.
10. Check A/C relay driver circuit and ignition feed circuit for poor terminal connection at PCM connector. Repair as necessary. After repairs, go to step 15). If connections are okay, go to step 14).
11. Turn ignition off. Reconnect PCM connector. Disconnect A/C relay connector. Turn ignition on. Connect a test light between affected output driver circuit and ignition feed circuit terminals at A/C relay harness connector. Using scan tool, select OUTPUTS TEST function and cycle A/C relay on and off. If test light flashes, see DIAGNOSTIC AIDS. If test light does not flash, go to next step.
12. Check A/C relay driver circuit for poor terminal connection at PCM. Repair as necessary. After repairs, go to step 15). If connection is okay, go to step 14).
13. Locate and repair open in ignition feed circuit to A/C relay. After repairs, go to step 15).
14. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
15. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for DTC P1641 until DTC P1641 test runs. If scan tool indicates FAILED THIS IGN, repeat step 2). If scan tool does not indicate FAILED THIS IGN, repair is complete.

Disconnect and inspect PCM connector. Inspect for damaged pins, corrosion and loose wires. An intermittent problem can be caused by a poor connection, rubbed-through wire insulation or broken wire inside insulation. Reviewing FAIL RECORDS vehicle mileage since diagnostic test last failed may help determine how often condition that caused DTC to be set occurs.

DTC P1651 - FAN 1 RELAY CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Output Driver Modules (ODM) are used by PCM to turn on current-driven devices needed to control various engine and transaxle functions. Each ODM can control up to 7 outputs, including fan 1 relay, by supplying ground to device PCM is commanding on. ODMs can diagnose each circuit individually. If ODM "B" output 1 (fan 1 relay driver circuit) detects an improper voltage level, P1651 is set.

Conditions required to set DTC are

1. Ignition is on.
2. An improper voltage level detected on fan 1 relay driver circuit.
3. Condition present for at least 30 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
2. Turn ignition off. Disconnect PCM harness connector. Turn ignition on. Using a DVOM, check voltage between engine ground and PCM harness connector fan 1 relay driver circuit. If voltage is about battery voltage, go to next step. If voltage is not about battery voltage, go to step 6).
3. Using DVOM in 10-amp scale, check current between engine ground and fan 1 relay driver circuit for 2 minutes. If current remains 0.1-1.5 amps go to step 11). If current does not remain 0.1-1.5 amps, go to next step.
4. Turn ignition off. Disconnect PCM harness connector. Disconnect fan 1 relay connector. Turn ignition on. Using DVOM, check voltage between engine ground and fan 1 relay driver circuit. If voltage is zero volts, go to step 10). If voltage is not zero volts, go to next step.
5. Locate and repair short to voltage in fan 1 relay driver circuit. After repairs, go to step 16).
6. Check fan 1 relay ignition feed fuse. If fuse is blown, go to next step. If fuse is okay, go to step 8).
7. Locate and repair short to ground in fan 1 relay ignition feed circuit. Replace fuse. After replacing fuse, go to step 16).
8. Disconnect fan 1 relay connector. Turn ignition on. Check voltage between engine ground and fan 1 relay ignition feed circuit. If voltage is near battery voltage, go to next step. If voltage is not as specified, go to step 13).
9. Check fan 1 relay driver circuit for open or short to ground. If a problem is found, repair as necessary. After repairs, go to step 16). If no problem is found, go to next step.
10. Check fan 1 relay driver and fan 1 relay ignition feed circuits for faulty connection at PCM. If faulty connection is found, repair as necessary. After repairs, go to step 16). If connection is okay, go to step 14).
11. Turn ignition off. Reconnect PCM connectors. Disconnect fan 1 relay connector. Turn ignition on. Connect a test light between fan 1 relay harness connector fan 1 relay driver and ignition feed circuits. Using scan tool, cycle fan 1 relay on and off. If test light flashes on and off, go to DIAGNOSTIC AIDS. If test light does not flash on and off, go to next step.
12. Check fan 1 relay driver circuit for faulty connection at PCM. If faulty connection is found, repair as necessary. After repairs, go to step 16). If connection is okay, go to step 15).
13. Locate and repair open fan 1 relay ignition feed circuit. After repairs, go to step 16).
14. Replace fan 1 relay. After replacing relay, go to step 16).
15. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
16. Using scan tool, read and record FAIL RECORDS DATA, and clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, select SPECIFIC DTC INFO for DTC P1651. If scan tool displays DTC P1651 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P1651 FAILED THIS IGN, repair is complete.

