Home ReviewsRefund
Home/Oldsmobile/Bravada/Oldsmobile Bravada II (1995-2001)/Repair manual/Testing & Diagnostics/Engine Controls - Tests W/codes - 4.3L: Diagnosis
Contents Wiring diagrams Section: Testing & Diagnostics All sections

Engine Controls - Tests W/codes - 4.3L: Diagnosis Oldsmobile Bravada II

Testing & Diagnostics ~41404 words

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.

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.

LAST TEST FAIL

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

TEST FAIL SCC

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

TEST RAN AND PASSED

This message indicates the selected diagnostic test has

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

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

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»(ref-33422-S03507999212001122000000) .
  2. If DTC(s) were displayed, determine whether codes are hard or intermittent trouble codes. Hard codes will cause MIL to illuminate continuously while engine is running. See «HARD OR INTERMITTENT TROUBLE CODE DETERMINATION»(ref-33422-S16166949762001122000000) . For diagnosing hard codes, proceed to appropriate DTC test. For diagnosing intermittent codes, proceed to INTERMITTENTS in TESTS W/O CODES - 4.3L article.
  3. If no DTCs are present and a driveability problem exists, refer to SYMPTOMS in TESTS W/O CODES - 4.3L article. Doing so will help identify proper system or component to check in SYSTEM/COMPONENT TESTS - 4.3L 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 - 4.3L 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 - 4.3L article and SCAN TOOL USAGE.

  1. Turn ignition on, engine off. Observe Malfunction Indicator Light (MIL). If MIL illuminates, go to next step. If MIL does not illuminate, go to MALFUNCTION INDICATOR LIGHT (MIL).
  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 VCM data, go to next step. If scan tool does not display VCM data, go to DLC DIAGNOSIS OR NO SCAN TOOL DATA.
  3. Using scan tool, command MIL to turn off. If MIL turns off, go to next step. If MIL does not turn off, go to MALFUNCTION INDICATOR LIGHT (MIL).
  4. Using scan tool, observe DTC status for MIL REQUEST, FAIL THIS IGN, LAST TST FAIL and HISTORY. If any DTC is stored, save freeze frame and fail record information using scan tool CAPTURE INFO feature. If any DTC(s) is present, refer to affected DTC to diagnose problem. If DTC(s) is not present, go to next step.
  5. Crank engine for 10 seconds. If engine starts, go to next step. If engine does not start, go to NO START DIAGNOSIS in BASIC TESTING - 4.3L article.
  6. Compare scan tool engine data with actual control system data values. If value is within limits, go to TESTS W/O CODES - 4.3L article. If value is not within limits, go to SYSTEM/COMPONENT TESTS - 4.3L article.

DLC DIAGNOSIS OR NO SCAN TOOL DATA

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) , then go to next step.
  2. Using a test light connected to ground, probe DLC battery feed circuit. See WIRING DIAGRAMS - 4.3L article. If test light illuminates, go to next step. If test light does not illuminate, go to step 11).
  3. Using a test light connected to battery voltage, probe DLC ground circuit. See WIRING DIAGRAMS - 4.3L article. If test light illuminates on both circuits, go to next step. If test light does not illuminate on both circuits, go to step 12).
  4. Check cigarette lighter for power. If power is present at cigarette lighter, go to next step. If power is not present at cigarette lighter, go to step 13).
  5. Install and check scan tool operation on another vehicle. If scan tool operates, go to next step. If scan tool does not operate, go to step 14).
  6. Using DVOM connected to ground, check voltage of DLC serial data line circuit. See WIRING DIAGRAMS - 4.3L article. If voltage is less than 7 volts, go to next step. If voltage is not less than 7 volts, go to step 16).
  7. Using DVOM connected to ground, again check voltage of DLC serial data line circuit. If voltage is less than one volt, go to next step. If voltage is not less than one volt, go to step 16).
  8. Turn ignition off. Using DVOM connected to ground, check resistance of DLC serial data line circuit. If resistance is less than 10 milliohms, go to next step. If resistance is not less than 10 milliohms, go to step 10).
  9. Disconnect VCM connectors. Using DVOM connected to ground, check resistance of DLC serial data line circuit. If resistance is less than 10 milliohms, go to step 17). If resistance is not less than 10 milliohms, go to step 15).
  10. Repair open in serial data line circuit. After repairs, go to step 18).
  11. Repair open in DLC battery feed circuit. After repairs, go to step 18).
  12. Repair open in circuit that did not cause test light to illuminate. After repairs, go to step 18).
  13. Repair cigarette lighter. After repairs, go to step 18).
  14. Repair or replace faulty scan tool and/or cables. After repairs, go to step 18).
  15. Repair short to ground in serial data line circuit. After repairs, go to step 18).
  16. Repair short to voltage in serial data line circuit. After repairs, go to step 18).
  17. Replace VCM. Reprogram replacement VCM. After replacing VCM, go to next step.
  18. Using scan tool, select DTC, CLEAR INFO function. Attempt to start engine. If engine starts and continues to run, go to next step. If engine does not start, or starts and dies/stalls, go to step 2).
  19. Warm engine to normal operating temperature. Using scan tool, select DTC, FAILED THIS IGN function. If any DTC(s) are present, diagnose DTC. If DTC(s) are not present, go to next step.
  20. Select CAPTURE INFO, REVIEW INFO function. If additional DTC(s) are displayed, diagnose DTC. If DTC(s) are not present, system is okay.

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 DEFINITION

Code No.Circuit Affected
P0101MAF System Performance
P0102MAF Sensor Circuit Low Frequency
P0103MAF Sensor Circuit High Frequency
P0106MAP Sensor System Performance
P0107MAP Sensor Circuit Low Voltage
P0108MAP Sensor Circuit High Voltage
P0112IAT Sensor Circuit Low Voltage
P0113IAT Sensor Circuit High Voltage
P0117ECT Sensor Circuit Low Voltage
P0118ECT Sensor Circuit High Voltage
P0121TP Sensor System Performance
P0122TP Sensor Circuit Low Voltage
P0123TP Sensor Circuit High Voltage
P0125ECT Excessive Time To Reach Closed Loop
P0131HO2S Circuit Low Voltage-Bank 1, Sensor 1
P0132HO2S Circuit High Voltage-Bank 1, Sensor 1
P0133HO2S Slow Response-Bank 1, Sensor 1
P0134HO2S Insufficient Activity-Bank 1, Sensor 1
P0135HO2S Heater Circuit-Bank 1, Sensor 1
P0143HO2S Circuit Low Voltage-Bank 1, Sensor 3
P0144HO2S Circuit High Voltage-Bank 1, Sensor 3
P0146HO2S Insufficient Activity-Bank 1, Sensor 3
P0147HO2S Heater Circuit-Bank 1, Sensor 3
P0151HO2S Circuit Low Voltage-Bank 2, Sensor 1
P0152HO2S Circuit High Voltage-Bank 2, Sensor 1
P0153HO2S Slow Response-Bank 2, Sensor 1
P0154HO2S Insufficient Activity-Bank 2, Sensor 1
P0155HO2S Heater Circuit-Bank 2, Sensor 1
P0171Fuel Trim System Lean-Bank 1
P0172Fuel Trim System Rich-Bank 1
P0174Fuel Trim System Lean-Bank 2
P0175Fuel Trim System Rich-Bank 2
P0300Engine Misfire Detected
P0325Knock Sensor Circuit
P0327Knock Sensor Low Voltage
P0336CKP Sensor Circuit Performance
P0337CKP Sensor Circuit Low Frequency
P0338CKP Sensor Circuit High Frequency
P0339CKP Sensor Circuit Intermittent
P0340CKP Sensor Circuit
P0341CMP Sensor Circ. Performance
P0401EGR System Flow Insufficient
P0404EGR Valve Pintle Position
P0405EGR Valve Sensor Circuit Low Voltage
P0420TWC System Low Efficiency-Bank 1
P0440EVAP System
P0442EVAP System-Small Leak Detected
P0446EVAP System Canister Vent Blocked
P0452Fuel Tank Pressure Sensor-Low Voltage
P0453Fuel Tank Pressure Sensor-High Voltage
P0461Fuel Level Sensor Circuit Performance
P0462Fuel Level Sensor Circuit-Voltage Low
P0463Fuel Level Sensor Circuit-Voltage High
P0500Vehicle Speed Sensor Circuit
P0506IAC System-RPM Low
P0507IAC System-RPM High
P0602VCM Not Programmed
P0604VCM RAM Performance
P0605VCM Read Only Memory
P0704Clutch Switch Circuit
P1106MAP Sensor Circ. Intermittent High Voltage
P1107MAP Sensor Circ. Intermittent Low Voltage
P1111IAT Sensor Circ. Intermittent High Voltage
P1112IAT Sensor Circ. Intermittent Low Voltage
P1114ECT Sensor Circ. Intermittent Low Voltage
P1115ECT Sensor Circ. Intermittent High Voltage
P1121TP Sensor Voltage Intermittent High
P1122TP Sensor Voltage Intermittent Low
P1133HO2S Insufficient Switching-Bank 1, Sensor 1
P1134HO2S Transition Time Ratio-Bank 1, Sensor 1
P1153HO2S Insufficient Switching-Bank 2, Sensor 1
P1154HO2S Transition Time Ratio-Bank 2, Sensor 1
P1336CKP System Variation Not Learned
P1345CKP/CMP Sensor Correlation
P1351IC Circuit High Voltage
P1361IC Circuit Low Voltage
P1380EBCM/EBTCM DTC Detected Rough Road Data Unstable
P1381Misfire Detected-No EBCM/PCM/VCM Serial Data
P1404EGR Closed Pintle Position
P1441EVAP System Flow During Non-Purge
P1508IAC System-Low RPM
P1509IAC System-High RPM
P1621PCM/VCM Memory Performance
P1626Loss Of Serial Communication W/VTD
P1631Theft Deterrent System Password Incorrect
U1026Loss Of ATCM Communication
U1041Loss Of EBCM Communication
U1064Loss Of BCM/TBC/VTD Communication

TROUBLE CODE DEFINITION

HARD OR INTERMITTENT TROUBLE CODE DETERMINATION

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

  1. Enter diagnostic mode. Read and record all stored DTCs. Exit diagnostic mode, and clear DTCs. See «CLEARING DIAGNOSTIC TROUBLE CODES (DTC)»(ref-33422-S18561312152001122000000) .
  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.

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.

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.

Diagnostic Procedures

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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, with engine off. Using scan tool, monitor MAP sensor display. If MAP sensor value is greater than 100 kPa, go to next step. If MAP sensor value is not greater than 100 kPa, go to step 20). NOTE: Always replace MAP sensor seal when sensor is removed.
  3. Remove MAP sensor from intake manifold. Leave sensor connector connected. Connect a hand-held vacuum pump to MAP sensor. Slowly apply vacuum to sensor (up to 20 in. Hg). Observe MAP sensor reading on scan tool. Each inch of vacuum applied to sensor should result in 3-4 kPa drop in MAP sensor value. Value should change smoothly with each vacuum increment. If MAP sensor value changes smoothly, go to next step. If MAP sensor value does not change smoothly or is erratic, go to step 20).
  4. Apply 20 in. Hg to MAP sensor. If scan tool reads 34 kPa or less, go to next step. If scan tool does not read 34 kPa or less, go to step 20).
  5. Disconnect vacuum source from MAP sensor. If MAP sensor reading returns to original value, go to next step. If MAP sensor reading does not return to original reading, go to step 20).
  6. Turn ignition on, engine off. Using scan tool, read and record FAIL RECORD data. Operate vehicle within conditions noted in FAIL RECORD data. Using scan tool, read SPECIFIC DTC. If scan tool displays 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.
  7. Check for throttle body inlet screen blockage. Check for vacuum leaks at intake manifold, throttle body or EGR valve flange and pipes. Check for crankcase valve faulty, missing or incorrectly installed. Repair faulty conditions as necessary. After repairs, go to step 22). If no faulty conditions exist, go to next step.
  8. Turn ignition on, throttle closed. Using scan tool, read TP ANGLE value. If scan tool displays about zero percent, go to next step. If scan tool does not display zero percent, go to DTC P0121 for diagnosis.
  9. Turn ignition off. Disconnect MAF sensor harness connector. Turn ignition on, engine off. Using a DVOM, check voltage between MAF sensor harness connector signal circuit and chassis ground. If voltage is about 5 volts, go next step. If voltage is not as specified, go to step 11).
  10. Connect a test light between MAF sensor harness connector ignition feed and ground circuits. If test light illuminates, go to step 14). If test light does not illuminate, go to step 13).
  11. If voltage is less than 4.5 volts, go to step 15). If voltage is not less than 4.5 volts, go to next step.
  12. Turn ignition off. Disconnect VCM connectors. Turn ignition on, engine off. Check voltage between VCM harness connector MAF signal circuit and chassis ground. If voltage reading is about zero volts, go to step 21). If voltage is not about zero volts, go to step 18)
  13. Connect test light between MAF sensor harness connector ignition feed circuit and chassis ground. If test light illuminates, go to step 16). If test light does not illuminate, go to step 17).
  14. Check for faulty connection at MAF sensor. Repair as necessary. After repairs, go to step 22). If connection is okay, go to step 17).
  15. Check MAF sensor signal circuit between VCM and MAF sensor for open or shorted circuit to ground. Repair as necessary. After repairs, go to step 22). If circuit is okay, go to step 21).
  16. Repair open in the MAF sensor ground circuit. After repairs, go to step 22).
  17. Repair open MAF sensor ignition feed circuit. After repairs, go to step 22).
  18. Repair short to voltage in MAF sensor signal circuit. After repairs, go to step 22).
  19. Replace MAF sensor. After replacing sensor, go to step 22).
  20. Replace MAP sensor. After replacing sensor, go to step 22).
  21. Replace VCM. Program replacement VCM using required equipment. Perform password learn procedures. After replacing VCM, go to next step.
  22. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set DTC. If scan tool displays RAN AND PASSED, go to next step. If scan tool does not display RAN AND PASSED, return to step 2).
  23. Using scan tool, display CAPTURE INFO and REVIEW CAPTURE INFO function. If any additional DTCs are set, diagnose affected DTCs. If no additional DTCs are set, system is okay.

Check for stuck or faulty Throttle Position (TP) sensor. Using scan tool, read TP ANGLE value with throttle closed. If value is not zero percent, check for and repair the following condition(s)

  1. Throttle plate sticking or excessive deposits on throttle plate or throttle bore.
  2. TP sensor signal circuit shorted to voltage.
  3. Faulty connection or high resistance in TP sensor ground circuit.

If none of the listed conditions exist and TP ANGLE value is not zero percent, replace TP sensor.

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 harness and connectors. A change in scan tool display indicates fault location.

Check for plugged intake air duct or dirty air filter. A wide-open throttle acceleration from a stop should cause MAF reading on scan tool to increase from about 5-7 grams at idle to about 100 grams or greater at time of 1-2 shift. If MAF reading does not increase, check for restriction.

Check for a skewed MAP sensor, which can cause Barometric (BARO) pressure reading to be incorrectly calculated. This condition may also cause high Idle Air Control (IAC) counts. If IAC counts are high, replace MAP sensor.

Check for vacuum leaks at following locations

  1. Air inlet duct between MAF sensor and throttle body.
  2. "O" rings at fuel meter body.
  3. Oil cap and dipstick tube.
  4. Purge solenoid.
  5. MAP sensor.
  6. Brake booster.
  7. Intake manifold, crankcase, throttle body and EGR gaskets.
  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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. With engine at idle, read MAF value using scan tool. If MAF value is less than 2 gm/s, go to step 4). If value is not less than 2 gm/s, 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 RECORD data. Using scan tool, read SPECIFIC DTC. If scan tool indicates that this DTC FAILED THIS IGN, go to next step. If scan tool does not indicate that this DTC FAILED THIS IGN, see DIAGNOSTIC AIDS.
  4. Check MAF fuse. If use is open, go to step 11). If fuse is okay, go to next step.
  5. Check for blockage in MAF sensor inlet screen. Check for vacuum leaks at intake manifold, throttle body or EGR valve flange and pipes. Check for crankcase valve faulty, missing or incorrectly installed. Repair as necessary. After repairs, go to step 16). If no faulty conditions exist, go to next step.
  6. Turn ignition off. Disconnect MAF sensor harness connector. Turn ignition on, engine off. Using a DVOM, check voltage between MAF sensor harness connector signal circuit and chassis ground. If voltage is about 5 volts, go next step. If voltage is not about 5 volts, go to step 10).
  7. Connect a test light between MAF sensor harness connector ignition feed and ground circuits. If test light illuminates, go to step 9). If test light does not illuminate, go to next step.
  8. Connect test light between MAF sensor harness connector ignition feed circuit and battery ground. If test light illuminates, go to step 12). If test light does not illuminate, go to step 13).
  9. Check for faulty connection at MAF sensor. Repair as necessary. After repairs are complete, go to step 16). If connection is okay, go to step 14).
  10. Check MAF sensor signal circuit between VCM and MAF sensor for open or short in circuit. Repair as necessary. After repairs, go to step 16). If circuit is okay, go to step 15).
  11. Repair short to ground in MAF ignition voltage circuit. Replace fuse. After repairs, go to step 16).
  12. Repair open in MAF sensor ground circuit. After repairs, go to step 16).
  13. Locate and repair open MAF sensor ignition feed circuit. After repairs, go to step 16).
  14. Replace MAF sensor. After replacing sensor, go to step 16).
  15. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  16. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set DTC. If scan tool displays RAN AND PASSED, go to next step. If scan tool does not display RAN AND PASSED, repeat step 2).
  17. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.

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 appears okay, observe scan tool while moving all related harness and connectors. A change in scan tool display/reading indicates fault location.

Check for vacuum leaks at following locations

  1. Air inlet duct between MAF sensor and throttle body.
  2. "O" rings at fuel meter body.
  3. Oil cap and dipstick tube.
  4. Purge solenoid.
  5. MAP sensor.
  6. Brake booster.
  7. Intake manifold, crankcase, throttle body and EGR gaskets.
  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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. With engine at idle, use scan tool to read MAF value. If MAF value is greater than 20 gm/s, go to step 4). If MAF value is not greater than 20 gm/s, 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 RECORD data. Using scan tool, read SPECIFIC DTC. If scan tool displays that this DTC FAILED THIS IGN, go to next step. If scan tool does not indicate that this DTC FAILED THIS IGN, see DIAGNOSTIC AIDS.
  4. Turn ignition off. Disconnect MAF sensor harness connector. Start and allow engine to idle. Using scan tool, read MAF value. If value is about 0 gm/s, go to next step. If value is not 0 gm/s, go to step 7).
  5. Check for faulty connection at MAF sensor. Repair as necessary. After repairs, go to step 10). If connection is okay, go to next step.
  6. Replace MAF sensor. After replacing sensor, go to step 10).
  7. Ensure MAF sensor harness is not routed too close to high-voltage wires, such as spark plug cables, ignition coils or other high-voltage components. Reroute harness if necessary and then go to step 10). If harness routing is okay, go to next step.
  8. Check MAF sensor signal circuit connection at VCM. Repair as necessary. After repairs, go to step 10). If connection is okay, go to next step.
  9. Replace VCM. Program replacement PCM using required equipment. After replacing VCM, go to next step.
  10. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  11. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

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 harness and connectors. A change in scan tool display indicates fault location. Check for vacuum leaks at following locations

  1. Air inlet duct between MAF sensor and throttle body.
  2. "O" rings at fuel meter body.
  3. Oil cap and dipstick tube.
  4. Purge solenoid.
  5. MAP sensor.
  6. Brake booster.
  7. Intake manifold, crankcase, throttle body and EGR gaskets.
  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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 MAP voltage is plus or minus 0.4 volt of typical scan tool data, go to next step. If MAP voltage is not plus or minus 0.4 volt of typical scan tool data, go to step 6).
  3. Disconnect and plug MAP sensor vacuum source. Connect a hand-held vacuum pump to MAP sensor. Start engine. Using scan tool, read and record MAP sensor voltage. Observe and record MAP sensor voltage while applying 10 in. Hg to sensor. If difference between first and second reading is greater than 1.5 volts, see DIAGNOSTIC AIDS. If difference is not greater than 1.5 volts, go to next step.
  4. Check for faulty connection at MAF sensor. If connection is faulty, go to next step. If connection is okay, go to step 6).
  5. Repair connection as necessary. After repairs, go to step 7).
  6. Replace MAP sensor. After replacing sensor, go to next step.
  7. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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. Using scan tool, select Read and Record INFO in REVIEW INFO function. If additional DTCs are present, diagnose affected DTCs. If no additional DTCs are present, system is okay.

