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Diagnostic Procedures

WARNING: This page is about a different car, the 2002 GMC Sierra, 2002 GMC Cab & Chassis Sierra, 2002 Chevrolet Silverado, and 2002 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you perform the Diagnostic System Check-Engine Controls? If yes, go to next step. If no, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. Start the engine Monitor the Diagnostic Trouble Code (DTC) Information using the scan tool. Does the scan tool display any other DTCs set? If yes, diagnose those DTCs first. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, go to next step.
  3. Observe the Freeze Frame/Failure Records data for this DTC. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC as specified in the supporting text or as close to the Freeze Frame/Failure Records data that you observed. Does the DTC fail this ignition cycle? If yes, go to next step. If no, see DIAGNOSTIC AIDS .
  4. Inspect the fuse in the ignition 1 voltage circuit of the MAF sensor. Is the fuse open? If yes, go to step  17. If no, go to next step.
  5. Turn OFF the ignition. Inspect for air leaks in the following components:
    • The air induction system and the turbocharger system.
    • The MAF sensor O-ring seal.
    • The boost pressure sensor seal.
    • The EGR throttle valve solenoid, diaphragm, or vacuum hose.
    • The EGR valve solenoid valve diaphragm, or vacuum hose.
    • The EGR vent solenoid or vacuum hose.

    Inspect for the following conditions:

    • Any kinks or restrictions in any of the EGR solenoid vacuum hoses.
    • An obstructed intake air duct or a dirty air filter element.
    • Any debris that is blocking the air sensing filaments of the MAF sensor.
    • A MAF sensor that is installed backwards.
    • A restricted exhaust system.

    Did you find and correct the condition? If yes, go to step  26. If no, go to next step.

  6. Turn ON the ignition, with the engine OFF. Observe both the BARO kPa and the boost pressure sensor kPa with a scan tool. Does the scan tool indicate that the difference between the sensors is equal to or less than 8 kPa? If yes, go to next step. If no, see DTC P0107: MAP SENSOR CIRCUIT - LOW VOLTAGE (CA) , DTC P0107: BARO SENSOR CIRCUIT - LOW PRESSURE (FED) , DTC P0108: BARO SENSOR CIRCUIT - HIGH PRESSURE (FED)  or DTC P0108: MAP SENSOR CIRCUIT - HIGH VOLTAGE (CA)  .
  7. Start the engine and allow the engine to idle. Observe the MAF sensor g/s with a scan tool. Move the harness and the connector of the MAF sensor. Does the movement of the harness or the connector affect the MAF sensor g/s? If yes, go to step  21. If no, go to next step.
  8. Observe the MAF sensor g/s with a scan tool. Is the MAF sensor g/s less than 16 g/s? If yes, go to step  11. If no, go to next step.
  9. Observe the MAF sensor g/s with a scan tool. Is the MAF sensor g/s more than 445 g/s? If yes, go to next step. If no, go to step  11.
  10. Disconnect the harness connector of the MAF sensor. Is the MAF sensor g/s more than 445 g/s? If yes, go to step  15. If no, go to next step.
  11. Turn OFF the engine. Turn ON the ignition, with the engine OFF. Disconnect the harness connector of the MAF sensor. Connect a test lamp between the ignition 1 voltage circuit of the MAF sensor and a good ground. Does the test lamp illuminate? If yes, go to next step. If no, go to step  17.
  12. Connect a test lamp between the ignition 1 voltage circuit of the MAF sensor and the low reference circuit of the MAF sensor. Does the test lamp illuminate? If yes, go to next step. If no, go to step  18.
  13. Connect a 3-amp fused jumper wire between the signal circuit of the IAT sensor and the signal circuit of the MAF sensor. Observe the MAF sensor value with a scan tool. Did the MAF sensor value change to 499 g/s? If yes, go to step  22. If no, go to next step.
  14. Turn OFF the ignition. Disconnect the fused jumper wire. Disconnect the ECM. Test the signal circuit between the ECM and the MAF sensor for the following conditions:
    • A high resistance or an open.
    • A short to ground.
    • A short to the low reference circuit of the MAF sensor or IAT sensor.
    Did you find and correct the condition? If yes, go to step  26. If no, go to step  16.
    15. NOTE: Disconnecting the ECM connectors may eliminate the short to voltage if the signal circuit is shorted to another ECM circuit.
  15. Turn OFF the ignition. Disconnect the ECM. Turn ON the ignition, with the engine OFF. Measure the voltage from the signal circuit of the MAF sensor to a good ground. Does the voltage measure near 0 V? If yes, go to next step. If no, go to step  19.
  16. Use a Digital Multimeter (DMM) in order to test for continuity at the harness connector of the ECM from the signal circuit of the MAF sensor to all other circuits at both ECM connectors. Does the DMM indicate continuity between any other circuit? If yes, go to step  20. If no, go to step  23.
  17. Repair the short to ground or an open in the ignition 1 voltage circuit of the MAF sensor. Replace the fuse if necessary. Did you complete the repair? If yes, go to step  26. If no, go to step  24.
  18. Repair the high resistance or an open in the low reference circuit of the MAF sensor. Did you complete the repair? If yes, go to step  26. If no, go to step  23.
  19. Repair the short to voltage in the signal circuit of the MAF sensor. After repairs, go to step  26.
  20. Repair the circuits that are shorted together. After repairs, go to step  26.
  21. Repair the harness or the connections as necessary. After repairs, go to step  26.
  22. Inspect for poor connections at the harness connector of the MAF sensor. Did you find and correct the condition? If yes, go to step  26. If no, go to step  24.
  23. Inspect for poor connections at the harness connector of the ECM. Did you find and correct the condition? If yes, go to step  26. If no, go to step  25.
  24. Replace the MAF/IAT sensor. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  26.
  25. Replace the ECM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Reprogram ECM. See ENGINE CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  26. Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC. Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  27. Observe the stored information, Capture Info with a scan tool. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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