Check for faulty connections or damaged harness. Disconnect PCM connector. Turn ignition on. Connect a DVOM between engine ground and PCM harness connector fan 1 relay driver circuit. Observe DVOM while moving all related harness and connectors. A change in voltage display indicates fault location.

DTC P1652 - FAN 2 RELAY CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Output Driver Modules (ODMs) are used by Powertrain Control Module (PCM) to turn on current driven devices that are needed to control various engine and transaxle functions. Each ODM can control up to 7 separate outputs by grounding the device that PCM is commanding on. ODMs can diagnose each output circuit individually.

Conditions for setting DTC

1. Ignition is on.
2. Improper voltage level detected on ODM B output No. 2 (high speed fan relay driver circuit).
3. Conditions present for at least 30 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Turn ignition off. Disconnect PCM connector. Turn ignition on. Using DVOM, check voltage between ground and high speed fan control circuit terminal at PCM connector. If battery voltage is present, go to next step. If battery voltage is not present, go to step 7).
3. Turn ignition off. Remove cooling fans No. 2 and 3 relays. Check voltage between high speed fans control circuit and ground. If voltage reading is zero volts, go to next step. If voltage reading is not zero volts, go to step 6).
4. Replace cooling fans No. 2 and 3 relays. Set DVOM to 10-amp scale. Turn ignition on. Check current between ground and high speed fan control circuit terminal at PCM connector. Monitor reading for a minimum of 2 minutes. If current is 0.1-1.5 amps, go to step 12). If current is not 0.1-1.5 amps, go to next step.
5. Turn ignition off. Remove cooling fan 3 relay. Turn ignition on. Set DVOM to 10-amp scale. Turn ignition on. Using DVOM, check current between ground and cooling fan 3 relay control circuit at relay connector. If current reads 0.1-1.5 amps, go to step 15). If current does not read 0.1-1.5 amps, go to step 16).
6. Locate and repair short to voltage in high speed fan control circuit. After repairs, go to step 18).
7. Check battery voltage feed fuse for cooling fans No. 2 and 3 relays. If fuse is blown, go to next step. If fuse is okay, go to step 9).
8. Locate and repair short to ground in battery positive feed circuit for fan No. 3 relay. Replace fuse. After repairs, go to step 18).
9. Disconnect cooling fan No. 3 relay. Turn ignition on. Check voltage between ground and battery feed circuit terminal at cooling fan No. 3 relay connector. If battery voltage is present, go to next step. If battery voltage is not present, go to step 14).
10. Check high speed fan control circuit for open or short to ground. Repair as necessary. After repairs, go to step 18). If circuit is okay, go to next step.
11. Check output driver circuit and battery feed circuit for poor connection at cooling fan No. 3 relay and PCM. Repair as necessary. After repairs, go to step 18). If connection is okay, go to step 15).
12. Turn ignition off. Reconnect PCM connector. Disconnect cooling fan No. 3 relay connector. Turn ignition on. Using scan tool, select output test function and cycle cooling fan No. 3 relay on and off. If test light flashes on and off, see DIAGNOSTIC AIDS. If test light does not flash on and off, go to next step.
13. Check high speed fan control circuit for poor terminal connection at PCM. Repair as necessary. After repairs, go to step 18). If connection is okay, go to step 17).
14. Locate and repair open in battery feed circuit to cooling fan Nos. 2 and 3 relay, or poor terminal connection between cooling fan No. 2 Maxifuse(R) and fuse block. Repair as necessary. After repairs, go to step 18).
15. Replace cooling fan No. 3 relay. After replacing relay, go to step 18).
16. Replace cooling fan No. 2 relay. After replacing relay, go to step 18).
17. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
18. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for DTC P1652 until DTC P1652 test runs. If scan tool indicates FAILED THIS IGN, repeat step 2). If scan tool does not indicate FAILED THIS IGN, repair is complete.