Check MAP sensor vacuum source for leaks, restrictions or faulty connections.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Warm engine to normal operating temperature. Operate engine at idle. Using scan tool, read MAP sensor voltage. If voltage reading is less than 0.25 volt, go to next step. If voltage is not less than 0.25 volt, go to step 5).
  3. Turn ignition off. Disconnect MAP sensor harness connector. Connect a jumper wire between MAP sensor harness connector 5-volt reference circuit and signal circuit. Turn ignition on. If voltage is greater than 4.7 volts, go to step 6). If voltage is not greater than 4.7 volts, go to next step.
  4. 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 greater than 4.7 volts, go to step 9). If voltage is not greater than 4.7 volts, go to step 7).
  5. DTC is intermittent. Check if additional DTCs are set. If additional DTCs are set, diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  6. Check for faulty MAP sensor connection. If MAP sensor connection is faulty, go to step 12). If connection is okay, go to step 11).
  7. Check for open MAP sensor signal circuit. If MAP signal circuit is open, go to step 12). If circuit is okay, go to next step.
  8. Check MAP sensor signal circuit for short to ground. If circuit is shorted, go to step 12). If circuit is okay, go to step 13).
  9. Check for open MAP sensor 5-volt reference circuit. If circuit is open, go to step 12). If circuit is okay, go to next step.
  10. Check MAP sensor 5-volt reference circuit for short to ground. If circuit is shorted, go to step 12). If circuit is okay, go to step 13).
  11. Replace MAP sensor. After replacing sensor, go to step 14).
  12. Repair circuit as necessary. After repairs, go to step 14).
  13. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  14. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  15. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.

Check MAP sensor signal and 5-volt reference circuits for intermittent open condition. With ignition on and engine off, MAP signal is equal to atmospheric pressure with signal voltage high. This information is used by VCM as an indication of altitude. Comparison of this reading with a known-good vehicle with same sensor is a way to check accuracy of suspect sensor. Reading should be within 0.4 volt. Disconnect sensor from bracket and twist sensor by hand to check for intermittents. Output changes greater than 0.1 volt indicate a faulty sensor connection.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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. Start and allow engine to idle. Using scan tool, read MAP sensor voltage. If voltage is greater than 4 volts, go to next step. If voltage is not greater than 4 volts, go to step 4).
  3. Turn ignition off. Disconnect MAP sensor harness connector. Turn ignition on. If voltage is less than one volt, go to step 5). If voltage is not less than one volt, go to step 10).
  4. DTC is intermittent. Check if any additional DTCs are set. If additional DTCs are set, diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  5. Using DVOM, check voltage between ground and 5-volt reference circuit at MAP sensor harness connector. If voltage reading is greater than 5.2 volts, go to step 11). If voltage reading is not greater than 5.2 volts, go to next step.
  6. Check if DTCs P0113, P1106 and P1111 are set. If these DTCs are set, go to step 16). If these DTCs are not set, go to next step.
  7. Using a test light connected battery voltage, probe MAP sensor ground circuit at MAP sensor harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 15).
  8. Check MAP sensor vacuum source for restriction. If restriction is found, go to step 17). If no restriction is found, go to next step.
  9. Replace MAP sensor. After replacing sensor, go to step 21).
  10. Check for short to voltage in MAP sensor signal circuit. Repair as necessary. After repairs, go to step 17). If circuit is okay, go to step 20).
  11. Turn ignition off. Disconnect VCM Gray harness connector. Turn ignition on. Using DVOM connected to ground, check voltage on 5-volt reference circuit at VCM harness connector. If voltage reading is greater than zero volts, go to next step. If voltage reading is not greater than zero volts, go to step 14).
  12. Disconnect EGR harness connector. Check voltage on 5-volt reference circuit at VCM harness connector. If voltage reading is greater than zero volts, go to next step. If voltage reading not greater than zero volts, go to step 18).
  13. Repair short to voltage on 5-volt reference circuit. After repairs, go to step 21).
  14. Using DVOM connected to ground, check voltage on VCM harness connector terminal No. 12. If voltage reading is greater than 5.2 volts, go to step 19). If voltage reading is not greater than 5.2 volts, go to step 20).
  15. Repair MAP sensor ground circuit. After repairs, go to step 21).
  16. Repair sensor ground circuit between VCM and splice. After repairs, go to step 19).
  17. Repair as necessary. After repairs, go to step 21).
  18. Replace EGR valve. After replacing EGR valve, go to step 21).
  19. Repair short to voltage on 5-volt reference circuit. After repairs, go to step 21).
  20. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  21. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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, return to step 2).
  22. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

Check MAP sensor signal and 5-volt reference circuits for intermittent open condition. With ignition on and engine off, MAP signal is equal to atmospheric pressure with signal voltage high. This information is used by VCM as an indication of altitude. Comparison of this reading with a known-good vehicle with same sensor is a way to check accuracy of suspect sensor. Readings should be within 0.4 volt of each other.

Disconnect sensor from bracket and twist sensor by hand to check for intermittents. Output changes greater than 0.1 volt indicate a faulty sensor connection.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Start and allow engine to idle. Using scan tool, read IAT sensor voltage. If voltage is less than 0.82 volt, go to next step. If voltage is not less than 0.82 volt, go to step 5).
  3. Turn engine off. Turn ignition on. Disconnect IAT sensor harness connector. If IAT sensor voltage is greater than 4 volts, go to step 7). If IAT sensor voltage is not greater than 4 volts, go to next step.
  4. Turn ignition off. Using DVOM, check resistance across IAT sensor harness connector. If resistance is infinite, go to step 8). If resistance is not infinite, go to step 6).
  5. DTC is intermittent. Check if any additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  6. Repair short to ground in IAT sensor signal circuit. After repairs, go to step 9).
  7. Replace IAT sensor. After replacing sensor, go to step 9).
  8. Replace VCM. Program replacement VCM using required equipment. After replacing and reprogramming VCM, go to next step.
  9. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  10. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.

If DTC P1112 is also set, problem is intermittent. Check for short to ground in IAT sensor harness connector signal circuit. Observe 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.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Start and allow engine to idle. Using scan tool, read IAT sensor voltage. If voltage is greater than 4.9 volts, go to next step. If voltage is not greater than 4.9 volts, go to step 6).
  3. Turn engine off. Turn ignition on. Disconnect IAT sensor harness connector. Connect a jumper wire across IAT sensor harness connector. If voltage is less than 0.82 volt, go to step 5). If voltage is not less than 0.82 volt, go to next step.
  4. Connect jumper wire between IAT sensor harness connector signal circuit and chassis ground. If voltage is less than 0.82 volt, go to step 8). If voltage is not less than 0.82 volt, go to step 9).
  5. Check voltage between IAT sensor signal circuit and a known-good ground. If voltage reading is greater than 5.2 volts, go to step 10). If voltage reading is not greater than 5.2 volts, go to next step.
  6. DTC is intermittent. Check if any additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  7. Inspect VCM and IAT sensor for proper connection. If a problem is found, go to step 11). If connections are okay, go to step 12).
  8. Check IAT sensor harness connector ground circuit for open between VCM and IAT sensor. If circuit is open, go to step 11). If circuit is okay, go to step 13).
  9. Check IAT sensor harness connector signal circuit for open between VCM and IAT sensor. If circuit is open, go to step 11). If circuit is okay, go to step 13).
  10. Repair short to voltage in IAT sensor signal circuit. After repairs, go to step 14).
  11. Repair circuit as necessary. After repairs, go to step 14).
  12. Replace IAT sensor. After replacing sensor, go to step 14).
  13. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  14. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  15. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.

If DTC P1112 is also set, problem is intermittent. Check for short to ground in IAT sensor harness connector signal circuit. Observe 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.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Start and allow engine to idle. Using scan tool, monitor ECT sensor voltage. If voltage is less than 0.25 volt, go to next step. If voltage is not less than 0.25 volt, go to step 5).
  3. Turn engine off. Turn ignition on. Disconnect ECT sensor harness connector. If voltage is greater than 4 volts, go to step 7). If voltage is not greater than 4 volts, go to next step.
  4. Turn ignition off. Using DVOM, check resistance across ECT sensor harness connector. If resistance is infinite, go to step 8). If resistance is not infinite, go to step 6).
  5. DTC is intermittent. Check if any additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  6. Repair short to ground in ECT sensor signal circuit. After repairs, go to step 9).
  7. Replace ECT sensor. After replacing sensor, go to step 9).
  8. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  9. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  10. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.

Check for short to ground in ECT sensor harness connector 5-volt reference circuit. Observe scan tool while moving all related harness and connectors. A change in scan tool display indicates fault location.

Check for skewed ECT sensor. See ECT TEMPERATURE-TO-RESISTANCE VALUES table.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Start and allow engine to idle. Using scan tool, read ECT sensor voltage. If voltage is greater than 4.9 volts, go to next step. If voltage is not greater than 4.9 volts, go to step 6).
  3. Turn engine off. Turn ignition on. Disconnect ECT sensor harness connector. Connect a jumper wire across ECT sensor harness connector. If voltage is less than 0.82 volt, go to step 5). If voltage is not less than 0.82 volt, go to next step.
  4. Connect jumper wire between ECT sensor harness connector signal circuit and chassis ground. If voltage is less than 0.82 volt, go to step 8). If voltage is not less than 0.82 volt, go to step 9).
  5. Check voltage between ground and ECT sensor circuit. If voltage is greater than 5.2 volts, go to step 10). If voltage is not greater than 5.2 volts, go to step 7).
  6. DTC is intermittent. Check if any additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, go to DIAGNOSTIC AIDS.
  7. Inspect VCM and ECT sensor for proper connection. If a problem is found, go to step 11). If connections are okay, go to step 13).
  8. Check ECT sensor harness connector ground circuit for open between VCM and ECT sensor. If circuit is open, go to step 11). If circuit is okay, go to step 14).
  9. Check ECT sensor harness connector signal circuit for open between VCM and ECT sensor. If circuit is open, go to step 11). If circuit is okay, go to step 14).
  10. Repair short to voltage in ECT sensor signal circuit. After repairs, go to step 12).
  11. Repair circuit as necessary. After repairs, go to step 15).
  12. Reconnect ECT harness connector. Start engine. Using scan tool, monitor ECT sensor voltage. If ECT sensor voltage is less than 4.9 volts, go to step 15). If ECT sensor voltage is not less than 4.9 volts, go to next step.
  13. Replace ECT sensor. After replacing sensor, go to step 15).
  14. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  15. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  16. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.

Check for faulty connections or open in 5-volt reference and ground circuits. Check for skewed ECT sensor. See ECT TEMPERATURE-TO-RESISTANCE VALUES table.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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 TP ANGLE value. If value is greater than 2 percent, go to step 4). If value is not greater than 2 percent, go to next step.
  3. Observe scan tool while moving throttle from closed to wide open, and closed again. If TP ANGLE value is greater than 2 percent, go to next step. If value is 2 percent or less, go to step 5).
  4. Disconnect TP sensor harness connector. If TP ANGLE value is zero percent, go to step 6). If value is not zero percent, go to step 9).
  5. DTC is intermittent. Check if any additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, go to DIAGNOSTIC AIDS.
  6. Check for faulty connection at TP sensor. Repair as necessary. After repairs, go to next step. If connection is okay, go to step 8).
  7. Repair circuit as necessary. After repairs, go to step 10).
  8. Replace TP sensor. After replacing sensor, go to step 10).
  9. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  10. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  11. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.

Check for and repair the following condition(s)

  1. Throttle plate sticking or excessive deposits on throttle plate or throttle bore.
  2. Check TP sensor harness connector terminals for damage.
  3. A steady throttle movement from a stop should cause TP ANGLE value reading on scan tool to increase smoothly as throttle is opened.
  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Close throttle. Using scan tool, read TP signal voltage. If voltage is less than 0.15 volt, go to next step. If voltage is not less than 0.15 volt, go to step 5).
  3. Disconnect TP sensor harness connector. Connect a jumper wire between TP sensor harness connector sensor signal and 5-volt reference circuits. If voltage is greater than 4 volts, go to step 12). If voltage is not greater than 4 volts, go to next step.
  4. Connect a test light between TP sensor harness connector signal circuit and battery voltage. If scan tool reading is greater than 4 volts, go to step 6). If scan tool reading is not greater than 4 volts, go to step 8).
  5. DTC is intermittent. Check if any additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  6. Check for open in TP sensor harness connector 5-volt reference circuit. If circuit is open, go to step 11). If circuit is okay, go to next step.
  7. Check for short to ground in TP sensor harness connector 5-volt reference circuit. If circuit is shorted, go to step 11). If circuit is okay, go to step 10).
  8. Check for open in TP sensor harness connector signal circuit. If circuit is open, go to step 11). If circuit is okay, go to next step.
  9. Check for short to ground in TP sensor harness connector signal circuit. If circuit is shorted, go to step 11). If circuit is okay, go to next step.
  10. Check for faulty connection at VCM. If connection is faulty, go to next step. If connection is okay, go to step 14).
  11. Repair circuit as necessary. After repairs, go to step 15).
  12. Check TP sensor connection for looseness, damage or contamination. If problem is found, go to next step.
  13. Replace TP sensor. After replacing sensor, go to step 14).
  14. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  15. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  16. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.

Check for and repair the following condition(s)

  1. Throttle plate sticking or excessive deposits on throttle plate or throttle bore.
  2. Check TP sensor harness connector 5-volt reference circuit for open or short to ground, and repair as necessary.
  3. TP signal voltage reading on scan tool should be less than 1.25 volt with throttle closed, and greater than 4.5 volts at wide open throttle.
  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Close throttle. Using scan tool, read TP signal voltage. If voltage is greater than 4.8 volts, go to next step. If voltage is not greater than 4.8 volts, go to step 4).
  3. Turn ignition off. Disconnect TP sensor harness connector. Turn ignition on. Using scan tool check TP sensor voltage reading. If voltage reading is less than 0.2 volt, go to step 5). If voltage is not less than 0.2 volt, go to step 8).
  4. DTC is intermittent. Check if additional DTCs are present. If additional DTCs are present, diagnose affected DTCs. If no other DTCs are present, see DIAGNOSTIC AIDS.
  5. Using DVOM connected to ground, probe 5-volt reference circuit at TP sensor harness connector. If voltage reading is greater than 5.2 volts, go to step 9). If voltage reading is not greater than 5.2 volts, go to next step.
  6. Using a test light connected to battery voltage, probe TP sensor ground circuit at TP sensor harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 13).
  7. Replace TP sensor. After replacing sensor, go to step 18).
  8. Check for short to voltage on TP sensor signal circuit. Repair as necessary. After repairs, go to step 14). If circuit is okay, go to step 17).
  9. Turn ignition off. Disconnect VCM Gray harness connector. Turn ignition on. Using DVOM connected to ground, check voltage on the 5-volt reference circuit at the VCM harness connector. If voltage reading is greater than 5.2 volts, go to step 12). If voltage reading is not greater than 5.2 volts, go to next step.
  10. Check voltage between ground and 5-volt reference circuit at VCM harness connector. If voltage reading is greater than 5.2 volts, go to next step. If voltage reading is not greater than 5.2 volts, go to step 17).
  11. Disconnect EGR harness connector. Check voltage on 5-volt reference circuit at VCM harness connector. If voltage reading is greater than 5.2 volts, go to step 16). If voltage reading is not greater than 5.2 volts, go to step 15).
  12. Repair short to voltage on the 5-volt reference circuit. After repairs, go to step 18).
  13. Check for open in sensor ground circuit. If circuit is open, go to next step. If circuit is okay, go to step 17).
  14. Repair as necessary. After repairs, go to step 18).
  15. Replace EGR valve. After replacing EGR, go to step 18).
  16. Repair short to voltage on 5-volt reference circuit. After repairs, go to step 18).
  17. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  18. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  19. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.

Check for and repair the following condition(s)

  1. Throttle plate sticking or excessive deposits on throttle plate or throttle bore.
  2. Check TP sensor harness connector ground circuit for open, and signal circuit for short to ground.
  3. TP sensor signal voltage should be less than 1.25 volt with throttle closed, and greater than 4.5 volts at wide open throttle.
  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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 ignition on. Using scan tool, compare ECT and IAT values. If values are close, go to next step. If values are not close, go to DTC P0117 diagnosis.
  3. Start engine. Using scan tool, monitor ECT value. If ECT value rises steadily to greater than 95°F (35°C) within 9 minutes, see DIAGNOSTIC AIDS. If ECT value does not rise steadily to greater than 95°F (35°C) within 9 minutes, go to next step.
  4. Check coolant level. If coolant level is low, diagnose cooling system. If coolant level is okay, go to next step.
  5. Compare actual coolant temperature with scan tool ECT value. If temperatures are close, repair cooling system as necessary. If temperatures are not close, go to next step.
  6. Replace ECT sensor. After replacing sensor, go to next step.
  7. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

Ensure thermostat is operating properly. 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.

Check for skewed ECT sensor. See ECT TEMPERATURE-TO-RESISTANCE VALUES table.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Start and allow engine to reach normal operating temperature. Apply parking brake. Place gear selector in Park or Neutral. Increase engine speed to 1200 RPM. Using scan tool, read HO2S voltage. If voltage is less than 0.086 volt, go to next step. If voltage is not less than 0.086 volt, go to step 4).
  3. Turn ignition off. Disconnect HO2S connector. Connect a jumper wire between HO2S harness connector ground circuit and chassis ground. Turn ignition on, engine off. If voltage is 0.35-0.55 volt, go to step 7). If voltage is not as specified, go to step 5).
  4. DTC is intermittent. Check if any additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  5. Check HO2S sensor harness connector signal circuit for short to ground. If sensor circuit is shorted, go to next step. If sensor circuit is okay, go to step 8).
  6. Repair circuit as necessary. After repairs, go to step 10).
  7. See DIAGNOSTIC AIDS. If a problem is found, go to step 10). If no problem is found, go to next step.
  8. Replace HO2S. After replacing sensor, go to step 10).
  9. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  10. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  11. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.

Using scan tool, observe LT FUEL TRIM values at different RPM. If conditions to set DTC 1031 exist, value should be about 158 or greater. Check for an intermittent short to ground in HO2S signal circuit. Never solder HO2S wires. Check for fuel contamination. Check for proper fuel pressure. Check for exhaust leaks.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Start and allow engine to reach normal operating temperature. Apply parking brake. Place gear selector in Park or Neutral. Increase engine speed to 1200 RPM. Using scan tool, read HO2S voltage. If voltage is greater than 0.976 volt, go to next step. If voltage is not greater than 0.976 volt, go to step 4).
  3. Turn ignition off. Disconnect HO2S harness connector. Turn ignition on, engine off. If scan tool data indicates that HO2S voltage is about 400 mV, go to step 6). If scan tool data indicates that HO2S voltage is not about 400 mV, go to step 5).
  4. DTC is intermittent. Check if any additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  5. Check for short to voltage in HO2S signal circuit. If circuit is shorted, go to step 8). If circuit is okay, go to step 7).
  6. Replace HO2S. After replacing sensor, go to step 8).
  7. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  8. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  9. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are present, diagnose affected DTCs. If no additional DTCs are present, system is okay.

Check for proper fuel pressure. Check for proper fuel injector operation. Check EVAP canister for fuel saturation. Check for leaking fuel pressure regulator diaphragm. Check for proper TP sensor operation. Check HO2S for silicon contamination (powdery white deposit). Using scan tool, check HO2S voltage. Voltage should be greater than one volt. Check HO2S voltage with connector disconnected. If voltage goes from greater than one volt to about 0.45 volt, replace HO2S. Never solder HO2S wires.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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 are set, diagnose affected DTCs. If no other HO2S DTCs are set, go to next step.
  3. Turn ignition on, engine off. Using scan tool, monitor HO2S voltage. If displayed voltage gradually change by 150 mV, go to step 8). If voltage does not gradually change by 150 mV, go to next step.
  4. Disconnect HO2S harness connector. Using test light connected to ground, probe HO2S harness connector terminal "D". If test light illuminates, go to next step. If test light does not illuminate, go to step 6).
  5. Connect test light between HO2S harness connector terminals "C" and "D". If test light illuminates, go to step 15). If test light does not illuminate, go to step 10).
  6. Check for open HO2S fuse. If fuse is open, go to step 11). If test light does not illuminate, go to next step.
  7. Check connections at HO2S. If problem is found, go to step 13). If connection is okay, go to step 12).
  8. Remove HO2S and inspect for contamination. If sensor is contaminated, go to step 14). If sensor is okay, go to next step.
  9. DTC is intermittent. Check is additional DTCs are present. Diagnose affected DTCs. If no additional DTCs are present, see DIAGNOSTIC AIDS.
  10. Repair open in HO2S ground circuit. After repairs, go to step 16).
  11. Repair short to ground in HO2S ignition feed circuit. After repairs, go to step 16).
  12. Repair open in HO2S ignition feed circuit. After repairs, go to step 16).
  13. Repair as necessary. After repairs, go to step 16).
  14. Repair source of HO2S contamination. After repairs, go to next step.
  15. Replace HO2S. After replacing sensor, go to next step.
  16. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  17. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

Check HO2S Heater operation. Never solder HO2S wires.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Warm engine to normal operating temperature. Apply parking brake. Place gear selector in Park or Neutral. Increase engine speed to greater than 1200 RPM for 2 minutes. Using scan tool, read LOOP MODE. If scan tool displays CLOSED LOOP, go to step 5). If scan tool does not display CLOSED LOOP, go to next step.
  3. Turn ignition off. Disconnect HO2S connector. Jumper HO2S signal and low circuits to ground. Turn ignition on, engine off. Using scan tool, check HO2S voltage display. If voltage is less than 200 mV, go to step 7). If voltage is not less than 200 mV, go to next step.
  4. Turn ignition off. Remove jumper wire. Reconnect HO2S connector. Disconnect VCM harness connector. Check voltage between VCM harness connector low circuit and battery voltage. If voltage reading is about 12 volts, go to step 7). If voltage reading is not about 12 volts, go to step 9).
  5. DTC is intermittent. check if any additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  6. Check for open in HO2S signal circuit. If circuit is open, go to step 11). If circuit is okay, go to step 8).
  7. Check HO2S sensor for faulty connection. If sensor connection is faulty, go to step 11). If connection is okay, go to step 10).
  8. Check VCM for faulty connection. If VCM connection is faulty, go to step 11). If connection is okay, go to step 12).
  9. Repair open HO2S ground circuit. After repairs, go to step 13).
  10. Replace HO2S. After replacing sensor, go to step 13).
  11. Repair circuit as necessary. After repairs, go to step 13).
  12. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  13. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  14. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

Check for faulty connections or damaged harness. Check for faulty HO2S heater. Observe scan tool while moving all related harness and connectors. A change in scan tool display indicates fault location.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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 one hour before proceeding with tests.
  2. Turn ignition off. Turn ignition on, engine off. Using scan tool, read HO2S voltage. If voltage gradually decreases by 150 mV, see DIAGNOSTIC AIDS. If voltage does not gradually decrease by 150 mV, go to next step.
  3. Check HO2S ignition feed circuit fuse. If fuse is open, go to step 12). If fuse is okay, go to next step.
  4. Turn ignition off. Disconnect HO2S harness connector. Connect a test light between a known-good chassis ground and ignition feed circuit at HO2S. If test light illuminates, go to next step. If test light does not illuminate, go to step 7).
  5. Connect test light between ignition feed and heater ground circuits at HO2S harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 8).
  6. Allow HO2S to cool down for 10 minutes. Using DVOM, check resistance between HO2S ignition feed circuit and heater ground circuit at HO2S pigtail. If resistance is 3-10 ohms, go to step 9). If resistance is not 3-10 ohms, go to step 11).
  7. Repair open in HO2S ignition feed circuit. After repairs, go to step 14).
  8. Repair open in HO2S heater ground circuit. After repairs, go to step 14).
  9. Check HO2S for faulty connection at harness connector terminals. If connection is faulty, go to step 14). If connection is okay, go to next step. 10 Turn ignition off. Disconnect VCM harness connector. Check resistance between HO2S signal and low circuits at harness connector. If resistance is greater than 5 ohms, go to step 13). If resistance is not greater than 5 ohms, go to next step.
  10. Replace HO2S. After replacing sensor, go to step 14).
  11. Repair short to ground in battery feed circuit. Replace fuse. After repairs, go to step 14).
  12. Repair open or poor connection HO2S signal or low circuit. After repairs, go to next step.
  13. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  14. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

Check for faulty connections or damaged harness. Never solder HO2S wires.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Warm engine to normal operating temperature. Apply parking brake. Place gear selector in Park or Neutral. Increase engine speed to 1200 RPM. Using scan tool, read HO2S voltage. If voltage is fixed at less than 0.86 volt, go to next step. If voltage is not fixed at less than 0.86 volt, go to step 4).
  3. Turn ignition off. Disconnect HO2S connector. Connect a jumper wire between HO2S harness connector ground (low) circuit and chassis ground. Turn ignition on, engine off. Using scan tool, read HO2S voltage. If voltage is 0.35-0.55 volt, go to step 7). If voltage is not 0.35-0.55 volt, go to step 5).
  4. DTC is intermittent. Check if any additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  5. Check HO2S sensor harness connector signal circuit for short to ground. If circuit is shorted, go to next step. If circuit is okay, go to step 9).
  6. Repair circuit as necessary. After repairs, go to step 10).
  7. See DIAGNOSTIC AIDS. If a problem is found, go to step 10). If no problem is found, go to next step.
  8. Replace HO2S sensor. After replacing sensor, go to step 10).
  9. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  10. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  11. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

Using scan tool, observe LT FUEL TRIM values at different RPM. If conditions to set DTC P1043 exist, value should be about 158 or greater. Check for an intermittent short to ground in HO2S signal circuit. Never solder HO2S wires. Check for fuel contamination. Check for proper fuel pressure. Check for exhaust leaks.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Warm engine to normal operating temperature. Apply parking brake. Place gear selector in Park or Neutral. Increase engine speed to 1200 RPM. Using scan tool, read HO2S voltage. If voltage is fixed at greater than 0.976 volt, go to next step. If voltage is not fixed at greater than 0.976, go to step 4).
  3. Turn ignition off. Disconnect HO2S connector. Using scan tool, check HO2S voltage. If voltage is about 400 mV, go to step 6). If voltage is not about 400 mV, go to step 5).
  4. DTC is intermittent. Check if any additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  5. Check for short to voltage in HO2S signal circuit. Repair as necessary. After repairs, go to step 8). If circuit is okay, go to step 7).
  6. Replace HO2S. After replacing sensor, go to step 8).
  7. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  8. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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 to step 2).
  9. Using scan tool, select Read and Record INFO, REVIEW INFO function. Check if any undiagnosed DTCs are displayed. Diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

Check for proper fuel pressure. Check for proper fuel injector operation. Check EVAP canister for fuel saturation. Check for leaking fuel pressure regulator diaphragm. Check for proper TP sensor operation. Check HO2S for silicone contamination (powdery white deposit). Using scan tool, check HO2S voltage. Voltage should be greater than one volt. Check HO2S voltage with connector disconnected. If voltage goes from greater than one volt to about 0.45 volt, replace HO2S. Never solder HO2S wires.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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 related DTCs are set, diagnose affected DTC. If no other HO2S related DTCs are set, go to next step.
  3. Turn ignition on, engine off. Using scan tool, monitor HO2S voltage. If voltage gradually change by 150 mV, go to step 8). If voltage does not gradually change by 150 mV, go to next step.
  4. Disconnect HO2S harness connector. Using a test light connected to ground, probe HO2S harness connector terminal "D". If test light illuminates, go to step 5). If test light does not illuminate, go to step 6).
  5. Connect test light between HO2S harness connector terminals "C" and "D". If test light illuminates, go to step 15). If test light does not illuminate, go to step 10).
  6. Check for open HO2S fuse. If fuse is open, go to step 11). If fuse is okay, go to next step.
  7. Check connection at HO2S. If connection is faulty, go to step 13). If connection is okay, go to step 12).
  8. Remove HO2S. Check for contamination. If sensor is contaminated, go to step 14). If sensor is not contaminated, go to next step.
  9. DTC is intermittent. Check if additional DTCs are present. If additional DTCs are present, diagnose affected DTCs. If no additional DTCs are present, see DIAGNOSTIC AIDS.
  10. Repair open in HO2S ground circuit. After repairs, go to step 16).
  11. Repair short to ground in HO2S ignition feed circuit. Replace fuse. After repairs, go to step 16).
  12. Repair open in HO2S ignition feed circuit. After repairs, go to step 16).
  13. Repair as necessary. After repairs, go to step 16).
  14. Repair source of contamination. After repairs, go to next step.
  15. Replace HO2S. After replacing sensor, go to next step.
  16. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  17. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

Check HO2S heater operation. Never solder HO2S wires.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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, engine off. Using scan tool, monitor HO2S voltage. If voltage gradually decreases by 150 mV, see DIAGNOSTIC AIDS. If voltage does not gradually decrease by 150 mV, go to next step.
  3. Check HO2S ignition feed fuse. If fuse is open, go to step 12). If fuse is okay, go to next step.
  4. Turn ignition off. Disconnect HO2S harness connector. Connect a test light between chassis ground and HO2S 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 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. Wait 10 minutes for sensor to cool down. Using DVOM, check resistance between HO2S pigtail ignition feed and heater ground circuits. If resistance is 3-10 ohms, go to step 9). If resistance is not 3-10 ohms, go to step 11).
  7. Repair open in HO2S ignition feed circuit. After repairs, go to step 14).
  8. Repair open in HO2S heater ground circuit. After repairs, go to step 14).
  9. Check poor connection at HO2S harness terminals. If faulty connection is found, go to step 14). If connection is okay, go to next step.
  10. Turn ignition off. Disconnect VCM harness connector. Using DVOM, check resistance between HO2S harness connector signal and low circuit. If resistance is greater than 5 ohms, go to step 13). If resistance is not greater than 5 ohms, go to next step.
  11. Replace HO2S. After replacing sensor, go to step 14).
  12. Repair short to ground in battery feed circuit. Replace fuse. After repairs, go to step 14).
  13. Repair open or poor connection in HO2S signal or low circuit. After repairs, go to next step. NOTE: Allow engine to cool down for about 30 minutes.
  14. Turn ignition on, engine off. Using scan tool, select DTC and CLEAR DTC INFO function. Monitor HO2S voltage. If voltage gradually decreases by 150 mV, go to next step. If voltage does not decrease by 150 mV, repeat step 3).
  15. Using scan tool, select Read and Record INFO, REVIEW INFO function. Check if any undiagnosed DTCs are displayed. Diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

Check for faulty connections or damaged harness. Never solder HO2S wires.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Warm engine to normal operating temperature. Apply parking brake. Place transmission in Park or Neutral. Increase engine speed to 1200 RPM. Using scan tool, monitor HO2S voltage. If voltage is less than 0.086 volt, go to next step. If voltage is not less than 0.086 volt, go to step 4).
  3. Turn ignition off. Disconnect HO2S harness connector. Connect a jumper wire between HO2S harness connector ground circuit and chassis ground. Turn ignition on, engine off. If voltage is 0.35-0.55 volt, go to step 7). If voltage is not 0.35-0.55 volt, go to step 5).
  4. DTC is intermittent. Check if any additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  5. Check HO2S sensor harness connector signal circuit for short to ground. If circuit is shorted, go to next step. If circuit is okay, go to step 9).
  6. Repair circuit as necessary. After repairs, go to step 10).
  7. See DIAGNOSTIC AIDS. If a problem is found, go to step 10). If no problem is found, go to next step.
  8. Replace HO2S. After replacing sensor, go to step 10).
  9. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  10. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  11. Using scan tool, select Read and Record INFO, REVIEW INFO function. Check if any undiagnosed DTCs are displayed. Diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

Using scan tool, observe LT FUEL TRIM values at different RPM. If conditions to set DTC 1051 exist, value should be about 158 or more. Check for an intermittent short to ground in HO2S signal circuit. Never solder HO2S wires. Check for fuel contamination. Check for proper fuel pressure. Check for exhaust leaks.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Warm engine to normal operating temperature. Apply parking brake. Place gear selector in Park or Neutral. Increase engine speed to 1200 RPM. Using scan tool, monitor HO2S voltage. If voltage is fixed at greater than 976 mV, go to next step. If voltage is not fixed at greater than 976 mV, go to step 4).
  3. Turn ignition off. Disconnect HO2S connector. Using scan tool, check HO2S voltage. If voltage is about 400 mV, go to step 6). If voltage is not about 400 mV, go to step 5).
  4. DTC is intermittent. Check if any additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  5. Check for short to voltage is HO2S signal circuit. If circuit is shorted, repair as necessary. After repairs, go to step 8). If circuit is okay, go to step 7).
  6. Replace HO2S. After replacing sensor, go to step 8).
  7. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  8. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  9. Using scan tool, select Read and Record INFO, REVIEW INFO function. Check if any undiagnosed DTCs are displayed. Diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

Check for proper fuel pressure. Check for proper fuel injector operation. Check EVAP canister for fuel saturation. Check for leaking fuel pressure regulator diaphragm. Check for proper TP sensor operation. Check HO2S for silicone contamination (powdery white deposit). Using scan tool, check HO2S voltage. Voltage should be more than one volt. Check HO2S voltage with connector disconnected. If voltage goes from more than one volt to about 0.45 volt, replace HO2S. Never solder HO2S wires.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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 related DTCs are set, diagnose affected DTCs. If no other HO2S related DTCs are set, go to next step.
  3. Turn ignition on, engine off. Using scan tool, monitor MAP sensor voltage. If voltage gradually changes by 150 mV, go to step 8). If voltage does not gradually change by 150 mV, go to next step.
  4. Disconnect HO2S harness connector. Using test light connected to ground, probe HO2S harness connector terminal "D". If test light illuminates, go to next step. If test light does not illuminate, go to step 6).
  5. Connect test light between HO2S harness connector terminals "C" and "D". If test light illuminates, go to step 15). If test light does not illuminate, go to step 10).
  6. Check for open HO2S fuse. If fuse is open, go to step 11). If fuse is okay, go to next step.
  7. Check HO2S connections. If a problem is found, go to step 13). If connections are okay, go to step 12).
  8. Remove HO2S. Inspect sensor for contamination. If sensor is contaminated, go to step 14). If sensor is not contaminated, go to next step.
  9. DTC is intermittent. Check if additional DTCs are present. Diagnose affected DTCs. If no additional DTCs are present, see DIAGNOSTIC AIDS.
  10. Repair open in HO2S ground circuit. After repairs, go to step 16).
  11. Repair short to ground in HO2S ignition feed circuit. Replace fuse. After repairs, go to step 16).
  12. Repair open in HO2S ignition feed circuit. After repairs, go to step 16).
  13. Repair as necessary. After repairs, go to step 16).
  14. Repair source of HO2S contamination. After repairs, go to next step.
  15. Replace HO2S. After replacing sensor, go to next step.
  16. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  17. Using scan tool, select Read and Record INFO, REVIEW INFO function. Check if any undiagnosed DTCs are displayed. Diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

Check HO2S Heater operation. Never solder HO2S wires.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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, check if any other HO2S related DTCs are set. If DTCs are set, diagnose affected DTCs. If not additional HO2S related DTCs are set, go to next step.
  3. Turn ignition on, engine off. Using scan tool, monitor HO2S voltage. If voltage is gradually changing by 150 mV, go to step 8). If voltage is not gradually changing by 150 mV, go to next step.
  4. Disconnect HO2S connector. Using a test light connected to ground, probe HO2S harness connector terminal "D". If test light illuminates, go to next step. If test light does not illuminate, go to step 6).
  5. Connect test light between HO2S harness connector terminals "C" and "D". If test light illuminates, go to step 15). If test light does not illuminate, go to step 10).
  6. Check for open HO2S fuse. If fuse is open, go to step 11). If fuse is okay, go to next step.
  7. Check connections at HO2S. If a problem is found, go to step 13). If connections are okay, go to step 12).
  8. Remove HO2S. Check sensor for contamination. If sensor is contaminated, go to step 14). If sensor is not contaminated, go to next step.
  9. DTC is intermittent. Check if any additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  10. Repair open in HO2S ground circuit. After repairs, go to step 16).
  11. Repair short to ground in HO2S ignition feed circuit. Replace fuse. After repairs, go to step 16).
  12. Repair open in HO2S ignition feed circuit. After repairs, go to step 16).
  13. Repair as necessary. After repairs, go to step 16).
  14. Repair source/cause of HO2S contamination. After repairs, go to next step.
  15. Replace HO2S. After replacing sensor, go to next step.
  16. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  17. Using scan tool, select Read and Record INFO, REVIEW INFO function. Check if any undiagnosed DTCs are displayed. Diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

Check for faulty connections or damaged harness. Check for faulty HO2S heater. Observe scan tool while moving all related harnesses and connectors. A change in scan tool display indicates fault location.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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, monitor HO2S voltage. If voltage gradually decreases by 150 mV, see DIAGNOSTIC AIDS. If voltage does not gradually decrease by 150 mV, go to next step.
  3. Check fuse to HO2S ignition feed. If fuse is open, go to step 12). If fuse is okay, go to next step.
  4. Turn ignition off. Disconnect HO2S harness connector. Connect a test light between a known-good ground and HO2S harness connector 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 ignition feed and heater ground circuits at HO2S harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 8).
  6. Allow H02S to cool for at least 10 minutes. Using DVOM, check resistance between HO2S ignition feed and heater ground circuit at sensor pigtail. If resistance is 3-10 ohms, go to step 9). If resistance is not 3-10 ohms, go to step 11).
  7. Repair open in HO2S ignition feed circuit. After repairs, go to step 14).
  8. Repair open in HO2S heater ground circuit. After repairs, go to step 14).
  9. Check for poor connection at HO2S harness connector. Repair as necessary. After repairs, go to step 14). If connections are okay, go to next step.
  10. Turn ignition off. Disconnect VCM harness connector. Using DVOM, check resistance between HO2S signal and low circuit. If resistance is greater than 5 ohms, go to step 13). If resistance is not greater than 5 ohms, go to next step.
  11. Replace HO2S. After replacing sensor, go to step 14).
  12. Repair short to ground in battery feed circuit. Repair as necessary. Replace fuse. After repairs, go to step 14).
  13. Repair open or poor connection in HO2S signal or low circuit. After repairs, go to next step. NOTE: If engine has been operating, allow engine to cool for about 30 minutes before proceeding with test.
  14. Turn ignition on, engine off. Using scan tool, select DTC, CLEAR INFO function. Monitor HO2S voltage. If voltage is gradually decreasing by 150 mV, go to next step. If voltage is not gradually decreasing by 150 mV, repeat step 3).
  15. Using scan tool, select Read and Record INFO, REVIEW INFO function. Check if any undiagnosed DTCs are displayed. Diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

Check for faulty connections or damaged harness. Never solder HO2S wires.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Check exhaust system for corrosion, loose or missing hardware. Ensure HO2S is installed securely, and connector and harness are not contacting exhaust manifold or ignition wires. Check vacuum hoses for splits, kinks and proper routing. Check throttle body, intake manifold, and EGR valve for vacuum leaks. Check IAC, if high or unsteady idle condition exists. Check crankcase ventilation valve, spring and "O" ring for proper installation. Check for fuel contamination. Check for good VCM and sensor grounds. If any of these items isolate or require repair, go to step 8). If all items are okay, go to next step.
  3. Turn ignition off. Connect fuel pressure gauge to fuel rail test fitting. Turn ignition on, engine off (fuel pump should run for about 2 seconds). Cycle ignition off and on until maximum pressure is obtained. Note fuel pressure while pump is running (pressure may vary slightly when pump stops). If pressure holds at 60-66 psi (4.2-4.6 kg/cm 2 ), go to next step. If pressure does not hold at 60-66 psi (kg/cm 2 , go to step 11).
  4. Warm engine to normal operating temperature. If fuel pressure drops 3-10 psi (0.2-0.7 kg/cm 2 ), go to next step. If fuel pressure does not drop 3-10 psi (0.2-0.7 kg/cm 2 ), go to step 11).
  5. Perform INJECTOR BALANCE TEST under FUEL SYSTEM in SYSTEM/COMPONENT TESTS - 4.3L article. If an injector problem is found, go to step 9). If injectors are okay, go to next step.
  6. Perform evap canister purge solenoid check. See FUEL EVAPORATION CONTROL under EMISSION SYSTEMS & SUB-SYSTEMS in SYSTEM/COMPONENT TESTS - 4.3L article. If a solenoid problem is found, go to next step. If solenoid is okay, see DIAGNOSTIC AIDS.
  7. Repair EVAP system. Operate vehicle in closed loop mode while using scan tool to read LT and ST FUEL TRIM values. LT FUEL TRIM value should decrease to less than 158, ST FUEL TRIM value should decrease to less than 180. If FUEL TRIM values are as specified, go to step 10). If values are not as specified, see DIAGNOSTIC AIDS.
  8. Repair items as necessary. Operate vehicle in closed loop mode while using scan tool to read LT and ST FUEL TRIM values. LT FUEL TRIM value should decrease to less than 158, ST FUEL TRIM value should decrease to less than 180. If FUEL TRIM values are as specified, go to step 10). If values are not as specified, go to step 3).
  9. Replace fuel injector(s) as necessary. Operate vehicle in closed loop mode while using scan tool to read LT and ST FUEL TRIM values. LT FUEL TRIM value should decrease to less than 158, ST FUEL TRIM value should decrease to less than 180. If FUEL TRIM values are as specified, go to next step. If values are not as specified, go to step 6).
  10. Lean condition does not exist. If driveability problem still exists, see TESTS W/O CODES - 4.3L article.
  11. Check fuel system. See BASIC FUEL SYSTEM CHECKS in BASIC TESTING - 4.3L article.
  12. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  13. Using scan tool, select Read and Record INFO, REVIEW INFO function. Check if any undiagnosed DTCs are displayed. Diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

If problem cannot be isolated, attempt driving vehicle under various load conditions while using scan tool to read LT and ST FUEL TRIM values. This may help isolate condition which set DTC P0171. If condition to set DTC cannot be duplicated, problem could have been caused by a cylinder misfire. See DTC P0300 .