Disconnect and inspect PCM connector. Inspect for damaged pins, corrosion and loose wires. An intermittent problem can be caused by a poor connection, rubbed-through wire insulation or broken wire inside insulation. Reviewing FAIL RECORDS vehicle mileage since diagnostic test last failed may help determine how often condition that caused DTC to be set occurs.

DTC P1662 - CRUISE CONTROL INHIBIT CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

Output Driver Modules (ODMs) are used by Powertrain Control Module (PCM) to turn on current driven devices that are needed to control various engine and transaxle functions. Each ODM can control up to 7 separate outputs by grounding the device that PCM is commanding on. ODMs can diagnose each output circuit individually. DTC P1662 indicates an improper voltage level has been detected on cruise inhibit driver (control) circuit.

Conditions for setting DTCs

1. Ignition on.
2. Improper voltage level detected on the cruise inhibit output driver circuit.
3. Conditions present for at least 20 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Turn ignition off. Disconnect PCM connector. Turn ignition on. Using DVOM, check voltage between ground and cruise inhibit driver circuit terminal at PCM connector. If battery voltage is present, go to next step. If battery voltage is not present, go to step 6).
3. Set ammeter to 10-amp range. Check current between ground and cruise inhibit driver circuit terminal at PCM connector. Monitor reading for a minimum of 2 minutes. If current is .5 amp, go to step 11). If current is not .5 amp, go to next step.
4. Disconnect Stepper Motor Cruise Control (SMCC) module connector. Using DVOM, check voltage between ground and cruise inhibit driver circuit at cruise inhibit harness connector. If voltage reading is zero volts, go to step 14). If voltage reading is not zero volts, go to next step.
5. Locate and repair short to voltage in cruise inhibit driver circuit. After repairs, go to step 16).
6. Remove and inspect fuse for SMCC module. If fuse is blown, go to next step. If fuse is okay, go to step 8).
7. Locate and repair short to ground in ignition feed circuit for SMCC module. Replace fuse. After repair is completed, go to step 16).
8. Disconnect SMCC module. Turn ignition on. Check voltage between ground and ignition feed circuit terminal at SMCC module harness connector. If battery voltage is present, go to next step. If battery voltage is not present, go to step 13).
9. Check for an open or short to ground in cruise inhibit driver circuit. Repair as necessary. After repairs, go to step 16). If circuit is okay, go to next step.
10. Check cruise inhibit driver circuit and ignition feed circuit for poor terminal connection at SMCC module connector and at PCM connector. Repair as necessary. After repairs, go to step 16). If connections are okay, go to step 14).
11. Turn ignition off. Reconnect PCM connector. Disconnect SMCC module connector. Turn ignition on. Connect a test light between cruise inhibit driver circuit and ignition feed circuit terminals at SMCC module harness connector. Using scan tool, select OUTPUTS TEST function and cycle cruise inhibit on and off. If test light flashes, see DIAGNOSTIC AIDS. If test light does not flash, go to next step.
12. Check cruise inhibit driver circuit for poor terminal connection at PCM. Repair as necessary. After repairs, go to step 16). If connection is okay, go to step 15).
13. Locate and repair open in ignition feed circuit to SMCC module. After repairs, go to step 16).
14. Replace SMCC module. After replacing module, go to step 16).
15. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
16. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for DTC P1655 until DTC P1655 test runs. If scan tool indicates FAILED THIS IGN, repeat step 2). If scan tool does not indicate FAILED THIS IGN, repair is complete.