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Check air intake duct for restrictions. Check for plugged air filter. Check IAC, if low or unsteady idle condition exists. Check throttle body for coking and IAC passages for blockage. Check fuel pressure regulator for proper operation. See BASIC FUEL SYSTEM CHECKS in BASIC TESTING - 4.3L article. Check TP sensor for loose or missing mounting bolts. Using scan tool, read TP sensor voltage while slowly opening throttle from closed (0.20-0.74 volt) to wide open (4 volts). A steady throttle movement from a stop should cause TP sensor voltage to increase smoothly as throttle is opened. If any of these items isolate or require repair, go to step 8). If all items are okay, go to next step.
  3. Turn ignition off. Connect a fuel pressure gauge to fuel rail test fitting. Turn ignition on, engine off (fuel pump should run for about 2 seconds). Cycle ignition off and on until maximum pressure is obtained. Note fuel pressure while pump is running (pressure may vary slightly when pump stops). If pressure holds at 60-66 psi (4.2-4.6 kg/cm 2 ), go to next step. If pressure is not as specified, go to step 11).
  4. Perform INJECTOR BALANCE TEST under FUEL SYSTEM in SYSTEM/COMPONENT TESTS - 4.3L article. If an injector problem is found, go to step 9). If injectors are okay, go to next step.
  5. Check HO2S for silicon contamination (powdery white) deposit. If contamination is evident, go to step 12). If contamination is not evident, go to next step.
  6. Perform EVAP CONTROL SYSTEM DIAGNOSIS. See BASIC TESTING - 4.3L article. If a problem is found, go to next step. If no problem is found, see DIAGNOSTIC AIDS.
  7. Repair EVAP system. Operate vehicle in closed-loop mode while using scan tool to read LT and ST FUEL TRIM values. If LT FUEL TRIM value increases to greater than 100 and ST FUEL TRIM value increases to greater than 94, go to step 10). If values are not as specified, see DIAGNOSTIC AIDS.
  8. Repair items as necessary. Operate vehicle in closed-loop mode while using scan tool to read LT and ST FUEL TRIM values. LT FUEL TRIM value should increase to greater than 100, ST FUEL TRIM value should increase to greater than 94. If FUEL TRIM values are as specified, go to step 10). If values are not as specified, repeat step 3).
  9. Replace fuel injector(s) as necessary. Operate vehicle in closed-loop mode while using scan tool to read LT and ST FUEL TRIM mode values. If LT value increases to greater than 100 and ST fuel value increases to greater than 94, go to next step. If values are not as specified, repeat step 5).
  10. Rich condition does not exist. If driveability problem still exists, see TESTS W/O CODES - 4.3L article.
  11. See BASIC FUEL SYSTEM CHECKS in BASIC TESTING - 4.3L article.
  12. Replace HO2S (bank 2 sensor 1). After replacing sensor, go to next step.
  13. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  14. Using scan tool, select Read and Record INFO, REVIEW INFO function. Check if any undiagnosed DTCs are displayed. Diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

If problem cannot be isolated, attempt driving vehicle under various load conditions while using scan tool to read LT and ST FUEL TRIM values. This may help isolate condition which set DTC P0172. If condition to set DTC cannot be duplicated, problem could have been caused by a cylinder misfire. See DTC P0300 .

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Check exhaust system for corrosion, loose or missing hardware. Ensure HO2S is installed securely, and connector and harness are not contacting exhaust manifold or ignition wires. Check vacuum hoses for splits, kinks and proper routing. Check throttle body, intake manifold, and EGR valve for vacuum leaks. Check IAC, if high or unsteady idle condition exists. Check crankcase ventilation valve, spring and "O" ring for proper installation. Check for fuel contamination. Check for good VCM and sensor grounds. If any of these items isolate or require repair, go to step 8). If all items are okay, go to next step.
  3. Turn ignition off. Connect fuel pressure gauge to fuel rail test fitting. Turn ignition on, engine off (fuel pump should run for about 2 seconds). Cycle ignition off and on until maximum pressure is obtained. Note fuel pressure while pump is running (pressure may vary slightly when pump stops). If pressure holds at 60-66 psi (4.2-4.6 kg/cm 2 ), go to next step. If pressure is not as 60-66 psi (4.2-4.6 kg/cm 2 ), go to step 11).
  4. Start and allow engine to idle. If pressure drops 3-10 psi (0.2-0.7 kg/cm 2 ), go to next step. If pressure does not drop 3-10 psi (0.2-0.7 kg/cm 2 ), go to step 11).
  5. Perform injector balance test. See SYSTEM/COMPONENT TESTS - 4.3L article. If an injector problem is found, go to step 9). If injectors are okay, go to next step.
  6. Perform canister purge solenoid check. See SYSTEM/COMPONENT TESTS - 4.3L article. If a solenoid problem is found, go to next step. If solenoid is okay, go to DIAGNOSTIC AIDS.
  7. Repair EVAP system. Operate vehicle in closed loop mode while using scan tool to read LT and ST fuel trim values. LT fuel trim value should decrease to less than 158, ST fuel trim value should decrease to less than 180. If fuel trim values are as specified, go to step 10). If values are not as specified, go to DIAGNOSTIC AIDS.
  8. Repair items as necessary. Operate vehicle in closed loop mode while using scan tool to read LT and ST fuel trim values. LT fuel trim value should decrease to less than 158, ST fuel trim value should decrease to less than 180. If fuel trim values are as specified, go to step 10). If values are not as specified, go to step 3).
  9. Replace fuel injector(s) as necessary. Operate vehicle in closed loop mode while using scan tool to read LT and ST fuel trim values. LT fuel trim value should decrease to less than 158, ST fuel trim value should decrease to less than 180. If fuel trim values are as specified, go to next step. If values are not as specified, go to step 6).
  10. Lean condition does not exist. If driveability problem still exists, see TESTS W/O CODES - 4.3L article.
  11. See BASIC FUEL SYSTEM CHECKS in BASIC TESTING - 4.3L article.
  12. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and this enter DTC. Operate vehicle within conditions required to set 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, go to step 2).
  13. Using scan tool, select Read and Record INFO, REVIEW INFO function. Check if any undiagnosed DTCs are displayed. Diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

If problem cannot be isolated, attempt driving vehicle under various load conditions while using scan tool to read LT and ST fuel trim values. This may help isolate condition which set DTC P0174. If condition to set DTC cannot be duplicated, problem could have been caused by a cylinder misfire. See DTC P0300 .

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Check air intake duct for restrictions. Check for plugged air filter. Check IAC, if low or unsteady idle condition exists. Check throttle body for coking and IAC passages for blockage. Check fuel pressure regulator for proper operation. See BASIC FUEL SYSTEM CHECKS in BASIC TESTING - 4.3L article. Check TP sensor for loose or missing mounting bolts. Using scan tool, read TP sensor voltage while slowly opening throttle from closed (0.20-0.74 volt) to wide open (4 volts). A steady throttle movement from a stop should cause TP sensor voltage to increase smoothly as throttle is opened. If any of these items isolate or require repair, go to step 8). If all items are okay, go to next step.
  3. Turn ignition off. Connect a fuel pressure gauge to fuel rail test fitting. Turn ignition on, engine off (fuel pump should run for about 2 seconds). Cycle ignition off and on until maximum pressure is obtained. Note fuel pressure while pump is running (pressure may vary slightly when pump stops). If pressure holds at 60-66 psi (4.2-4.6 kg/cm 2 ), go to next step. If pressure is not 60-66 psi (4.2-4.6 kg/cm 2 ), go to step 11).
  4. Perform injector balance test. See SYSTEM/COMPONENT TESTS - 4.3L article. If an injector problem is found, go to step 9). If injectors are okay, go to next step.
  5. Check HO2S for silicone contamination (powdery white) deposit. If contamination is evident, go to step 12). If contamination is not evident, go to next step.
  6. Perform canister purge solenoid check. See SYSTEM/COMPONENT TESTS - 4.3L article. If a solenoid problem is found, go to next step. If solenoid is okay, go to DIAGNOSTIC AIDS.
  7. Repair EVAP system. Operate vehicle in closed loop mode while using scan tool to read LT and ST fuel trim values. LT fuel trim value should increase to greater than 100, ST fuel trim value should increase to greater than 94. If fuel trim values are as specified, go to step 10). If values are not as specified, go to DIAGNOSTIC AIDS.
  8. Repair items as necessary. Operate vehicle in closed loop mode while using scan tool to read LT and ST fuel trim values. LT fuel trim value should increase to greater than 100, ST fuel trim value should increase to greater than 94. If fuel trim values are as specified, go to step 10). If values are not as specified, go to step 3).
  9. Replace fuel injector(s) as necessary. Operate vehicle in closed loop mode while using scan tool to read LT and ST fuel trim values. LT fuel trim value should increase to greater than 100, ST fuel trim value should increase to greater than 94. If fuel trim values are as specified, go to next step. If values are not as specified, go to step 5).
  10. Rich condition does not exist. If driveability problem still exists, see TESTS W/O CODES - 4.3L article.
  11. See BASIC FUEL SYSTEM CHECKS in BASIC TESTING - 4.3L article.
  12. Replace HO2S (bank 2 sensor 1). After replacing sensor, go to next step.
  13. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  14. Using scan tool, select Read and Record INFO, REVIEW INFO function. Check if any undiagnosed DTCs are displayed. Diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

If problem cannot be isolated, attempt driving vehicle under various load conditions while using scan tool to read LT and ST fuel trim values. This may help isolate condition which set DTC P0175. If condition to set DTC cannot be duplicated, problem could have been caused by a cylinder misfire. See DTC P0300 .

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Review FAILURE RECORDS data. If other DTCs are stored, diagnose affected DTCs. If no other DTCs are present, go to next step.
  3. Perform CKP System Variation Learn Procedure. See BASIC TESTING - 4.3L article. After performing CKP learn procedure, go to next step.
  4. Start and allow engine to idle. Using scan tool, monitor MAP sensor voltage. If voltage is greater than 4 volts, go to DTC P0108 for diagnosis. If voltage is not greater than 4 volts, go to next step.
  5. Turn ignition off, then turn ignition on, with engine off. Duplicate conditions required to set DTC. Using scan tool, read DTC PRESENT THIS IGNITION CYCLE. If the scan tool displays DTC P0300, PRESENT THIS IGN, go to next step. If the scan tool does not display DTC P0300, PRESENT THIS IGN, go to step 11).
  6. Using scan tool, review misfire index. If misfire index is increasing for more than one cylinder, see DIAGNOSTIC AIDS. If misfire index is not increasing for more than one cylinder, go to next step.
  7. Install a spark tester on No. 1 spark plug wire. Disconnect fuel injector harness at intake manifold. Crank engine and check for spark at tester. Repeat procedure for each spark plug wire. If spark is adequate on all wires, go to next step. If spark is not adequate, diagnose ignition system. See BASIC TESTING - 4.3L article.
  8. Remove and check spark plugs for wear, excessive gap, cracks or fouling. If spark plugs are okay, go to next step. If spark plugs are not okay, go to step 12).
  9. Perform cylinder compression test. If engine mechanical problem is found, repair as necessary. After repairs, go to step 14). If no mechanical problem is found, go to next step.
  10. Perform injector circuit test. See BASIC TESTING - 4.3L article. If fuel system is okay, go to next step. If fuel system is not okay, go to step 13).
  11. DTC is intermittent. Check if additional DTCs are present. Diagnose affected DTCs. If no additional DTCs are present, see DIAGNOSTIC AIDS.
  12. Replace spark plugs. After replacing spark plugs, go to step 14).
  13. Repair as necessary. After repairs, go to next step.
  14. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  15. Using scan tool, select Read and Record INFO, REVIEW INFO function. Check if any undiagnosed DTCs are displayed. Diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

A misfire could be caused by excessive vibration from sources other than engine. Check following items for possible cause of misfire: tire/wheel out of balance/round, uneven brake rotor or drum surface, or a rough road condition. Check plug wires for proper installation and operation. Check fuel level, condition and quality. If problem is intermittent, see TESTS W/O CODES - 4.3L article.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) , then go to next step.
  2. If engine knock can be heard, repair mechanical problem before proceeding. Install scan tool. Operate vehicle within the conditions for setting this DTC. Using scan tool, monitor SPECIFIC DTC for this DTC. If scan tool indicates that this DTC FAILED THIS IGN?, go to step 4). If scan tool does not indicate that this DTC FAILED THIS IGN?, go to next step.
  3. Turn ignition on, with engine off. Using scan tool, review and record FAILURE RECORDS data. Operate vehicle within FAILURE RECORDS conditions. Using scan tool, monitor SPECIFIC DTC for this DTC. If scan tool indicates that this DTC FAILED THIS IGN?, go to next step. If scan tool does not indicate that this DTC FAILED THIS IGN?, see DIAGNOSTIC AIDS.
  4. Check KS signal circuit for incorrect routing near secondary wires and repair as necessary. If a problem is found, go to step 8). If no problem is found, go to next step.
  5. Check if KS module is fully seated or incorrectly installed and repair as necessary. If a problem is found, go to step 8). If no problem is found, go to next step.
  6. Replace KS module. Operate vehicle within the conditions for setting this DTC. Using scan tool, monitor SPECIFIC DTC for this DTC. If scan tool indicates that this DTC FAILED THIS IGN?, go to next step. If scan tool does not indicate that this DTC FAILED THIS IGN?, go to step 8).
  7. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  8. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter this DTC. Operate vehicle within the 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).
  9. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.

Check for poor connections at VCM. Inspect KS module connector for backed-out terminals, broken locks, and improperly formed or damaged terminals. Check for damaged or improperly installed KS module. Check for bent pins, deformed terminals, or if KS module is fully seated. Check knock sensor torque specification. Specification should be 14 ft. lbs. (19 N.m). Checking FAIL RECORDS vehicle mileage data since diagnostic test last failed can be useful in determining how often condition causing DTC to set occurs. This may assist in diagnosis.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, 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, with engine off. Retrieve and record FAILED RECORDS data for DTC P0327. Operate vehicle within conditions required to set DTC. select DTC, SPECIFIC function and enter DTC P0327. If scan tool displays DTC P0327 FAILED THIS IGN, go to next step. If scan tool does not display DTC P0327 FAILED THIS IGN, see DIAGNOSTIC AIDS.
  4. Disconnect knock sensor harness connector. Using a DVOM, check voltage between KS signal circuit and ground. Voltage reading should be about 5 volts. If voltage is not as specified, go to step 8). If voltage is as specified, go to next step.
  5. Using DVOM, check resistance between knock sensor terminal and engine ground. Resistance should be about 100,000 ohms. If resistance is as specified, go to next step. If resistance is not as specified, go to step 12).
  6. Turn ignition off. Connect DVOM between knock sensor terminal and engine ground. Tap on engine while observing DVOM. If any signal is present, go to next step. If signal is not present, go to step 9).
  7. Check KS harness connector signal circuit for faulty terminal connection at KS. Repair as necessary. After repairs, go to step 14). If terminal connections are okay, go to step 10).
  8. Turn ignition off. Disconnect VCM harness connector. Turn ignition on and check KS signal circuit between VCM and KS harness connector for open, short to voltage or short to ground. Repair as necessary. After repairs, go to step 14). If circuit is okay, go to step 10).
  9. Replace knock sensor. After replacing sensor, go to step 14).
  10. Turn ignition off. Disconnect VCM harness connector. Check KS signal circuit for proper terminal connection at VCM. Repair or replace terminal as necessary. After repairs, go to step 14). If terminal is okay, go to next step.
  11. Ensure KS module is fully seated and installed properly. If a problem is found, repair as necessary. After repairs, go to step 14). If no problem is found, go to next step.
  12. Replace KS module. Operate vehicle within conditions required to set DTC. select DTC, SPECIFIC function and enter DTC P0327. 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 step 14).
  13. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  14. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter DTC P0327. Operate vehicle within conditions required to set DTC. If scan tool displays RAN AND PASSED, go to next step. If scan tool does not display RAN AND PASSED, return to step 2).
  15. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.

Check for faulty connection at VCM. Check KS and VCM connectors for damage. Ensure KS harness is not routed too close to high-voltage wires, such as spark plug cables, ignition coils or other high-voltage components. Insure KS is installed properly and ensure torque is to specification. Torque specification is 14 ft. lbs. (19 N.m).

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. If vehicle starts and runs, see DIAGNOSTIC AIDS. If vehicle does not start and run, go to next step.
  3. Disconnect CKP sensor harness connector. Using test light, probe ignition feed circuit of CKP sensor connector (engine side) to ground. Turn ignition on, engine off. If test light illuminates, go to next step. If test light does not illuminate, go to step 6).
  4. Connect test light between ignition feed circuit and sensor low circuit of CKP sensor connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 7).
  5. Turn ignition off. Install Gray jumpers from Connector Test Kit(J 35616-A) between engine harness connector and CKP sensor connector. Install DVOM set on duty cycle between CKP sensor 3X signal and low circuit terminals. Crank engine. If duty cycle is 40-60 percent, go to step 8). If duty cycle is not 40-60 percent, go to step 9).
  6. Repair open or short to ground in CKP sensor ignition feed circuit. After repairs, go to step 12).
  7. Check for open in CKP sensor low circuit. If CKP sensor low circuit is open, go to step 10). If circuit is okay, go to step 11).
  8. Check for open in CKP sensor 3X signal circuit or CKP sensor low circuit. If circuit is open, go to step 10). If circuit is okay, go to step 11).
  9. Replace CKP sensor. Ensure CKP sensor mounting surface is clean and free of debris. After repairs, go to step 12).
  10. Repair as necessary. After repairs, go to step 12).
  11. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  12. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  13. Using scan tool, select Read and Record INFO, REVIEW INFO function. Check if any undiagnosed DTCs are displayed. Diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

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

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Disconnect CKP sensor harness connector. Connect a test light between engine ground and signal circuit at CKP sensor. Turn ignition on, engine off. If test light illuminates, go to next step. If test light does not illuminate, go to step 8).
  3. Turn ignition off. Connect test light between battery voltage and ground circuit at CKP sensor. If test light illuminates, go to next step. If test light does not illuminate, go to step 7).
  4. Disconnect VCM harness connector. Connect test light between battery voltage and ignition feed circuit at CKP sensor. If test light illuminates, go to step 10). If test light does not illuminate, go to next step.
  5. Reconnect VCM harness connector. Install Gray jumpers from Connector Tester Kit (J 35616-A) between CKP sensor and CKP sensor harness connector. Start engine. Connect a DVOM (set to duty cycle) between CKP sensor signal and ground circuits. If duty cycle is less than 40 percent, go to step 11). If duty cycle is not less than 40 percent, go to next step.
  6. Check for faulty connection at CKP sensor. If a problem is found, go to step 12).
  7. Check for open in CKP sensor ground circuit. If circuit is open, go to step 12). If circuit is okay, go to step 9).
  8. Check for open or short to ground in CKP sensor signal circuit. If circuit is open, go to step 12).
  9. Check for faulty connection at VCM. If faulty connection is found, go to step 12). If connection is okay, go to step 13).
  10. Repair short to ground in CKP sensor signal circuit. After repairs, go to step 14).
  11. Replace CKP sensor. After replacing sensor, go to step 14).
  12. Repair circuit as necessary. After repairs, go to step 14).
  13. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  14. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  15. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.

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

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. If engine starts, go to step 4). If engine does not start, go to next step.
  3. Using scan tool, clear DTCs. Crank engine for 10 seconds and read DTCs. If DTC P0338 resets, go to next step. If DTC does not reset, go to NO START DIAGNOSIS in BASIC TESTING - 4.3L article.
  4. Start engine. Using scan tool, monitor engine speed (RPM). If RPM fluctuates up to twice desired RPM, go to step 14). If RPM does not fluctuate, go to next step.
  5. Turn engine off. Turn ignition on, with engine off. Disconnect CKP sensor harness connector. Connect a test light between engine ground and signal circuit at CKP sensor. If test light illuminates, go to next step. If test light does not illuminate, go to step 8).
  6. Connect test light between CKP sensor harness connector ground and signal circuits. If test light illuminates, go to next step. If test light does not illuminate, go to step 12).
  7. Turn ignition off. Install Gray jumpers from Connector Tester Kit (J 35616-A) between CKP sensor and CKP sensor harness connector. Using a DVOM, check voltage on CKP sensor harness connector signal circuit. If voltage is 2-3 volts, go to step 16). If voltage is not as specified, go to step 9).
  8. Turn ignition off. Disconnect VCM harness connector. Connect test light between battery voltage and ignition feed circuit at CKP sensor. If test light does not illuminate, go to step 15). If test light illuminates, go to step 11).
  9. Check for open in CKP sensor ground circuit. If circuit is open, go to step 17). If circuit is okay, go to next step.
  10. Check for short to ground in CKP sensor signal circuit. If circuit is shorted, go to step 17). If circuit is okay, go to step 13).
  11. Repair short to ground in CKP sensor ignition feed circuit. After repairs, go to step 19).
  12. Repair open CKP sensor ground circuit. After repairs, go to step 19).
  13. Check for faulty connection at CKP sensor. If faulty connection is found, go to step 17). If connection is okay, go to next step.
  14. Replace CKP sensor. After replacing sensor, go to step 19).
  15. Check for open in CKP sensor harness connector ignition feed circuit. If circuit is open, go to step 17). If circuit is okay, go to next step.
  16. Check for faulty connection at VCM. If connection is faulty, go to next step. If connection is okay, go to step 18).
  17. Repair circuit as necessary. After repairs, go to step 19).
  18. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  19. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  20. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.

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

Circuit Description

Crankshaft Position (CKP) sensor sends reference signal to VCM to indicate position of crankshaft and engine speed (RPM). VCM uses this information to determine ignition coil, fuel injector and ignition timing.

Conditions for setting DTC

  1. MAF at least 5 gm/s.
  2. Change in calculated engine speed is at least 1000 RPM.
  3. Calculated engine speed equals zero RPM and 4 or more CMP cycles have occurred for a period of 2-3 seconds.
  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. If engine starts and runs, see DIAGNOSTIC AIDS. If engine does not start and run, go to next step.
  3. Disconnect CKP sensor harness connector. Connect a test light between engine ground and ignition feed circuit at CKP sensor. Turn ignition on, engine off. If test light illuminates, go to next step. If test light does not illuminate, go to step 6).
  4. Connect test light between CKP sensor harness connector ground and ignition feed circuits. If test light illuminates, go to next step. If test light does not illuminate, go to step 7).
  5. Turn ignition off. Install Gray jumper wires from Connector Tester Kit (J 35616-A) between CKP sensor and sensor harness connector. Connect DVOM (set to duty cycle) between CKP sensor signal and ground circuits. Crank engine. If displayed duty cycle is 40-60 percent, go to step 8). If duty cycle is not 40-60 percent, go to step 10).
  6. Repair open or short to ground in CKP sensor ignition feed circuit. After repairs, go to step 13).
  7. Check CKP sensor harness ground circuit for an open. If circuit is open, go to step 11). If circuit is okay, go to step 9).
  8. Select DVOM AC volt scale. Crank engine. If voltage is greater than 10 volts, go to step 11). If voltage is not greater than 10 volts, go to next step.
  9. Check CKP sensor harness connector signal and ground circuits for an open. If circuit is open, go to step 11). If circuit is okay, go to step 12).
  10. Ensure CKP sensor mounting surface is clean and free of debris. Replace CKP sensor. After replacing sensor, go to step 13).
  11. Repair as necessary. After repairs, go to step 13).
  12. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  13. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this P0339. Operate vehicle within conditions required to set 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).
  14. Using scan tool, select Read and Record INFO, REVIEW INFO function. Check if any undiagnosed DTCs are displayed. Diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

Check for faulty connections or damaged harness. Observe scan tool while moving all related harnesses and connectors. A change in scan tool display indicates fault location. Inspect face of CKP sensor for metal shavings.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Start and operate engine at idle. Retrieve and record FREEZE FRAME and FAILED RECORDS data for this DTC. Continue to idle engine for one minute. Observe FREEZE FRAME, LAST TEST FAILED DTC. If this DTC P0340 FAILED is not displayed, go to step 8). If DTC P0340 FAILED is displayed, turn engine off. Restart engine. If MIL remains on, go to next step. If MIL does not remain on, go to step 8).
  3. Turn ignition on, with engine off. Disconnect CMP sensor harness connector. Connect a test light between engine ground and CKP sensor harness connector ignition feed circuit. If test light illuminates, go to next step. If test light does not illuminate, go to step 9).
  4. Connect test light between CMP sensor harness connector ground and ignition feed circuits. If test light illuminates, go to next step. If test light does not illuminate, go to step 11).
  5. Turn ignition off. Install Gray jumper wire from Connector Test Kit (J 35616-A) between CMP sensor and CMP sensor harness connector. Using a DVOM, check voltage between on CMP sensor signal circuit. If voltage is 5-7 volts, go to step 15). If voltage is not 5-7 volts, go to next step.
  6. Check CMP sensor harness connector signal circuit for open. If open is found, go to step 13). If open is not found, go to next step.
  7. Check CMP sensor harness connector signal circuit for short to voltage. If short is found, go to step 13). If short is not found, go to step 12).
  8. DTC is intermittent. Check if any additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  9. Check for open in CMP sensor harness connector ignition feed circuit. If circuit is open, go to step 13). If circuit is okay, go to next step.
  10. Repair short to ground in CMP sensor harness connector ignition feed circuit. After repairs, go to step 17).
  11. Repair open in CMP sensor harness connector ground circuit. After repairs, go to step 17).
  12. Check for faulty connection at CMP sensor. If connection is faulty, go to next step. If connection is okay, go to step 14).
  13. Repair circuit as necessary. After repairs, go to step 17).
  14. Replace CMP sensor. After replacing sensor, go to step 17).
  15. Check for faulty connection at VCM connector. If connection is faulty, go to step 13). If connection is okay, go to next step.
  16. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  17. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  18. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.

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

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Check for intermittent short to voltage or Electromagnetic Interference (EMI) on CMP sensor wires such as wires run alongside spark plug wires or high power transistors (like mobile radios operating nearby). If problem is found, go to next step. If no problem is found, go to step 4).
  3. Repair short to voltage or correct EMI interference. After repairs, go to next step.
  4. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  5. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.

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

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Start and warm engine to normal operating temperature. Operate engine at greater than 1500 RPM. Using scan tool, command EGR duty cycle through 25, 50, 75 and 100 percent positions. If engine runs rough as EGR is cycled, go to step 5). If engine does not run rough, go to next step.
  3. Turn engine off. Turn ignition on, engine off. Disconnect EGR valve harness connector. Connect a test light between EGR valve harness connector ignition feed and control circuits. If test light does not illuminate, go to next step. If test light illuminates, go to step 7).
  4. Start engine. Using scan tool, select MISCELLANEOUS TESTS, EGR CONTROL. With test light still connected, command EGR duty cycle increase to 100 percent. If test light illuminates as EGR is cycled, go to step 8). If test light does not illuminate, go to step 11).
  5. Remove EGR valve and inspect valve and passages for damage. Inspect valve pintle to ensure it is not sticking partially open. If a problem is found, go to step 10). If no problem is found, go to next step.
  6. DTC is intermittent. Check if additional DTCs are present. Diagnose affected DTCs. If no additional DTCs are present, see DIAGNOSTIC AIDS.
  7. Check for short to ground in EGR valve control circuit. If circuit is shorted, go to step 14). If circuit is okay, go to step 15).
  8. Check for restriction in EGR tube or passage. If restriction is found, go to step 10). If no restriction is found, go to next step.
  9. Check for faulty electrical connection at EGR valve. If faulty connection is found, go to step 14). If connection is okay, go to next step.
  10. Replace faulty EGR valve. After replacing EGR, go to step 16).
  11. Check for an open in EGR control circuit. If circuit is open, go to step 14). If circuit is okay, go to next step.
  12. Check for an open in EGR ignition feed circuit. If circuit is open, go to step 14). If circuit is okay, go to next step.
  13. Check for faulty connection at VCM. If connection is faulty, go to next step. If connection is okay, go to step 15).
  14. Repair circuit as necessary. After repairs, go to step 16).
  15. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  16. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set DTC. If scan tool indicates that this DTC RAN AND PASSED, go to next step. If scan tool does not display that this DTC RAN AND PASSED, repeat step 2).
  17. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.

Check for faulty connections or damaged harness. Inspect VCM 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.

If EGR valve shows signs of excessive heat, check exhaust system for blockage or plugged catalytic converter. Ensure fuel injectors are functioning properly and check engine oil for fuel contamination.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) , then go to next step.
  2. Turn ignition on, with engine off. Using scan tool, command EGR valve to 20, 50, 70, 100 percent. If actual EGR position follow the desired/commanded EGR position, go to step 5). If actual EGR position does not follow the desired/commanded EGR position, go to next step.
  3. Turn ignition off. Disconnect EGR harness connector. Turn ignition on, engine off. Using test light connected to battery voltage, probe EGR valve sensor ground circuit. If test light illuminates, go to next step. If test light does not illuminate, go to step 7).
  4. Connect test light to ground. Probe EGR feed control circuit at EGR harness connector. Using scan tool, command EGR valve to 20, 50, 70, 100 percent. If test light glows brighter, flash or maintain a steady dim glow as EGR is commanded, go to step 6). If test light does not glow as EGR is commanded, go to step 10).
  5. DTC is intermittent. Check for additional DTCs set. If DTCs are set, diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  6. Turn ignition on. Connect test light between battery voltage and EGR valve ground circuit. If test light illuminates, go to step 9). If test light does not illuminate, go to step 8).
  7. Check for open or poor connection in EGR valve feed control circuit. Repair as necessary. After repairs, go to step 22). If circuit or connection is okay, go to step 20).
  8. Check for open or poor connection in EGR valve feed control circuit. Repair as necessary. After repairs, go to step 22). If circuit or connection is okay, go to step 20).
  9. Connect test light between ground and EGR pintle position signal circuit. If test light illuminates, go to step 11). If test light does not illuminate, go to step 12).
  10. Using test light connected to ground, probe EGR valve feed control circuit without commanding EGR valve with scan tool. If test light illuminates, go to step 13). If test light does not illuminate, go to step 14).
  11. Check signal circuit for short to voltage. Repair as necessary. After repairs, go to step 22). If circuit is okay, go to step 20).
  12. Using DVOM, check voltage in 5-volt reference circuit. If voltage reading is about 5 volts, go to step 15). If voltage reading is not about 5 volts, go to step 16).
  13. Check EGR valve feed control circuit for short to voltage. Repair as necessary. After repairs, go to step 22). If circuit is okay, go to step 20).
  14. Connect test light between battery voltage and EGR valve feed control circuit. If test light illuminates, go to step 17). If test light does not illuminate, go to step 18).
  15. Check EGR sensor ground circuit for poor connection at EGR valve. Repair as necessary. After repairs, go to step 22). If connection is okay, go to step 19).
  16. Check 5-volt reference circuit for short to voltage. Repair as necessary. After repairs, go to step 22). If circuit is okay, go to step 20).
  17. Check EGR valve feed control circuit for short to ground. Repair as necessary. After repairs, go to step 22). If circuit is okay, go to step 20).
  18. Check EGR valve feed control circuit for open or poor connection at EGR valve harness connector. Repair as necessary. After repairs, go to step 22). If circuit is okay, go to step 20).
  19. Replace EGR valve. After replacing EGR valve, go to step 22).
  20. Check VCM harness connector for poor connection. Repair as necessary. After repairs, go to step 22). If connection is okay, go to next step.
  21. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  22. 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 did not indicate that this test ran and passed, repeat step 2).
  23. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, go to applicable DTC test. If no additional DTCs are set, system is okay.

Due to moisture in exhaust system, EGR valve may sometimes freeze and stick in colder weather. Problem may disappear after vehicle is brought into a warm shop for repairs. By using scan tool and watching actual EGR and desired EGR positions on a cold engine, fault can be easily verified. Check FREEZE FRAME data to determine if DTC set when vehicle was cold by viewing ECT.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) , then go to next step.
  2. Turn ignition on, with engine off. Using scan tool, command EGR valve to 20, 50, 70, 100 percent. If actual EGR position follow the desired/commanded EGR position, go to step 5). If actual EGR position does not follow the desired/commanded EGR position, go to next step.
  3. Turn ignition off. Disconnect EGR valve harness connector. Turn ignition on, engine off. Using DVOM, check voltage between ground and EGR 5-volt reference circuit at EGR valve. If voltage reading is less than 5 volts, go to step 8). If voltage reading is not less than 5 volts, go to next step.
  4. Using jumper wire, jumper EGR valve 5-volt reference circuit to signal circuit. If actual EGR position displayed is 100 percent, go to step 6). If actual EGR position displayed is not 100 percent, go to step 7).
  5. DTC is intermittent. Check if additional DTCs are set. If additional DTCs are set, diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  6. Check EGR valve 5-volt reference and signal circuits for poor connection or proper terminal connection. Repair as necessary. After repairs, go to step 15). If circuits or connections are okay, go to step 10).
  7. Connect test light between battery voltage and EGR valve signal circuit. If test light illuminates, go to step 11). If test light does not illuminate, go to step 12).
  8. Check for short to ground in EGR valve 5-volt reference circuit. Repair as necessary. After repairs, go to step 15). If circuit is okay, go to next step.
  9. Check for open in EGR valve 5-volt reference circuit. Repair as necessary. After repairs, go to step 15). If circuit is okay, go to step 13).
  10. Replace EGR valve. After replacing EGR valve, go to step 15).
  11. Check for short to ground in EGR valve signal circuit. Repair as necessary. After repairs, go to step 15). If circuit is okay, go to step 13).
  12. Check for open in EGR valve signal circuit. Repair as necessary. After repairs, go to step 15). If circuit is okay, go to next step.
  13. Check affected circuit for poor connection at VCM. Repair as necessary. After repairs, go to step 15). If connection is okay, go to next step.
  14. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  15. 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).
  16. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, go to applicable DTC test.

Due to moisture associated with exhaust systems, the EGR valve may freeze and stick in colder weather conditions at times. Using scan tool, watch actual EGR and desired EGR positions on a cold engine to verify fault. Check freeze frame data to determine if DTC was set when vehicle was cold by viewing ECT.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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 any other DTCs are present. Diagnose affected DTCs. If no other DTCs are set, go to next step.
  3. Check exhaust system for leaks, loose or missing hardware. Repair as necessary. After repairs, go to step 5 . If no problems were found, go to next step.
  4. Ensure correct OE three-way catalytic converter is installed. Check converter for dents, severe discoloration or holes. Ensure that oxygen sensors are properly installed and that wiring connections are properly retained and not damaged. Repair as necessary. After repairs, go to next step. If no problems were found, go to step 6 .
  5. Using scan tool, clear DTCs. Warm engine to normal operating temperature. Select DTC and SPECIFIC DTC function. Operate vehicle within conditions for setting this DTC and until scan tool indicates that this diagnostic test passed and ran. If scan tool indicates that this diagnostic passed, system is okay. If scan tool does not indicate that this diagnostic passed, go to next step.
  6. Correct engine misfire or mechanical fault before replacing catalytic converter. After replacing converter, retest system operation.

Difficulty may be experienced in simulating conditions to set DTC, especially in urban areas.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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 DTCs P0446, P0452 or P0453 is set. If any of these DTCs are set, diagnose affected DTC(s). If no other DTCs are set, go to next step.
  3. Turn ignition off. Remove fuel cap. Turn ignition on. Using scan tool, read FUEL TANK VACUUM. If scan tool displays zero in. H2O, go to next step. If scan tool does not display zero in. H2O, repair faulty fuel tank sensor circuit.
  4. Zero pressure and vacuum gauges on EVAP Pressure/Purge Diagnostic Station (J 41413). Reinstall fuel cap. Read and Record FAIL RECORDS data for DTC P0440. Clear DTCs. Using scan tool, command EVAP vent solenoid ON (closed). Connect EVAP pressure/purge diagnostic station to EVAP service port. Using diagnostic station, attempt to pressurize EVAP system to 5 in. H2O. If specified pressure is achieved, go to next step. If specified pressure is not achieved, go to step 6).
  5. Maintain EVAP system pressure at 5 in. H2O. Using scan tool, read FUEL TANK VACUUM. If scan tool displays 5 in. H2O, go to step 9). If scan tool does not display 5 in. H2O, go to step 8).
  6. Disconnect fuel tank vapor and EVAP purge lines from EVAP canister. Plug fuel tank vapor line fitting at EVAP canister. Connect a hand-held vacuum pump to EVAP purge line fitting at EVAP canister. Ensure EVAP vent solenoid is still commanded ON (closed). Attempt to apply 5 in. Hg to EVAP canister. If vacuum is maintained as specified, go to step 12). If vacuum cannot be maintained as specified, go to next step.
  7. Leave system connected as in previous step. Disconnect and plug vent valve hose. Using a hand-held vacuum pump, apply 5 in. Hg. If vacuum can be obtained and held, go to step 17). If vacuum cannot be obtained or held, go to step 11).
  8. Disconnect fuel tank vapor line from canister. Attempt to pressurize EVAP system using EVAP Pressure/Purge Diagnostic Station (J 41413). Start engine. Monitor pressure on diagnostic station gauge. If 5 in. H2O can be obtained and held, go to step 18). If 5 in. H2O cannot be obtained or held, go to step 15).
  9. Disconnect purge line from canister. Connect vacuum gauge to service port of diagnostic station. Start engine. Command EVAP solenoid valve to 100 percent. If vacuum reading is 12 in. Hg or greater, see DIAGNOSTIC AIDS. If vacuum reading is not 12 in. Hg or greater, go to next step.
  10. Disconnect purge line from purge solenoid valve. Start engine. Using scan tool, command EVAP purge solenoid purge solenoid ON (100 percent). If vacuum reading is 12 in. Hg or greater, go to step 14). If vacuum reading is not 12 in. Hg or greater, go to step 16).
  11. Check if vent hose is disconnected or damaged. Check EVAP canister for damage. Repair as necessary. After repairs, go to step 19). If no problem is found, go to step 18).
  12. Check for missing or faulty fuel filler cap. Check for disconnected, leaking or damaged fuel tank vapor line or EVAP purge line. Repair as necessary. After repairs, go to step 19). If no problem is found, go to next step.
  13. Using scan tool, command EVAP vent solenoid ON (closed). With EVAP pressure/purge diagnostic station connected to EVAP service port, continuously attempt to pressurize EVAP system to 15 in. H2O by leaving diagnostic station control knob in PRESSURIZE position. Using Ultrasonic Leak Detector (J 41413), locate and repair EVAP system leak. It may be necessary to lower fuel tank to check connections at top of tank. Repair leak as necessary. After repairs, go to step 19).
  14. Repair restriction in EVAP purge line. After repairs, go to step 19).
  15. Repair restriction in fuel tank vapor line. After repairs, go to step 19).
  16. Replace EVAP purge solenoid valve. After replacing solenoid valve, go to step 19).
  17. Replace EVAP vent valve. After replacing vent valve, go to step 19).
  18. Replace EVAP canister. After replacing canister, go to next step.
  19. Turn ignition on, engine off. Using scan tool, command EVAP vent solenoid ON (closed). Using diagnostic station, pressurize EVAP system to 15 in. H2O. Monitor EVAP diagnostic station pressure gauge. Turn diagnostic station rotary switch to HOLD position. If pressure decreases to less than 10 in. H2O within 2 minutes, system is okay. If pressure does not decrease to less than 10 in. H2O within 2 minutes, go to next step.
  20. Using scan tool, select DTC, CLEAR INFO function. Perform SERVICE BAY TEST for EVAP system. After performing test, go to next step.
  21. Using scan tool, select Read and Record INFO, REVIEW INFO function. Check if any undiagnosed DTCs are displayed. Diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

Check following items

  1. For missing or damaged "O" rings at EVAP canister fuel vapor and purge line fittings.
  2. For cracks or punctures in EVAP canister.
  3. For damaged or disconnected source vacuum line, EVAP purge line, vent hose or fuel tank vapor line.
  4. For faulty connections at VCM. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
  5. For damaged harness. Inspect wiring harness to EVAP vent solenoid, EVAP purge solenoid, and fuel tank pressure sensor for intermittent open or short.
  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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 P0446, P0452 or P0453 is set. If any of these DTCs are set, diagnose affected DTC. If DTCs are not set, go to next step.
  3. Turn ignition off. Remove fuel cap. Turn ignition on. Using scan tool, read FUEL TANK VACUUM. If scan tool displays zero in. H2O go to next step. If scan tool does not display zero in. H2O, repair faulty fuel tank sensor circuit.
  4. Zero pressure and vacuum gauges on EVAP Pressure/Purge Diagnostic Station (J-41413). Reinstall fuel cap. Read and Record FAIL RECORDS data for this DTC. Clear DTCs. Using scan tool, command EVAP vent valve on (closed). Connect EVAP Pressure/Purge Diagnostic Station (J 41413) to EVAP service port. Using diagnostic station, pressurize EVAP system to 15 in. H2O. Monitor pressure on diagnostic station gauge. If pressure decreases to less than 10 in. H2O, go to next step. If pressure does not decrease to less than 10 in. H2O, see DIAGNOSTIC AIDS.
  5. Disconnect fuel tank vapor and EVAP purge lines from EVAP canister. Plug fuel tank vapor line fitting at EVAP canister. Connect a hand vacuum pump to EVAP purge line fitting at EVAP canister. Ensure EVAP vent solenoid is still commanded ON (closed). Attempt to apply 5 in. Hg to EVAP canister. If vacuum is maintained as specified, go to step 10). If vacuum cannot be maintained as specified, go to next step.
  6. Leave system connected as in previous step. Disconnect and plug vent hose at vent valve. Using a hand-held vacuum pump, apply 5 in. Hg. If vacuum can be obtained and held, go to step 8). If vacuum cannot be obtained or held, go to next step.
  7. Check vent hose for leak. Repair as necessary. After repairs, go to step 12). If hose is okay, go to step 9).
  8. Replace EVAP vent valve. After replacing vent valve, go to step 12).
  9. Replace EVAP canister. After replacing canister, go to step 12).
  10. Check for missing or faulty fuel cap. Check for disconnected or leaking fuel tank vapor line. Check for disconnected or damaged EVAP purge line. Repair as necessary. After repairs, go to step 12). If no problem is found, go to next step.
  11. Using scan tool, command EVAP vent solenoid on (closed). With EVAP pressure/purge diagnostic station connected to EVAP service port, attempt to pressurize EVAP system to 15 in. H2O by leaving EVAP pressure/purge diagnostic station control knob in PRESSURIZE position. Using Ultrasonic Leak Detector (J 41413), locate and repair EVAP system leak. It may be necessary to lower fuel tank to check connections at top of tank. After repairs, go to next step.
  12. Turn ignition on, engine off. Using scan tool, command EVAP vent solenoid ON (closed). Using EVAP pressure/purge diagnostic station, pressurize EVAP system to 15 in. H2O. Monitor EVAP diagnostic station pressure gauge. Turn EVAP diagnostic station rotary switch to HOLD position. If pressure decreases to less than 10 in H2O within 2 minutes, repeat step 2). If pressure does not decrease as specified, go to next step.
  13. Using scan tool, select DTC, CLEAR INFO function. Using scan tool, perform SERVICE BAY TEST for EVAP system. After performing test, go to next step.
  14. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.