Disconnect and inspect PCM connector. Inspect for damaged pins, corrosion and loose wires. An intermittent problem can be caused by a poor connection, rubbed-through wire insulation or broken wire inside insulation. Reviewing FAIL RECORDS vehicle mileage since diagnostic test last failed may help determine how often condition that caused DTC to be set occurs.

DTC P1665 - EVAP VENT SOLENOID CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

The Output Driver Module (ODM) is used by the PCM to turn on many of the current-driven devices that are needed to control various engine and transaxle functions. Each ODM is capable of controlling up to 7 separate outputs by applying ground to the device which the PCM is commanding on. ODM have the capability of diagnosing each output circuit individually.

Conditions required to set DTC are

1. Ignition is on.
2. Improper voltage level detected on output circuit controlling EVAP canister vent valve.
3. Conditions present for at least 30 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Turn ignition off. Disconnect PCM connector. Turn ignition on. Using DVOM, check voltage between ground and EVAP canister vent valve control circuit at PCM connector. If battery voltage is present, go to next step. If battery voltage is not present, go to step 6).
3. Set ammeter to 10-amp range. Check current between ground and EVAP canister vent valve control circuit at PCM connector. Monitor reading for a minimum of 2 minutes. If current is .1-.8 amp, go to step 11). If current is not .1-.8 amp, go to next step.
4. Disconnect EVAP canister vent valve connector. Using DVOM, check voltage between ground and EVAP vent valve solenoid control circuit at harness connector. If voltage reading is zero volts, go to step 14). If voltage reading is not zero volts, go to next step.
5. Locate and repair short to voltage in EVAP canister vent valve control circuit. After repairs, go to step 16).
6. Turn ignition off. Remove and inspect fuse for EVAP canister vent valve. If fuse is blown, go to next step. If fuse is okay, go to step 8).
7. Locate and repair short to ground in ignition feed circuit for EVAP canister vent valve. Replace fuse. After repairs, go to step 16).
8. Disconnect EVAP canister vent valve. Turn ignition on. Check voltage between ground and ignition feed circuit for EVAP canister vent valve harness connector. If battery voltage is present, go to next step. If battery voltage is not present, go to step 13).
9. Check for an open or short to ground in EVAP canister vent valve control circuit. Repair as necessary. After repairs, go to step 16). If circuit is okay, go to next step.
10. Check EVAP canister control circuit and ignition feed circuit for poor terminal connection at EVAP canister vent and at PCM connector. Repair as necessary. After repairs, go to step 16). If connections are okay, go to step 14).
11. Turn ignition off. Reconnect PCM harness connector. Disconnect EVAP canister vent valve connector. Turn ignition on. Connect a test light between EVAP canister vent valve control circuit and ignition feed circuit terminals at EVAP canister vent valve connector. Using scan tool, select OUTPUTS TEST function and cycle EVAP vent solenoid on and off. If test light flashes on and off, see DIAGNOSTIC AIDS. If test light does not flash, go to next step.
12. Check EVAP canister vent valve control circuit for poor terminal connection at PCM. Repair as necessary. After repairs, go to step 16). If connection is okay, go to step 15).
13. Locate and repair open in ignition feed circuit to EVAP canister vent valve. After repairs, go to step 16).
14. Replace EVAP canister vent valve. After replacing vent valve, go to step 16).
15. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
16. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for this DTC until this DTC test runs. If scan tool indicates FAILED THIS IGN, repeat step 2). If scan tool does not indicate FAILED THIS IGN, repair is complete.

Disconnect and inspect PCM and EVAP canister vent valve harness connectors. Inspect for damaged pins, corrosion and loose wires. An intermittent problem can be caused by a poor connection, rubbed-through wire insulation or broken wire inside insulation. Reviewing FAIL RECORDS vehicle mileage since diagnostic test last failed may help determine how often condition that caused DTC to set.