Check following items

  1. For missing or damaged "O" rings at EVAP canister fuel vapor and purge line fittings.
  2. For cracks or punctures in EVAP canister.
  3. For damaged or disconnected source vacuum line, EVAP purge line, vacuum line, EVAP purge line, vent hose or fuel tank vapor line.
  4. For faulty connections at VCM. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
  5. For damaged harness. Inspect wiring harness to EVAP vent solenoid, EVAP purge solenoid, and fuel tank pressure sensor for intermittent open or short.
  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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. Remove fuel cap. Turn ignition on. Using scan tool, read FUEL TANK PRESSURE. If scan tool displays zero in. H2O, go to next step. If scan tool does not display zero in. H2O, perform fuel tank sensor circuit diagnosis. See «FUEL TANK PRESSURE SENSOR DIAGNOSIS»(ref-131391-S27212864392001121900000) .
  3. Zero pressure and vacuum gauges on EVAP Pressure/Purge Diagnostic Station (J 41413). Reinstall fuel cap. Using scan tool, command EVAP vent solenoid ON (closed). Connect EVAP pressure/purge diagnostic station to EVAP service port. Using EVAP pressure/purge diagnostic station, pressurize EVAP system to 5 in. H2O. Using scan tool, read FUEL TANK VACUUM. If scan tool displays 5 in. H2O, go to next step. If scan tool does not display 5 in. H2O, repair faulty fuel tank sensor circuit.
  4. Maintain EVAP system pressure at 5 in. H2O. Using scan tool, command EVAP vent solenoid OFF (open). Monitor EVAP pressure/purge diagnostic station pressure gauge. If pressure decreases to zero in H2O within 5 seconds, see DIAGNOSTIC AIDS. If pressure does not decrease as specified, go to next step.
  5. Disconnect vent and fuel tank vapor hose from EVAP canister. Plug fuel tank vapor line fitting at EVAP canister. Switch EVAP pressure/purge diagnostic station rotary switch to RELEASE position. Connect a hand-held vacuum pump to EVAP purge line fitting on EVAP canister. Apply 5 in. Hg. If specified vacuum can be obtained, go to step 11). If specified vacuum cannot be obtained, go to next step.
  6. Check if vent hose is between EVAP canister and EVAP solenoid is kinked, pinched or blocked. If a problem is found, repair as necessary. After repairs, go to step 13). If no problem is found, go to next step.
  7. Turn ignition off. Disconnect vent valve harness connector. Turn ignition on, engine off. Using a test light connected to battery voltage, probe harness connector terminal "A". If test light illuminates, go to next step. If test light does not illuminate, go to step 10).
  8. Turn ignition off. Disconnect VCM harness connector. Connect test light between battery voltage and EVAP vent valve harness connector terminal "A". If test light does not illuminate, go to next step. If test light does not illuminate, go to step 12).
  9. Repair short to ground in EVAP vent valve control circuit. After repairs, go to step 13).
  10. Replace EVAP vent valve. After replacing valve, go to step 13).
  11. Replace EVAP canister. After replacing canister, go to step 13).
  12. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  13. Using scan tool, command EVAP vent solenoid ON (closed). With EVAP pressure/purge diagnostic station connected to EVAP service port, pressurize EVAP system to 5 in. H2O. Switch EVAP pressure/purge diagnostic station rotary switch to HOLD. Using scan tool, command EVAP vent solenoid OFF (open). If pressure decreases to zero in H2O within 5 seconds, go to next step. If pressure does not decrease as specified, repeat step 2).
  14. Using scan tool, select DTC and CLEAR DTC INFO functions. Clear DTCs. Perform EVAP SERVICE BAY TEST. After performing service bay test, go to next step.
  15. Check if additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, system is okay.

Check following items

  1. For missing or damaged "O" rings at EVAP canister fuel vapor and purge line fittings.
  2. For faulty connections at VCM. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
  3. For damaged harness. Inspect wiring harness to EVAP vent solenoid, EVAP purge solenoid, and fuel tank pressure sensor for intermittent open or short.
  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) , then go to next step.
  2. Turn ignition on, engine off. Using scan tool, monitor fuel tank pressure sensor reading. If fuel tank pressure sensor value is within -1.0 to 1.0 in. H2O, go to next step. If fuel tank pressure sensor value is not within -1.0 to 1.0 in. H2O, go to step 4).
  3. DTC is intermittent. Check for additional DTCs set. If additional DTCs are set, diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  4. Turn ignition off. Disconnect fuel tank pressure sensor harness connector. Turn ignition on, engine off. Using DVOM, check voltage between fuel tank pressure sensor harness connector 5-volt reference voltage and ground circuit. If voltage is about 5 volts, go to next step. If voltage is not about 5 volts, go to step 6).
  5. Turn ignition off. Using jumper wires, connect jumper between fuel tank pressure sensor 5-volt reference circuit at harness connector to sensor terminal. Connect jumper between sensor ground circuit at harness connector to sensor terminal. Turn ignition on, engine off. Using DVOM, check voltage between ground and sensor signal circuit. If voltage is 1.3-2.0 volts, go to step 13). If voltage is not 1.3-2.0 volts, go to step 11).
  6. Check for open fuel tank pressure sensor in 5-volt reference circuit. If circuit is open, go to step 15). If circuit is okay, go to next step.
  7. Check for short to ground in 5-volt reference circuit. If circuit is shorted, go to step 15). If circuit is okay, go to next step.
  8. Check 5-volt reference circuit for poor terminal contact at VCM. If problem is found, go to step 15). If terminal connection is okay, go to next step.
  9. Check for open in fuel tank pressure sensor ground circuit. If circuit is open, go to step 15). If circuit is okay, go to next step.
  10. Check sensor ground circuit for poor terminal connection at VCM. If problem is found, go to step 15). If terminal connection is okay, go to step 16).
  11. Check fuel pressure sensor signal for short to ground. If circuit is shorted, go to step 15). If circuit is okay, go to next step.
  12. Check fuel pressure sensor signal terminal connection at VCM. If problem is found, go to step 15). If terminal connection is okay, go to step 16).
  13. Check fuel tank pressure sensor for water intrusion, backed out terminal, improper terminal mating or poor terminal-to-wire connections. If problem is found, go to step 15). If sensor connections are okay, go to next step.
  14. Replace fuel tank pressure sensor. After replacing sensor, go to step 17).
  15. Repair circuit as necessary. After repairs, go to step 17).
  16. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, 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 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).
  18. 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 VCM or fuel tank pressure sensor.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) , then go to next step.
  2. Turn ignition on, engine off. Using scan tool, monitor fuel tank pressure sensor reading. If fuel tank pressure sensor value is within -1.0 to 1.0 in. H2O, go to next step. If fuel tank pressure sensor value is not within -1.0 to 1.0 in. H2O, go to step 4).
  3. DTC is intermittent. Check for additional DTCs set. If additional DTCs are set, diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  4. Turn ignition off. Disconnect fuel tank pressure sensor harness connector. Turn ignition on, engine off. Using DVOM, check voltage between fuel tank pressure sensor harness connector signal and ground circuits. If voltage is less than 0.22 volt, go to next step. If voltage is not less than 0.22 volt, go to step 6).
  5. Check voltage between 5-volt reference circuit and sensor ground circuit at fuel tank pressure sensor harness connector. If voltage is about 5 volts, go to step 9). If voltage is not about 5 volts, go to step 7).
  6. Check voltage between fuel tank pressure sensor signal and ground circuits. If voltage is greater than 0.5 volt, go to step 8). If voltage is not greater than 0.5 volt, go to step 10).
  7. Check for short to voltage in 5-volt reference circuit. If circuit is shorted, go to step 11). If circuit is okay, go to step 9).
  8. Check for short to voltage in fuel tank pressure sensor signal circuit. If circuit is shorted, go to step 11). If circuit is okay, go to step 12).
  9. Check fuel tank pressure sensor for water intrusion, backed out terminal, improper terminal mating or poor terminal-to-wire connections. If problem is found, go to step 11). If sensor connections are okay, go to step 12).
  10. Check terminal contact at VCM. If problem is found, go to next step. If terminal contact is okay, go to step 13).
  11. Repair circuit as necessary. After repairs, go to step 14).
  12. Replace fuel tank pressure sensor. After replacing sensor, go to step 14).
  13. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, 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).
  15. 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 VCM or fuel tank pressure sensor.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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, with engine off. Using scan tool, record fuel level sensor voltage. Change fuel level in fuel tank. Observe fuel level sensor voltage on scan tool. If fuel level sensor voltage changed on scan tool, go to next step. If fuel level sensor voltage did not change on scan tool, go to step 4).
  3. DTC is intermittent. Check if additional DTCs are set. diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  4. Turn ignition off. Locate and disconnect fuel level sensor harness connector in fuel tank. Turn ignition on, engine off. Using DVOM connected to ground, probe fuel level sensor signal circuit. If voltage reading is about 5 volts, go to step 6). If voltage reading is not about 5 volts, go to next step.
  5. Repair open or short to ground in fuel level signal circuit. After repairs, go to step 9).
  6. Check fuel level sensor for corrosion and proper mating at connector. Check for proper alignment in fuel tank. check for restricted/binding level float. If a problem is found, go to next step. If no problem is found, go to step 8).
  7. Repair as necessary. After repairs, go to step 9).
  8. Replace fuel level sender. After replacing sender, go to next step.
  9. Using scan tool, record fuel level sensor voltage. Change fuel level in fuel tank. If fuel level sensor voltage changes, go to next step. If fuel level sensor voltage does not change, repeat step 2).
  10. Using scan tool, display CAPTURE and REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

Check for poor connection or damaged harness. Inspect VCM harness connectors for backed-out terminals, improper mating, broken locks or poor wire-to-terminal connections.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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, with engine off. Using scan tool, observe fuel level sensor voltage reading. If voltage reading is less than 0.39 volt, go to step 4). If voltage reading is not less than 0.39 volt, go to next step.
  3. DTC is intermittent. Check if additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTICS AIDS.
  4. Turn ignition off. Disconnect fuel level sending unit harness connector at fuel tank. Turn ignition on, engine off. Using DVOM, check voltage between ground and fuel level signal circuit at harness connector. If voltage reading is about 5 volts, go to step 6). If voltage reading is not about 5 volts, go to next step.
  5. Check for short to ground in fuel level signal circuit. If circuit is shorted, go to step 7). If circuit is okay, go to step 9).
  6. Check fuel level sending unit for corrosion, faulty terminal connector, proper alignment to tank or for restricted/binding fuel level float. If problem is found, go to next step. If no problem is found, go to step 8).
  7. Repair as necessary. After repairs, go to step 10).
  8. Replace fuel level sending unit. After replacing sender, go to step 10).
  9. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  10. Using scan tool, select DTC and CLEAR INFO function. Warm engine to normal operating temperature. Select DTC and SPECIFIC DTC, then enter this DTC. 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).
  11. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.

Check for damaged harness or poor connection at VCM or fuel level sensor.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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, with engine off. Using scan tool, observe fuel level sensor voltage reading. If voltage reading is greater than 2.9 volts, go to step 4). If voltage reading is not greater than 2.9 volts, go to next step.
  3. DTC is intermittent. check if additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  4. Turn ignition off. Disconnect fuel tank level sensor connector at fuel tank. Using DVOM connected to ground, probe fuel level sensor signal circuit. If voltage reading is about 5 volts, go to step 6). If fuel voltage is not about 5, go to next step.
  5. Check for open in fuel level sensor input circuit. If a problem is found, go to step 10). If no problem is found, go to next step.
  6. Using test light connected to battery voltage, probe fuel level ground circuit. If test light illuminates, go to step 9). If test light does not illuminate, go to step 8).
  7. Check for short to voltage in fuel level signal circuit. If circuit is shorted, go to step 10). If circuit is okay, go to step 12).
  8. Check for open in fuel level ground circuit. If circuit is open, go to step 10). If circuit is okay, go to step 12).
  9. Check connector at fuel level sensor for corrosion or improper mating. If problem is found, go to next step. If connector is okay, go to step 11).
  10. Repair circuit as necessary. After repairs, go to step 13).
  11. Replace fuel level sender. After replacing sender, go to step 13).
  12. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  13. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  14. Using scan tool, select CAPTURE INFO, REVIEW INFO function. Check if any undiagnosed DTCs are displayed. Diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

Intermittent can be caused by poor connection, rubbed-through wire insulation, or a wire broken inside the insulation. Check connectors for backed-out terminals, improper mating, broken lock, damaged terminal or poor terminal to wire connection. If electrical interference is suspected, install additional ground wire from IPC to negative battery terminal.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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. Using Connector Test Adapter Kit (J 35616-A) and a DVOM set to AC 200 volt scale, backprobe across VSS harness connector signal and ground circuits. Raise and support vehicle. Start engine and place transmission in gear. If voltage is constant, go to step 5). If voltage is not constant, go to next step.
  3. If voltage varies, see DIAGNOSTIC AIDS. If voltage does not vary, go to next step.
  4. If scan tool displays NO VOLTAGE, go to step 11). If scan tool does not display NO VOLTAGE, go to step 12).
  5. With vehicle still raised, disconnect VSS connector. With engine running, place transmission in gear. Using a DVOM on 200-volt AC scale, check voltage across signal and ground circuits at VSS. If voltage varies with RPM, go to step 7). If voltage does not vary, go to next step.
  6. Replace VSS. After replacing sensor, go to step 12).
  7. Check for faulty connection at VCM and VSS. If faulty connection is found, go to step 9). If connections are okay, go to next step.
  8. Check for open or short in ground and signal circuits between VCM and VSS. If problem is found, go to step 10). If no problem is found, go to step 12).
  9. Repair connection as necessary. After repairs, go to step 12).
  10. Repair open or short as necessary. After repairs, go to step 12).
  11. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  12. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter DTC P0500. Operate vehicle within conditions required to set DTC. If scan tool displays RAN AND PASSED, go to next step. If scan tool does not display RAN AND PASSED, return to step 2).
  13. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.

Ensure VCM is properly calibrated for vehicle speedometer.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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. If no other DTCs are set, go to next step.
  3. If DTC P0506 is active in this ignition cycle, go to step 5). If DTC is not active in this ignition cycle, go to next step.
  4. DTC is intermittent. Check if additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  5. Repair engine mechanical problem. After repairs, go to next step.
  6. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  7. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

Ensure throttle stop screw has not been tampered with. Check for stuck IAC valve or throttle linkage. Reset IAC using scan tool MISC FUNCTIONS. Check if fuel system is running too rich or too lean. Inspect throttle body bore for foreign material.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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. If no other DTCs are set, go to next step.
  3. If DTC P0507 is active this ignition cycle, go to step 6). If DTC is not active this ignition cycle, go to next step.
  4. DTC is intermittent. Check if additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  5. Repair engine mechanical problem. After repairs, go to next step.
  6. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  7. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.

Ensure throttle stop screw has not been tampered with. Check for stuck IAC valve or throttle linkage. Reset IAC using scan tool MISC FUNCTIONS. Check if fuel system is running too rich or too lean. Inspect throttle body bore for foreign material.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) , then go to next step.
  2. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  3. 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).
  4. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, go to applicable DTC test.

Replace VCM even if DTC only exists as a history code.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) , then go to next step.
  2. Flash VCM with current software. If DTC is reset, go to next step. If DTC does not reset, go to step 5).
  3. Verify that test equipment used is operating properly and that all connections are clean and tight. Attempt to flash VCM again. If DTC resets, go to next step. If DTC does not reset, go to step 5).
  4. Replace VCM. Program replacement VCM using required equipment. After repair is completed, go to next step.
  5. 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).
  6. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, go to applicable DTC test.

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

DTC will set if data from the memory location does not match test data which was saved to memory.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) , then go to next step.
  2. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, go to applicable DTC test. If no additional DTCs are set, system is okay.

If battery was disconnected for any reason, DTC will set. VCM checks the memory at power-up. If the memory changes, it will reset. An intermittent loss of power or ground to VCM will also cause a reset.

VCM performs an internal self-test on its Random Access Memory (RAM) or read/write memory. If this self-test fails, this DTC will set. DTC will also set when if the data from the memory location does not match the test data which was just saved.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) , then go to next step.
  2. Replace VCM. Program replacement VCM using required equipment. After repair is completed, go to next step.
  3. 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).
  4. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, go to applicable DTC test.

VCM performs an internal self-test on its Random Access Memory (RAM) or read/write memory. If this self-test fails, this DTC will set. This DTC will also set if the checksum does not match the expected value.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) , then go to next step.
  2. Replace VCM. Program replacement VCM using required equipment. After repair is completed, go to next step.
  3. 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).
  4. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, go to applicable DTC test.
  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) , then go to next step.
  2. Turn ignition off. Install scan tool. Turn ignition on, with engine off. Using scan tool, display CLUTCH SWITCH parameter. Engage and disengage clutch several times. If scan tool display indicates change when clutch is engaged and disengaged, go to step 7). If scan tool display does not indicate change when clutch is engaged and disengaged, go to next step.
  3. Check if brake fuse is open. If fuse is open, go to step 8). If fuse is okay, go to next step.
  4. Turn ignition off. Disconnect clutch switch connector. Connect a jumper wire between ignition feed circuit and signal circuit of clutch switch connector. Turn ignition on, with engine off. Using scan tool, check if clutch switch is on. If scan tool indicates clutch switch is on, go to next step. If scan tool indicates clutch switch is off, go to step 6).
  5. Remove jumper wire from clutch switch connector. Using scan tool, check if clutch switch is off. If scan tool indicates clutch switch is off, go to step 11). If scan tool indicates clutch switch is on, go to step 9).
  6. Check for open in signal circuit. If a problem is found, go to step 12). If no problem is found, go to step 10).
  7. DTC is intermittent. Check if additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, see TESTS W/O CODES - 4.3L article.
  8. Check and repair conditions that caused fuse to blow. Replace fuse. After replacing fuse, go to step 14).
  9. Check for short to battery voltage in signal circuit. If a problem is found, go to step 12). If no problem is found, go to step 13).
  10. Check for poor connections at VCM connector. If a problem is found, go to step 12). If connections are okay, go to step 13).
  11. Replace clutch switch. After replacing switch, go to step 14).
  12. Repair as necessary. After repairs, go to step 14).
  13. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  14. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter this DTC. Operate vehicle within the 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).
  15. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTCs are displayed, go to applicable DTC test.
  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) , then go to next step.
  2. If engine idle is unstable, incorrect, or if manifold vacuum at idle is less than 15 in. Hg, repair as necessary. Install scan tool. With engine idling, monitor MAP sensor voltage using scan tool. If MAP sensor voltage is less than 4 volts, go to next step. If MAP sensor voltage is not less than 4 volts, go to step 4).
  3. Turn ignition off. Disconnect MAP sensor connector. Turn ignition on. Monitor MAP sensor voltage using scan tool. If MAP sensor voltage is less than one volt, go to step 5). If MAP sensor voltage is not less than one volt, go to step 9).
  4. DTC is intermittent. Check if additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  5. Using DVOM connected to ground, probe 5-volt reference circuit at MAP sensor connector. If voltage is greater than 5.2 volts, go to step 10). If voltage is not greater than 5.2 volts, go to next step.
  6. Using test light connected to battery voltage, probe MAP sensor connector ground circuit. If test light illuminates, go to step 7). If test light does not illuminate, go to step 14).
  7. Check for restriction in MAP sensor vacuum source. If a problem is found, go to step 15). If no problem is found, go to next step.
  8. Replace MAP sensor. After replacing sensor, go to step 19).
  9. Check for short to voltage in MAP signal circuit. If circuit is shorted, go to step 15). If circuit is okay, go to step 18).
  10. Turn ignition off. Disconnect VCM harness connector. Turn ignition on. Using DVOM, check voltage on VCM connector MAP sensor 5-volt reference circuit terminal and ground. If voltage is greater than 5.2 volts, go to next step. If voltage is not greater than 5.2 volts, go to step 13).
  11. Disconnect EGR electrical connector. Check voltage on VCM connector EGR sensor 5-volt reference circuit terminal. If voltage is greater than 5.2 volts, go to next step. If voltage is not greater than 5.2 volts, go to step 16).
  12. Repair short to voltage on 5-volt reference circuit. After repairs, go to step 19).
  13. Using DVOM connected to ground, check voltage on VCM connector TP sensor 5-volt reference circuit terminal. If voltage is greater than 5.2 volts, go to step 17). If voltage is not greater than 5.2 volts, go to step 18).
  14. Repair MAP ground circuit. After repairs, go to step 19).
  15. Repair as necessary. After repairs, go to step 19).
  16. Replace EGR valve. After replacing EGR valve, go to step 19).
  17. Repair short to voltage on the 5-volt reference circuit. After repairs, go to step 19).
  18. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  19. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter this DTC. Operate vehicle within the 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).
  20. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTCs are displayed, go to applicable DTC test.

An intermittent ground in MAP signal circuit or 5-volt reference circuit will result in DTC P1106 setting. With ignition on and engine off, manifold pressure is equal to atmospheric pressure with signal voltage high. VCM uses information as an indication of vehicle altitude.

To test accuracy of a suspect sensor, compare reading with a known-good vehicle. Reading should be 3.6-4.9 volts. If DTC is intermittent, see TESTS W/O CODES - 4.3L article. To check for intermittent connection, disconnect sensor from bracket and twist sensor by hand. Output changes greater than .1 volt indicates a poor connection or connector. If okay, replace sensor. Ensure electrical connection remains securely connected. If sensor is removed from intake manifold, sensor-to-manifold seal must be replaced.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Start and operate engine at idle. Using scan tool, read MAP sensor voltage. If voltage is less than 0.5 volt, go to next step. If voltage is not less than 0.5 volt, go to step 5).
  3. Turn ignition off. Disconnect MAP sensor harness connector. Connect a jumper wire between MAP sensor harness connector 5-volt reference and signal circuits. Turn ignition on. If voltage is greater than 4.7 volts, go to step 6). If voltage is not greater than 4.7 volts, go to next step.
  4. Turn ignition off. Disconnect jumper wire. Connect a test light between battery voltage and MAP sensor harness connector signal circuit. Turn ignition on. If voltage is greater than 4.7 volts, go to step 9). If voltage is not greater than 4.7 volts, go to step 7).
  5. DTC is intermittent. Check if any additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  6. Check for faulty connection at MAP sensor. If connection is faulty, go to step 12). If connection is okay, go to step 11).
  7. Check for open MAP sensor signal circuit. If sensor signal circuit is open, go to step 12). If circuit is okay, go to next step.
  8. Check MAP sensor signal circuit for short to ground. If circuit is shorted, go to step 12). If circuit is okay, go to step 13).
  9. Check for open in MAP sensor 5-volt reference circuit. If circuit is open, go to step 12). If circuit is okay, go to next step.
  10. Check MAP sensor 5-volt reference circuit for short to ground. If circuit is shorted, go to step 12). If circuit is okay, go to step 13).
  11. Replace faulty MAP sensor. After replacing sensor, go to step 14).
  12. Repair circuit as necessary. After repairs, go to step 14).
  13. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  14. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  15. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.

Check MAP sensor signal and 5-volt reference circuits for intermittent open condition.

With ignition on and engine off, MAP signal is equal to atmospheric pressure with signal voltage high. This information is used by VCM as an indication of altitude. Comparison of this reading with a known-good vehicle with same sensor is a way to check accuracy of suspect sensor. Reading should be within 0.4 volt.

Disconnect sensor from bracket and twist sensor by hand to check for intermittents. Output changes greater than 0.1 volt indicate a faulty sensor connection.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Start and operate engine at idle. Using scan tool, read IAT sensor voltage. If voltage is greater than 4.9 volts, go to next step. If voltage is not greater than 4.9 volts, go to step 6).
  3. Turn ignition off. Disconnect IAT sensor harness connector. Connect a jumper wire between IAT sensor harness connector 5-volt reference and ground circuits. Turn ignition on. If voltage is less than 0.82 volt, go to step 7). If voltage is not less than 0.82 volt, go to next step.
  4. Connect jumper wire between IAT sensor harness connector signal circuit and engine ground. If voltage is less than 0.82 volt, go to step 8). If voltage is 0.82 volt or greater, go to next step.
  5. If DTC P0123 is also set, go to DTC P0123 for diagnosis. If DTC P0123 is not set, go to step 9).
  6. DTC P1111 is intermittent. Check if any additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  7. Check for faulty connection at IAT sensor and at VCM. If faulty connection is found, go to step 10). If connections are okay, go to step 11).
  8. Check for open IAT sensor ground circuit. If circuit is open, go to step 10). If circuit is okay, go to step 12).
  9. Check for open IAT sensor signal circuit. If circuit is open, go to next step. If circuit is okay, go to step 12).
  10. Repair circuit as necessary. After repairs, go to step 13).
  11. Replace IAT sensor. After replacing sensor, go to step 13).
  12. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  13. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  14. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.

Check for faulty connections at IAT sensor and at VCM. Observe 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.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Start and operate engine at idle. Using scan tool, read IAT sensor voltage. If voltage is less than 0.82 volt, go to next step. If voltage is not less than 0.82 volt, go to step 5).
  3. Turn engine off. Turn ignition on. Disconnect IAT sensor harness connector. If voltage is greater than 4 volts, go to step 7). If voltage is not greater than 4 volts, go to next step.
  4. Turn ignition off. Using DVOM, check resistance across IAT sensor harness connector. If resistance is infinite, go to step 8). If resistance is not infinite, go to step 6).
  5. DTC is intermittent. Check if any additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  6. Repair short to ground in IAT sensor signal circuit. After repairs, go to step 9).
  7. Replace IAT sensor. After replacing sensor, go to step 9).
  8. Replace VCM. Replacement VCM requires special equipment for programming procedures. After replacing VCM, go to next step.
  9. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  10. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.

Check for faulty connections at IAT sensor and at VCM. Observe 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.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Start and operate engine at idle. Using scan tool, read ECT sensor voltage. If voltage is less than 0.82 volt, go to next step. If voltage is not less than 0.82 volt, go to step 5).
  3. Turn engine off. Disconnect ECT sensor harness connector. Turn ignition on. If voltage is greater than 4 volts, go to step 7). If voltage is not greater than 4 volts, go to next step.
  4. Turn ignition off. Using DVOM, check resistance across ECT sensor harness connector. If resistance is infinite, go to step 8). If resistance is not infinite, go to step 6).
  5. DTC is intermittent. Check if any additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  6. Repair short to ground in ECT sensor signal circuit. After repairs, go to step 9).
  7. Replace ECT sensor. After replacing sensor, go to step 9).
  8. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  9. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  10. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.

Check for short to ground in ECT sensor harness connector 5-volt reference circuit. Observe 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.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Start and operate engine at idle. Using scan tool, read ECT sensor voltage. If voltage is greater than 4.9 volts, go to next step. If voltage is not greater than 4.9 volts, go to step 5).
  3. Turn engine off. Turn ignition on. Disconnect ECT sensor harness connector. Connect a jumper wire across ECT sensor harness connector. If voltage is less than 0.82 volt, go to step 6). If voltage is not less than 0.82 volt, go to next step.
  4. Connect jumper wire between ECT sensor harness connector signal circuit and chassis ground. If voltage is less than 0.82 volt, go to step 7). If voltage is not less than 0.82 volt, go to step 8).
  5. DTC is intermittent. Check if any additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, go to DIAGNOSTIC AIDS.
  6. Inspect VCM and ECT sensor for proper connection. If a problem is found, go to step 10). If connections are okay, go to step 11).
  7. Check ECT sensor harness connector ground circuit for open between VCM and ECT sensor. If circuit is open, go to step 10). If circuit is okay, go to step 12).
  8. If DTC P0123 is also set, go to DTC P0123. If DTC P0123 is not set, go to next step.
  9. Check ECT sensor harness connector signal circuit for open between VCM and ECT sensor. If circuit is open, go to next step. If circuit is okay, go to step 12).
  10. Repair circuit as necessary. After repairs, go to step 13).
  11. Replace ECT sensor. After replacing sensor, go to step 13).
  12. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  13. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  14. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.

Check for faulty connections or open in 5-volt reference and ground circuits. Check for skewed ECT sensor. See ECT TEMPERATURE-TO-RESISTANCE VALUES table.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. With throttle closed, use scan tool to read TP signal voltage. If voltage is greater than 4.8 volts, go to next step. If voltage is not greater than 4.8 volts, go to step 6).
  3. Disconnect TP sensor harness connector. If voltage is less than 0.2 volt, go to next step. If voltage is not less than 0.2 volt, go to step 5).
  4. 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 9).
  5. If DTC P0108 is also set, go to DTC P0108 for diagnosis. If DTC is not set, go to step 8).
  6. DTC is intermittent. Check if any additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  7. Check for faulty connection at TP sensor. If connection is faulty, go to step 10). If connection is okay, go to step 11).
  8. Check for short to voltage in TP sensor harness connector signal circuit. If circuit is shorted, go to step 10). If circuit is okay, go to step 12).
  9. Check for open in TP sensor harness connector ground circuit. If circuit is open, go to next step.
  10. Repair circuit as necessary. After repairs, go to step 13).
  11. Replace TP sensor. After replacing sensor, go to step 13).
  12. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  13. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  14. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.

Check for and repair the following condition(s)

  1. Throttle plate sticking or excessive deposits on throttle plate or throttle bore.
  2. Check TP sensor harness connector ground circuit for open, and signal circuit for short to ground.
  3. TP sensor signal voltage should be less than 1.25 volt with throttle closed, and greater than 4.5 volts at wide open throttle.
  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. With throttle closed, use scan tool to read TP signal voltage. If voltage is less than 0.15 volt, go to next step. If voltage is not less than 0.15 volt, go to step 5).
  3. Disconnect TP sensor harness connector. Connect a jumper wire between TP sensor harness connector sensor signal and 5-volt reference circuits. If voltage is greater than 4 volts, go to step 13). If voltage is not greater than 4 volts, go to next step.
  4. Connect a test light between TP sensor harness connector signal circuit and battery voltage. If voltage is greater than 4 volts, go to step 6). If voltage is not greater than 4 volts, go to step 8).
  5. DTC is intermittent. Check if any additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  6. Check for open in TP sensor harness connector 5-volt reference circuit. If circuit is open, go to step 11). If circuit is okay, go to next step.
  7. Check for short to ground in TP sensor harness connector 5-volt reference circuit. If circuit is shorted, go to step 11). If circuit is okay, go to step 10).
  8. Check for open in TP sensor harness connector signal circuit. If circuit is open, go to step 11). If circuit is okay, go to next step.
  9. Check for short to ground in TP sensor harness connector signal circuit. If circuit is shorted, go to step 11). If circuit is okay, go to next step.
  10. Check for faulty connection at VCM. If connection is faulty, go to next step. If connection is okay, go to step 13).
  11. Repair circuit as necessary. After repairs, go to step 14).
  12. Replace TP sensor. After replacing sensor, go to step 14).
  13. Replace VCM. Program replacement VCM using required equipment. After replacing PCM, go to next step.
  14. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  15. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.

Check for and repair the following condition(s)

  1. Throttle plate sticking or excessive deposits on throttle plate or throttle bore.
  2. Check TP sensor harness connector 5-volt reference circuit for open or short to ground, and repair as necessary.
  3. TP signal voltage reading on scan tool should be less than 1.25 volt with throttle closed, and greater than 4.5 volts at wide open throttle.
  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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. If no other DTCs are set, go to next step.
  3. Warm engine to normal operating temperature. Increase engine speed to 1200-2000 RPM for 2 minutes. Using scan tool, read HO2S voltage. If voltage rapidly fluctuates from less than .30 volt to greater than .60 volt, go to next step. If voltage does not rapidly fluctuate from less than .30 volt to greater than .60 volt, go to step 5).
  4. Operate engine at 1200-2000 RPM. Using scan tool, check is engine is in closed-loop. If engine is in closed-loop mode, see DIAGNOSTIC AIDS. If engine is not in closed-loop mode, go to step 8).
  5. Operate engine at 1200-2000 RPM. Using scan tool, monitor HO2S voltage. If voltage stays within .30-.60 volt longer than it swings out of this range, go to step 8). If voltage swings out of the .30-.60 volts range, go to next step.
  6. Check VCM connector terminal contact at HO2S signal and low circuits. If terminal contact is faulty, go to step 10). If terminal contact is okay, go to next step.
  7. Check for poor connection at HO2S connector. If connection is faulty, go to step 10). If connection is okay, go to step 9).
  8. Check HO2S for possible silicon contamination, leading, incorrect gasket sealer, rich fuel mixture or antifreeze contamination. Repair problem as necessary. After repairs, go to next step. If no contamination was found, go to step 11).
  9. Replace HO2S. After replacing sensor, go to step 11).
  10. Repair or replace as necessary. After repairs, go to next step.
  11. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

Check HO2S heater operation.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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 any other DTCs are set, diagnose affected DTCs. If no other DTCs are set, go to next step.
  3. Warm engine to normal operating temperature. Set engine speed at 1200-2000 RPM for 2 minutes. Using scan tool, monitor HO2S voltage. If voltage rapidly switches from less than 0.3 volt to greater than 0.6 volt, go to next step. If voltage does not switch as specified, go to step 5).
  4. With engine speed still at 1200-2000 RPM, read LOOP MODE. If scan tool displays CLOSED LOOP, see DIAGNOSTIC AIDS. If scan tool does not display CLOSED LOOP, go to step 8).
  5. If voltage stays within 0.3-0.6 volt longer than it stays out of range, go to step 10). If voltage stays outside 0.3-0.6 volt longer than it stays within range, go to next step.
  6. Check for faulty connection at VCM HO2S (bank 1, sensor 1) terminals. If connection is faulty, go to step 10). If connection is okay, go to next step.
  7. Check for faulty connection at HO2S (bank 1, sensor 2). If connection is faulty, go to step 10). If connection is okay, go to next step.
  8. Replace HO2S (bank 1, sensor 1) and go to step 11).
  9. Check for HO2S contamination caused by leaded fuel, incorrect gasket sealer or over-rich operation. If problem is found, go to next step. If no problem is found, go to step 11).
  10. Repair or replace as necessary. After repairs, go to next step.
  11. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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. Using scan tool, select Read and Record INFO, REVIEW INFO function. Check if any undiagnosed DTCs are displayed. Diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

Never solder HO2S wires.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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 any other DTCs are set, diagnose affected DTCs. If no other DTCs are set, go to next step.
  3. Warm engine to normal operating temperature. Set engine speed at 1200-2000 RPM for 2 minutes. Using scan tool, monitor HO2S voltage. If voltage rapidly switches from less than 0.3 volt to greater than 0.6 volt, go to next step. If voltage does not switch as specified, go to step 5).
  4. With engine speed still at 1200-2000 RPM, read LOOP MODE. If scan tool displays CLOSED LOOP, see DIAGNOSTIC AIDS. If scan tool does not display CLOSED LOOP, go to step 8).
  5. If voltage stays within 0.3-0.6 volt longer than it stays out of range, go to step 10). If voltage stays outside 0.3-0.6 volt longer than it stays within range, go to next step.
  6. Check for faulty connection at VCM HO2S (bank 2, sensor 1) terminals. If connection is faulty, go to step 10). If connection is okay, go to next step.
  7. Check for faulty connection at HO2S (bank 2, sensor 1). If connection is faulty, go to step 10). If connection is okay, go to next step.
  8. Replace HO2S. After replacing sensor, go to step 11).
  9. Check for HO2S contamination caused by leaded fuel, incorrect gasket sealer or over-rich operation. If problem is found, go to next step. If no problem is found, go to step 11).
  10. Repair or replace as necessary. After repairs, go to next step.
  11. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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. Using scan tool, select Read and Record INFO, REVIEW INFO function. Check if any undiagnosed DTCs are displayed, diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

Never solder HO2S wires.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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 any other DTCs are set, diagnose affected DTCs. If no other DTCs are set, go to next step.
  3. Warm engine to normal operating temperature. Set engine speed at 1200-2000 RPM for 2 minutes. Using scan tool, monitor HO2S voltage. If voltage rapidly switches from less than 0.3 volt to greater than 0.6 volt, go to next step. If voltage does not switch as specified, go to step 5).
  4. With engine speed still at 1200-2000 RPM, read LOOP MODE. If scan tool displays CLOSED LOOP, see DIAGNOSTIC AIDS. If scan tool does not display CLOSED LOOP, go to step 8).
  5. If voltage stays within 0.3-0.6 volt longer than it stays out of range, go to step 10). If voltage stays outside 0.3-0.6 volt longer than it stays within range, go to next step.
  6. Check for faulty connection at VCM HO2S (bank 2, sensor 1) terminal. If connection is faulty, go to step 10). If connection is okay, go to next step.
  7. Check for faulty connection at HO2S (bank 2, sensor 1). If connection is faulty, go to step 10). If connection is okay, go to next step.
  8. Replace HO2S (bank 2, sensor 1). After replacing HO2S sensor, go to step 11).
  9. Check for HO2S contamination caused by leaded fuel, incorrect gasket sealer or over-rich operation. If problem is found, go to next step. If no problem is found, go to step 11).
  10. Repair or replace as necessary. After repairs, go to next step.
  11. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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. Using scan tool, select Read and Record INFO, REVIEW INFO function. Check if any undiagnosed DTCs are displayed. Diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

Never solder HO2S wires.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) , then go to next step.
  2. Perform CKP Variation Learning procedure as follows: Install scan tool. Apply parking brakes and block drive wheels. Close hood. Place transmission in Park (A/T) or Neutral (M/T). Warm engine to 150°F (65°C). Turn off all accessories. Apply service brakes for duration of procedure. Enable CKP SYSTEM VARIATION LEARN PROC. on scan tool. Slowly raise engine speed to 4000 RPM. Immediately release throttle when engine speed decreases. If scan tool shows CKP learn procedure is complete, go to step 5). If scan tool does not show CKP learn procedure is complete, go to next step.
  3. Attempt CKP learn procedure as many as 3 times. If scan tool indicates that learn procedure is complete, go to step 5). If scan tool does not indicate that learn procedure is complete, go to next step.
  4. Check CKP sensor and crankshaft reluctor wheel for damage. If problem is found, go to step 6). If no problem is found, see DIAGNOSTIC AIDS.
  5. Turn ignition off for 15 seconds, then go to step 7).
  6. Replace CKP sensor and/or reluctor wheel. After replacing components, go to next step.
  7. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter this DTC. Operate vehicle within the 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).
  8. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTCs are displayed, go to applicable DTC test.

If CKP learn procedure cannot be learned, check for a chipped or damaged reluctor wheel, incorrect CKP sensor alignment to reluctor wheel, excessive crankshaft runout, interference in signal circuit to CKP sensor or incorrect ratio of crankshaft to camshaft pulses.