DTC P1671 - MIL CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

The Output Driver Module (ODM) is used by the PCM to turn on many of the current-driven devices that are needed to control various engine and transaxle functions. Each ODM is capable of controlling up to 7 separate outputs by applying ground to the device which the PCM is commanding on. ODM have the capability of diagnosing each output circuit individually.

Conditions required to set DTC are

1. Ignition is on.
2. Improper voltage level detected on output circuit controlling MIL.
3. Conditions present for at least 30 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Turn ignition off. Disconnect PCM connector. Turn ignition on. Using DVOM, check voltage between ground and MIL control circuit at PCM connector. If battery voltage is present, go to next step. If battery voltage is not present, go to step 6).
3. Set ammeter to 10-amp range. Check current between ground and MIL control circuit at PCM connector. Monitor reading for a minimum of 2 minutes. If current is .05-.50 amp, go to step 11). If current is not .05-.50 amp, go to next step.
4. Disconnect instrument panel cluster connector. Using DVOM, check voltage between ground and MIL control circuit at harness connector. If voltage reading is zero volts, go to step 10). If voltage reading is not zero volts, go to next step.
5. Locate and repair short to voltage in MIL control circuit. After repairs, go to step 15).
6. Check ignition feed fuse for instrument panel indicators. If fuse is blown, go to next step. If fuse is okay, go to step 8).
7. Locate and repair short to ground in ignition feed circuit for instrument panel indicators. Replace fuse. After repairs, go to step 15).
8. Disconnect instrument cluster connector. Turn ignition on. Check voltage between ground and ignition feed circuit for instrument cluster indicators. If battery voltage is present, go to next step. If battery voltage is not present, go to step 13).
9. Check for an open or short to ground in MIL control circuit. Repair as necessary. After repairs, go to step 15). If circuit is okay, go to next step.
10. Check MIL control circuit and ignition feed circuit for poor terminal connection at instrument cluster and at PCM connector. Repair as necessary. After repairs, go to step 15). If connections are okay, diagnose instrument cluster assembly.
11. Turn ignition off. Reconnect PCM harness connector. Disconnect instrument cluster connector. Turn ignition on. Connect a test light between MIL control circuit and ignition feed circuit terminals at instrument panel connector. Using scan tool, select OUTPUTS TEST function and cycle MIL on and off. If test light flashes on and off, see DIAGNOSTIC AIDS. If test light does not flash, go to next step.
12. Check MIL control circuit for poor terminal connection at PCM. Repair as necessary. After repairs, go to step 15). If connection is okay, go to step 15).
13. Locate and repair open in ignition feed circuit to instrument cluster indicators. After repairs, go to step 15).
14. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
15. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for this DTC until DTC test runs. If scan tool indicates FAILED THIS IGN, repeat step 2). If scan tool does not indicate FAILED THIS IGN, repair is complete.

Check for faulty connections or damaged harness. Disconnect PCM connector. Turn ignition on. Connect DVOM between engine ground and MIL control circuit at PCM harness connector. Observe DVOM while moving all related harness and connectors. A change in voltage display indicates fault location.

DTC P1676 - EVAP PURGE VALVE CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS - 3.1L article.

The Output Driver Module (ODM) is used by the PCM to turn on many of the current-driven devices that are needed to control various engine and transaxle functions. Each ODM is capable of controlling up to 7 separate outputs by applying ground to the device which the PCM is commanding on. ODM have the capability of diagnosing each output circuit individually.

Conditions required to set DTC are

1. Ignition is on.
2. Improper voltage level detected on output circuit controlling EVAP purge solenoid valve.
3. Conditions present for at least 30 seconds.