If PCM receives an incorrect crankshaft to camshaft ratio, PCM will not allow scan tool to enable the learn procedure.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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. Using scan tool, read engine speed (RPM). If RPM fluctuates up to twice the desired RPM, go to next step. If RPM does not fluctuate up to twice the desired RPM, go to step 4).
  3. Replace CKP sensor. After replacing sensor, go to step 6).
  4. Check for proper distributor installation. If problem is found, go to next step. If no problem is found, go to step 6).
  5. Repair as necessary. After repairs, go to next step.
  6. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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, return to step 2).
  7. Using scan tool, select Read and Record INFO, REVIEW INFO function. Check if any undiagnosed DTCs are displayed. Diagnose affected DTCs. If no additional DTCs are displayed, system is okay.
  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Clear DTCs. Disconnect fuel injector connector. Crank engine 15 seconds. Read DTCs. If DTC P1351 sets, go to next step. If DTC does not set, see DIAGNOSTIC AIDS.
  3. Turn ignition off. Reconnect fuel injector connector. Disconnect ignition coil module connector. Using DVOM in AC scale, check voltage between engine ground and IC control circuit at ignition coil module, while cranking engine. If voltage is 1-4 volts, go to step 9). If voltage is not 1-4 volts, go to next step.
  4. Turn ignition off. Disconnect VCM harness connector. Check resistance of IC control circuit between VCM harness connector and ignition coil module. If resistance is less than 10 ohms, go to step 6). If resistance is not less than 10 ohms, go to next step.
  5. Repair open IC control circuit between VCM and ignition coil module. After repairs, go to step 16).
  6. Check for faulty connection at VCM. If connection is faulty, go to next step. If connection is okay, go to step 8).
  7. Repair faulty VCM connection. After repairs, go to step 16).
  8. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to step 16).
  9. Turn ignition off. Connect a test light between battery voltage and ignition coil module harness connector ground circuit. If test light illuminates, go to step 11). If test light does not illuminate, go to next step.
  10. Repair open ignition coil module ground circuit. After repairs, go to step 16).
  11. Turn ignition on. Connect test light between engine ground and ignition coil module harness connector ignition feed circuit, and then ignition coil module harness connector tachometer signal circuit. If test light illuminates on both circuits, go to step 13). If test light does not illuminate on both circuits, go to next step.
  12. Repair faulty circuit. After repairs, go to step 16).
  13. Check for faulty connection at ignition coil module. If connection is faulty, go to step 15). If connection is okay, go to next step.
  14. Replace ignition coil module. After replacing module, go to step 16).
  15. Repair faulty connection. After repairs, go to next step.
  16. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  17. Using scan tool, select Read and Record INFO, REVIEW INFO function. Check if any undiagnosed DTCs are displayed. Diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

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.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Clear DTCs. Disconnect fuel injector connector. Crank engine 15 seconds. Read DTCs. If DTC P1361 sets, go to next step. If DTC does not set, see DIAGNOSTIC AIDS.
  3. Turn ignition off. Reconnect fuel injector connector. Disconnect ignition coil module connector. Using DVOM AC scale, check voltage between engine ground and IC control circuit at ignition coil module, while cranking engine. If voltage is 1-4 volts, go to step 9). If voltage is not 1-4 volts, go to next step.
  4. Turn ignition off. Disconnect VCM harness connector. Connect a test light between battery voltage and ignition coil module harness connector IC control circuit. If test light illuminates, go to next step. If test light does not illuminate, go to step 6).
  5. Repair short to voltage in IC control circuit. After repairs, go to step 14).
  6. Connect test light between engine ground and IC control circuit at VCM. If test light illuminates, go to next step. If test light does not illuminate, go to step 8).
  7. Repair short to voltage in IC control circuit. After repairs, go to step 14).
  8. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to step 14).
  9. Turn ignition off. Connect a test light between battery voltage and ignition coil module harness connector ground circuit. If test light illuminates, go to step 11). If test light does not illuminate, go to next step.
  10. Repair open ignition coil module ground circuit. After repairs, go to step 14).
  11. Check for faulty connection at ignition coil module. If connection is faulty, go to step 13). If connection is okay, go to next step.
  12. Replace ignition coil module. After replacing module, go to step 14).
  13. Repair faulty connection. After repairs, go to next step.
  14. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  15. Using scan tool, select Read and Record INFO, REVIEW INFO function. Check if any undiagnosed DTCs are displayed. Diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

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.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Disconnect VCM and Electronic Brake Control Module (EBCM) harness connectors. Check for open in serial data circuit between EBCM and VCM. If circuit is open, go to next step. If circuit is okay, perform ABS system diagnosis. See ANTI-LOCK BRAKE SYSTEM article in BRAKES section.
  3. Repair as necessary. After repairs, go to next step.
  4. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  5. Using scan tool, select Read and Record INFO, REVIEW INFO function. Check if any undiagnosed DTCs are displayed. Diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

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.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. Disconnect VCM and Electronic Brake Control Module (EBCM) harness connectors. Check for open in serial data circuit between EBCM and VCM. If circuit is open, go to next step. If circuit is okay, perform ABS system diagnosis. See ANTI-LOCK BRAKE SYSTEM article in BRAKES section.
  3. Repair as necessary. After repairs, go to next step.
  4. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  5. Using scan tool, select Read and Record INFO, REVIEW INFO function. Check if any undiagnosed DTCs are displayed. Diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

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.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) , then go to next step.
  2. Turn ignition on, engine off. Using scan tool, command EGR valve to 20, 50, 70 and 100 percent. If actual EGR position follows commanded EGR position, go to next step. If actual EGR position does not follow commanded EGR position, go to step 4).
  3. DTC is intermittent. Check if additional DTCs are set. If additional DTCs are set, diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  4. Disconnect EGR harness connector. If actual EGR position is about zero percent, go to step 6). If actual EGR position is not about zero percent, go to next step.
  5. Check EGR valve signal circuit for short to voltage. Repair as necessary. After repairs, go to step 16). If circuit is okay, go to step 14).
  6. Using DVOM, check voltage between ground and EGR 5-volt reference circuit terminal at harness connector. If voltage reading is about 5 volts, go to next step. If voltage reading is not about 5 volts, go to step 8).
  7. Using test light connected to ground, probe test light to EGR valve feed control circuit terminal at harness connector. If test light illuminates, go to step 9). If test light does not illuminate, go to step 10).
  8. Check EGR 5-volt reference circuit for short to voltage. Repair as necessary. After repairs, go to step 16). If circuit is okay, go to step 14).
  9. Check EGR feed circuit for short to voltage. Repair as necessary. After repairs, go to step 16). If circuit is okay, go to step 14).
  10. Using test light connected to battery voltage, probe EGR valve ground circuit. If test light illuminates, go to next step. If test light does not illuminate, go to step 12).
  11. Check EGR valve ground circuit terminal for poor connection at EGR harness connector. Repair as necessary. After repairs, go to step 16). If connection is okay, go to step 13).
  12. Check for open EGR valve ground circuit. Repair as necessary. After repairs, go to step 16). If circuit is okay, go to step 14).
  13. Replace EGR valve. After replacing EGR valve, go to step 16).
  14. Check for poor connection at VCM harness connector. Repair as necessary. After repairs, go to step 16). If VCM harness connector is okay, go to next step.
  15. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  16. 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).
  17. If any other DTCs are set, diagnose DTCs as necessary. If no other DTCs are set, no problem is indicated at this time. See DIAGNOSTIC AIDS.

Moisture in exhaust system may cause EGR valve to freeze or stick in colder weather. After vehicle is brought into a warm shop for repairs, EGR valve warms and the problem goes away. By watching ACTUAL EGR POSITION and DESIRED EGR POSITION on a cold vehicle with a scan tool. View FREEZE FRAME data to determine if DTC set when vehicle was cold by viewing ENGINE COOLANT TEMPERATURE and INTAKE AIR TEMPERATURE.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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. Connect Enhanced EVAP Pressure Diagnostic Station (J-41413) to EVAP service port. Turn diagnostic station rotary switch to PURGE position. Start engine. Monitor vacuum on diagnostic station gauge. If vacuum is greater than -15 in. H2O and steady, go to next step. If vacuum is not greater than -15 in. H2O, see DIAGNOSTIC AIDS.
  3. Turn ignition off. Disconnect EVAP purge solenoid harness connector. Turn ignition on, engine off. Using a test light connected to battery voltage, probe EVAP solenoid harness connector terminal "B". If test light illuminates, go to next step. If test light does not illuminate, go to step 6).
  4. Turn ignition off. Disconnect VCM harness connector. Turn ignition on, engine off. Connect test light between battery voltage and EVAP purge solenoid connector terminal "B". If test light illuminates, go to next step. If test light does not illuminate, go to step 7).
  5. Repair short to ground in EVAP canister purge valve driver circuit. After repairs, go to step 8).
  6. Replace EVAP purge solenoid. After replacing solenoid, go to step 8).
  7. Replace VCM. Program replacement PCM using required equipment. After replacing VCM, go to next step.
  8. Using scan tool, select DTC and CLEAR DTC INFO function. Perform SERVICE BAY TEST for EVAP. After performing service bay test, go to next step.
  9. Using scan tool, select FREEZE FRAME and FAILURE RECORDS function. If any DTCs are present, diagnose affected DTCs. If no additional DTCs are present, system is okay.

Check vacuum hoses for damage. 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.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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. Connect IAC driver to IAC valve. Set parking brake, brake drive wheels and turn A/C off. Start and operate engine at idle in Park (A/T) or Neutral (M/T). Using scan tool, read engine speed (RPM). Using IAC driver, extend and retract IAC valve. If engine RPM decreases and increases as IAC valve is cycled, go to next step. If engine RPM does not change, go to step 4).
  3. If engine speed changes smoothly between 700-1500 RPM, go to step 5). If RPM does not change smoothly, go to next step.
  4. Check IAC valve passage. If passage is not okay, clean passage and go to step 12). If passage is okay, replace IAC valve. Disconnect negative battery cable for 10 seconds, then reconnect cable. Turn ignition on, engine off for 5 seconds. Turn ignition off for at least 10 seconds and go to step 12).
  5. Install IAC Node Light (J37027-A) in VCM harness. Cycle IAC driver and note lights. Both lights should cycle Green and Red, but not OFF as RPM changes from 700-1500 RPM. If lights flash as specified, go to step 8). If lights do not flash as specified, go to next step.
  6. Check for faulty connector terminal contacts, open circuits, short to ground or voltage, faulty VCM connection. If problem is found, go to next step. If no problem is found, go to step 11).
  7. Repair connection, terminal contact or circuit as necessary. After repairs, go to step 12).
  8. Using other connector on IAC driver pigtail, check resistance across IAC valve coils. Check resistance of IAC coil "B" HI and LO circuits. Check resistance of coil "A" HI and LO circuits. If resistance on both coils is 40-80 ohms, go to next step. If resistance is not as specified on both coils, go to step 10).
  9. Check resistance between coil "B" HI circuit and coil "A" LO circuit. Check resistance between coil "B" LO circuit and coil "A" HI circuit. Resistance should be infinite. If resistance is as specified between both coils, see DIAGNOSTIC AIDS. If resistance is not as specified, go to next step.
  10. Replace IAC valve. Disconnect negative battery cable for 10 seconds, then reconnect cable. Turn ignition on, engine off for 5 seconds. Turn ignition off for at least 10 seconds. After repairs, go to step 12).
  11. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  12. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set DTC. If scan tool displays RAN AND PASSED, go to next step. If scan tool does not display RAN AND PASSED, return to step 2).
  13. Using scan tool, select Read and Record INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, diagnose affected DTCs. If no DTCs are displayed, system is okay.

Check for stopped IAC valve, tampered throttle stop screw, and damaged throttle or linkage. Check for fuel system running too rich or too lean. Check throttle body bore for foreign material. Reset IAC using scan tool.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) . Retrieve 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. Connect IAC driver to IAC valve. Set parking brake, brake drive wheels and turn A/C off. Start and operate engine at idle in Park (A/T) or Neutral (M/T). Using scan tool, read engine speed (RPM). Using IAC driver, extend and retract IAC valve. If engine RPM decreases and increases as IAC valve is cycled, go to next step. If engine RPM does not change, go to step 4).
  3. If engine speed changes smoothly between 700-1500 RPM, go to step 5). If RPM does not change smoothly, go to next step.
  4. Check IAC valve passage. If passage is not okay, clean passage and go to step 12). If passage is okay, replace IAC valve. Disconnect negative battery cable for 10 seconds, then reconnect cable. Turn ignition on, engine off for 5 seconds. Turn ignition off for at least 10 seconds and go to step 12).
  5. Install IAC Node Light (J 37027-A) in VCM harness. Cycle IAC driver and note lights. Both lights should cycle Green and Red, but not OFF as RPM changes from 700-1500 RPM. If lights cycle as specified, go to step 8). If lights do not cycle as specified, go to next step.
  6. Check for faulty connector terminal contacts, open circuits, short to ground or voltage, faulty VCM connection. If problem is found, go to next step. If no problem is found, go to step 11).
  7. Repair connection, terminal contact or circuit as necessary. After repairs, go to step 12).
  8. Using other connector on IAC driver pigtail, check resistance across IAC valve coils. Check resistance between IAC coil "B" ground and signal circuits. Check resistance across coil "A" ground and signal circuits. If resistance on both coils is 40-80 ohms, go to next step. If resistance is not as specified on both coils, go to step 10).
  9. Check resistance between coil "B" signal circuit and coil "A" ground circuit. Check resistance between coil "B" ground circuit and coil "A" signal circuit. Resistance should be infinite. If resistance is as specified between both coils, see DIAGNOSTIC AIDS. If resistance is not as specified, go to next step.
  10. Replace IAC valve. Disconnect negative battery cable for 10 seconds, then reconnect cable. Turn ignition on, engine off for 5 seconds. Turn ignition off for at least 10 seconds. After repairs, go to step 12).
  11. Replace VCM. Program replacement VCM using required equipment. After replacing VCM, go to next step.
  12. Using scan tool, select DTC, CLEAR INFO function. Start engine and allow it to reach operating temperature. Using scan tool, select DTC, SPECIFIC function and enter this DTC. Operate vehicle within conditions required to set 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).
  13. Using scan tool, select Read and Record INFO, REVIEW INFO function. Check if any undiagnosed DTCs are displayed. Diagnose affected DTCs. If no additional DTCs are displayed, system is okay.

Check for stopped IAC valve, tampered throttle stop screw, and damaged throttle or linkage. Check for fuel system running too rich or too lean. Check throttle body bore for foreign material. Reset IAC using scan tool.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) , then go to next step.
  2. Replace VCM. Program replacement VCM using required equipment and perform Crankshaft Variation Learn Procedure. After replacing VCM, go to next step.
  3. Using scan tool, select DTC and CLEAR DTC INFO function. Warm engine to normal operating temperature. Operate engine at idle. Using scan tool, select DTC and SPECIFIC DTC function, then enter this DTC. Operate vehicle within 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).
  4. Check if any additional DTC(s) are present. If additional DTCs are present, diagnose affected DTC(s) first. If no other DTCs are present, system is okay.

Replace VCM even if this DTC exists only in history.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) , then go to next step.
  2. Turn ignition on, engine off. Using scan tool, attempt to establish communications with VTD control module. If scan tool communicates with VTD control module, go to next step. If scan tool cannot communicate with VTD control module, diagnose VTD system. See ANTI-THEFT SYSTEM article in ACCESSORIES/SAFETY EQUIPMENT section.
  3. Using scan tool, select ATC CONTROL MODULE function. Check if DTC U1192 is stored. If DTC U1192 is set, diagnose DTC. If DTC U1192 is not set, go to next step.
  4. Check Class II serial data circuit for open, short or faulty connection between VTD control module and VCM. Repair as necessary. After repairs, go to step 8). If circuit or connections are okay, go to next step.
  5. Turn ignition off. Reconnect all components that were disconnected earlier. Turn ignition on, engine off. Using scan tool, clear all DTCs. Turn ignition off for about 15 minutes. Turn ignition on, engine off. Check if DTC resets. If DTC resets, go to next step. If DTC does not reset, go to step 7).
  6. Replace VCM. Program replacement VCM using required equipment and then perform Crankshaft Variation Learn Procedure. After replacing VCM, go to step 8).
  7. DTC is intermittent. Check if additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  8. Turn ignition off. Reconnect or reinstall components that were previously disconnected/removed. Using scan tool, clear DTCs. Check if additional DTCs are present. Diagnose affected DTCs. If no additional DTCs are present, system is okay.

DO NOT clear DTCs unless directed by diagnostic procedure. Clearing DTCs will also clear valuable FREEZE FRAME and FAILURE RECORDS data. Check circuits and terminals that can cause an intermittent condition.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) , then go to next step.
  2. Unless sent here after replacing VCM, check for any BCM DTCs being set. If a BCM DTC is set, diagnose DTC. See BODY CONTROL MODULE article in ACCESSORIES/SAFETY EQUIPMENT section. If T-50/T-60 scan tool is being used, go to step 5). If T-50/T-60 scan tool is not being used, go to next step.
  3. If Tech 2 scan tool is being used, go to step 6). If Tech 2 scan tool is not being used, go to next step. NOTE: While VCM is in Auto Learn Procedure, battery voltage must be maintained at all time. This procedure must be followed exactly or procedure will have to be repeated from beginning. Performing following procedures will set DTC P1630. Turn ignition off for 30 seconds, then turn ignition on. DTC P1630 should clear. If it does not, diagnose DTC P1630.
  4. Turn ignition on, with engine off for 11 minutes. Turn ignition off for 30 seconds. Repeat turning on ignition for 11 minutes, and turning it off for 30 seconds 2 times. Turn ignition on, with engine off and wait 30 seconds. Attempt to start engine. If engine starts and operates normally, go to step 7). If engine does not start or operate normally, go to step 8). NOTE: Performing following procedures will set DTC P1630. Turn ignition off for 30 seconds, then turn ignition on. DTC P1630 should clear. If it does not, diagnose DTC P1630.
  5. Using T-50/T60 scan tool, enter SERVICE PROGRAMMING SYSTEM. Select TERMINAL-TO-VEHICLE PROGRAMMING. Select DONE and follow instructions on VEHICLE SET-UP screen. Select VEHICLE THEFT RELEARN. Follow instructions on remaining screens. PCM and BCM will be prepared for relearn. A security timer will be on for about 11 minutes or DTC P1630 sets. Keep terminal connected to vehicle during 11 minute period. When BCM and VCM are prepared to relearn, turn ignition off for 30 seconds and attempt to start engine. If engine starts and operates normally, go to step 7). If engine does not start or operate normally, go to step 8). NOTE: Performing following procedures will set DTC P1630. Turn ignition off for 30 seconds, then turn ignition on. DTC P1630 should clear. If it does not, diagnose DTC P1630.
  6. Using Tech 2 scan tool, enter SERVICE PROGRAMMING SYSTEM. After keying vehicle information, select REQUEST INFO key. Select DONE and follow instructions on VEHICLE SET-UP screen. Disconnect scan tool from vehicle and connect it to Techline terminal. At Techline terminal, select SERVICE PROGRAMMING SYSTEM. Select TERMINAL-TO-TECH 2 PROGRAMMING. Select DONE. Follow instructions on remaining screens. Select VEHICLE THEFT RELEARN. Select PROGRAM. Return scan tool to vehicle and connect to DLC. Select SERVICE PROGRAMMING SYSTEM. After keying vehicle information, select REQUEST INFO key. Select THEFT RELEARN. Follow instructions on remaining screens. PCM and BCM will be prepared for relearn. A security timer will be on for about 11 minutes or DTC P1630 sets. Keep terminal connected to vehicle during 11 minute period. When BCM and PCM are prepared to relearn, turn ignition off for 30 seconds and attempt to start engine. If engine starts and operates normally, go to next step. If engine does not start or operate normally, go to step 8). NOTE: Before clearing DTCs, monitor all DTC status parameters and note any additional DTCs.
  7. Using scan tool, clear VCM DTCs. Turn ignition off for 30 seconds. Attempt to start engine. If engine starts and operates normally, system is okay. If engine does not start and run, go to next step.
  8. Using scan tool, read DTCs. If DTC P1626 or P1630 is set, diagnose affected DTC(s). If DTC P1631 resets, return to step 2).
  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) , then go to next step.
  2. Turn ignition on, engine off. Using scan tool, attempt to establish communications with Active Transfer Case Control Module (ATCM). If scan tool communicates with ATCM, go to next step. If scan tool does not communicate with ATCM, diagnose ATCM. See the AUTO TRANS DIAGNOSIS article in the AUTO TRANS DIAGNOSIS section.
  3. Check for open, short to ground or short to voltage in Class II serial data circuit between VCM and ATCM. Check for damaged terminals at DLC, VCM to ATCM. Repair as necessary. After repairs, go to step 7). If circuit and connectors are okay, go to next step.
  4. Turn ignition off. Reconnect all components that were earlier disconnected. Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Turn ignition on, engine off. Check if this DTC resets. If DTC resets, go to next step. If DTC does not reset, go to step 6).
  5. Replace VCM. Program replacement VCM using required equipment and perform Crankshaft Variation Learn Procedure. After replacing VCM, go to step 7).
  6. This DTC is intermittent. Check if additional DTCs are set. Diagnose affected DTCs. If no additional DTCs are set, see DIAGNOSTIC AIDS.
  7. Turn ignition off. Reconnect all disconnected components. Using scan tool, clear DTCs. Check if any DTC(s) resets. If DTC(s) resets, repeat step 1). If DTC(s) does not reset, system is okay.

Do not clear DTCs unless directed by a diagnostic procedure. Clearing DTCs will also clear valuable Freeze Frame and Failure Records information.

Check 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.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) , then go to next step.
  2. Using scan tool, check if scan tool can communicate with EBCM. If scan tool can communicate with VCM, go to next step. If scan tool cannot communicate with EBCM, see ANTI-LOCK BRAKE SYSTEM article in BRAKES section.
  3. Using scan tool, select EBCM function. Check if DTC U1041 is stored in ATC memory. If DTC is stored, see ANTI-LOCK BRAKE SYSTEM article in BRAKES section. If DTC is not stored, go to next step.
  4. Check for short or open in Class II serial data circuit between VCM and ATC. Check for faulty connections at DLC, VCM or ATC. Repair as necessary. After repairs, go to step 8). If circuit or connections are okay, go to next step.
  5. Reconnect all components previously disconnected. Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Turn ignition on, engine off. Check if DTC resets. If DTC resets, go to next step. If DTC does not reset, go to step 7).
  6. Replace VCM. Program replacement VCM using required equipment and perform VTD and Crankshaft Variation Learn Procedure. After replacing VCM, go to next step.
  7. DTC is intermittent. Check for additional DTCs. If additional DTCs are set, diagnose affected DTCs. If no additional DTCs are set, system is okay. See DIAGNOSTIC AIDS.
  8. Turn ignition off. Reconnect all disconnected components. Using scan tool, clear all DTCs. Check if DTC resets. If DTC resets, repeat step 1). If DTC does not reset, system is okay.

Do not clear DTCs unless directed by a diagnostic procedure. Clearing DTCs will also clear valuable Freeze Frame and Failure Records information.

Check 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. Install additional ground wire from IPC to negative side of battery terminal if electrical interference is suspected.

  1. Perform «POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK»(ref-33422-S03507999212001122000000) , then go to next step.
  2. Using scan tool, check if scan tool can display data from PCM. If scan tool can display data from BCM, go to next step. If scan tool cannot display data from BCM, diagnose DLC circuit. See WIRING DIAGRAMS - 4.3L article.
  3. Using scan tool, check if scan tool can display BCM, TBC or VTD data. If scan tool can display data, go to next step. If scan tool cannot display data, diagnose electrical system. See WIRING DIAGRAMS - 4.3L article.
  4. Check for intermittent short or open in serial data circuit to BFC. Repair as necessary. After repairs, go to step 6). If circuit is okay, go to next step.
  5. Using scan tool, check for additional DTCs or communication with other modules. Diagnose or 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 the 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 for additional DTCs. If additional DTCs are set, diagnose affected DTCs. If no additional DTCs are set, system is okay. See DIAGNOSTIC AIDS.

Check 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. Install additional ground wire from IPC to negative side of battery terminal if electrical interference is suspected.

More articles — Engine Controls - Tests W/codes - 4.3L