1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(/chevrolet/malibu/v-1996-2000/remont/testing-diagnostics/#engine-controls-tests-wcodes-31l__powertrain-on-board-diagnostic-obd-system-check) , then go to next step.
2. Turn ignition off. Disconnect PCM connector. Turn ignition on. Using DVOM, check voltage between ground and EVAP purge valve control circuit at PCM connector. If battery voltage is present, go to next step. If battery voltage is not present, go to step 6).
3. Set ammeter to 10-amp range. Check current between ground and EVAP purge valve control circuit at PCM connector. Monitor reading for a minimum of 2 minutes. If current is .05-.50 amp, go to step 11). If current is not .05-.50 amp, go to next step.
4. Disconnect EVAP purge valve connector. Using DVOM, check voltage between ground and EVAP purge valve control circuit at harness connector. If voltage reading is zero volts, go to step 10). If voltage reading is not zero volts, go to next step.
5. Locate and repair short to voltage in EVAP purge valve control circuit. After repairs, go to step 16).
6. Turn ignition off. Remove and inspect fuse for EVAP purge valve. If fuse is blown, go to next step. If fuse is okay, go to step 8).
7. Locate and repair short to ground in ignition feed circuit for EVAP purge vent valve. Replace fuse. After repairs, go to step 16).
8. Disconnect EVAP purge valve. Turn ignition on. Check voltage between ground and ignition feed circuit for EVAP purge valve harness connector. If battery voltage is present, go to next step. If battery voltage is not present, go to step 13).
9. Check for an open or short to ground in EVAP purge valve control circuit. Repair as necessary. After repairs, go to step 16). If circuit is okay, go to next step.
10. Check EVAP purge valve control circuit and ignition feed circuit for poor terminal connection at EVAP purge valve and at PCM connector. Repair as necessary. After repairs, go to step 16). If connections are okay, go to step 14).
11. Turn ignition off. Reconnect PCM harness connector. Disconnect EVAP purge valve connector. Turn ignition on. Connect a test light between EVAP purge valve control circuit and ignition feed circuit terminals at EVAP purge valve connector. Using scan tool, select OUTPUTS TEST function and cycle EVAP purge solenoid on and off. If test light flashes on and off, see DIAGNOSTIC AIDS. If test light does not flash, go to next step.
12. Check EVAP purge valve control circuit for poor terminal connection at PCM. Repair as necessary. After repairs, go to step 16). If connection is okay, go to step 15).
13. Locate and repair open in ignition feed circuit to EVAP purge valve. After repairs, go to step 16).
14. Replace EVAP purge valve. After replacing valve, go to step 16).
15. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
16. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for this DTC until this DTC test runs. If scan tool indicates FAILED THIS IGN, repeat step 2). If scan tool does not indicate FAILED THIS IGN, repair is complete.

See also:
• DIAGNOSTIC PROCEDURE
• POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK
• HARD OR INTERMITTENT TROUBLE CODE DETERMINATION
• P0101
• P0102
• P0103
• P0107
• P0108
• P0112
• P0113
• P0117
• P0118
• P0121
• P0122
• P0123
• P0125
• P0131
• P0132
• P0133
• P0134
• P0135
• P0137
• P0138
• P0140
• P0141
• P0171
• P0201
• P0202
• P0203
• P0204
• P0205
• P0206
• P0230
• P0325
• P0327
• P0336
• P0341
• P0403
• P0404
• P0405
• P0440
• P0442
• P0446
• P0452
• P0453
• P0506
• P0507
• P0530
• P0560
• P0705
• P0706
• P1106
• P1107
• P1111
• P1112
• P1114
• P1115
• P1121
• P1122
• P1133
• P1134
• P1336
• P1351
• P1352
• P1361
• P1374
• P1380
• P1381
• P1404
• P1441
• P1554
• P1602
• P1610
• P1626
• P1630
• P1631
• P1635
• P1639
• P1641
• P1651
• P1652
• P1662
• P1665
• P1671
• P1676
• CLEARING DIAGNOSTIC TROUBLE CODES (DTC)