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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 108 (ENGINE CONTROL SYSTEM SELF-DIAGNOSTICS - 3.8L)DIAGNOSTIC TESTSDTC P0102: MAF SENSOR CIRCUIT - LOW FREQUENCYDIAGNOSTIC PROCEDURES
2003 Chevrolet TrailBlazer 4.2 S, 4WD

Diagnostic Procedures

2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Diagnostic Procedures
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2002 Pontiac Grand Prix, 2002 Pontiac Bonneville, 2002 Chevrolet Monte Carlo, 2002 Chevrolet Impala, and 2002 Buick Regal. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform Diagnostic System Check - Engine Controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM. After performing Diagnostic System Check - Engine Controls, go to next step.
  2. Start the engine. Observe the MAF sensor frequency with a scan tool. Is the MAF sensor frequency less than 1200 Hz? If yes, go to step  4. 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 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. Observe the MAF sensor frequency 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 frequency? If yes, go to step  25. If no, go to next step.
  5. Turn OFF the ignition. Inspect for the following conditions:
    • A restricted air intake duct.
    • A collapsed air intake duct.
    • A dirty air filter element.
    • A deteriorating air filter element.
    • Any objects blocking the air inlet screen of the MAF sensor.
    • Any debris on the sensing elements of the MAF sensor.
    • Any vacuum leak downstream 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  30. If no, go to next step.

  6. Inspect the fuse in the ignition 1 voltage circuit of the MAF sensor. Is the fuse open? If yes, go to step  12. If no, go to next step.
  7. Turn on the ignition, with the engine off. Disconnect the MAF sensor. Connect a test lamp between the ignition 1 voltage circuit of the MAF sensor and a good ground. Connect the DMM to the probe of the test lamp and a good ground. Is the voltage less than battery voltage? If yes, go to step  19. If no, go to next step.
    8. NOTE: All electrical components and accessories must be turned off.
  8. Turn off the ignition for 60 seconds to allow the control modules to power down. Measure the resistance from the ground circuit of the MAF sensor to a good ground with a DMM. Is the resistance less than 5 ohms? If yes, go to next step. If no, go to step  19.
  9. Turn on the ignition, with the engine off. Measure the voltage from the signal circuit of the MAF sensor to a good ground with a DMM. Is the voltage near 5 volts? If yes, go to next step. If no, go to step  11.
  10. Connect a 3-amp fused jumper wire between the signal circuit of the MAF sensor and a good ground. Start the engine. Do any additional DTCs set? If yes, go to step  23. If no, go to step  26.
  11. Is the voltage less than 4.5 volts? If yes, go to step  13. If no, go to step  15.
    12. NOTE: The ignition 1 voltage circuit of the MAF sensor is spliced to other components of the vehicle.
  12. Test for continuity between the ignition 1 voltage circuit of the MAF sensor and ground. Does the DMM indicate continuity? If yes, go to step  17. If no, go to step  26.
  13. Turn off the ignition. Disconnect the PCM. Test the signal circuit between the PCM and the MAF sensor for the following conditions:
    • A high resistance.
    • An open circuit.

    Does the DMM indicate continuity? If yes, go to next step. If no, go to step  20.

  14. Test for continuity from the signal circuit of the MAF sensor to ground. Does the DMM indicate continuity? If yes, go to step  21. If no, go to step  16.
    15. NOTE: Disconnecting the PCM connectors may eliminate the short to voltage if the signal circuit is shorted to another PCM circuit.
  15. Turn OFF the ignition. Disconnect the PCM. Turn on the ignition, with the engine off. Measure the voltage from the signal circuit of the MAF sensor to a good ground. Is the voltage near 0 volts? If yes, go to next step. If no, go to step  22.
  16. Test for continuity at the harness connector of the PCM from the signal circuit of the MAF sensor to all other circuits at both PCM connectors. Does the DMM indicate continuity between any other circuit? If yes, go to step  24. If no, go to step  27.
  17. Repair the short to ground in the ignition 1 voltage circuit of the MAF sensor. Replace the fuse if necessary. After repairs, go to step  30.
  18. Repair the open in the ignition 1 voltage circuit of the MAF sensor. After repairs, go to step  30.
  19. Repair the high resistance or an open in the MAF sensor ignition 1 voltage circuit. After repairs, go to step  30.
  20. Repair the high resistance or an open in the signal circuit of the MAF sensor. After repairs, go to step  30.
  21. Repair the short to ground in the signal circuit of the MAF sensor. After repairs, go to step  30.
  22. Repair the short to voltage in the signal circuit of the MAF sensor. After repairs, go to step  30.
  23. Repair the short between the signal circuit of the MAF sensor and the circuit for which the DTC set. After repairs, go to step  30.
  24. Repair the circuits that are shorted together. After repairs, go to step  30.
  25. Repair the harness or the connections as needed. After repairs, go to step  30.
  26. Test for an intermittent and for a poor connection at the MAF sensor. Did you find and correct the condition? If yes, go to step  30. If no, go to step  28.
  27. Test for an intermittent and for a poor connection at the PCM. Did you find and correct the condition? If yes, go to step  30. If no, go to step  29.
  28. Replace the MAF sensor. After repairs, go to step  30.
  29. Replace PCM. Program replacement PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  30. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within Conditions for Running DTC. Does DTC run and pass? If yes, go to next step. If no, go to step  2.
  31. Using scan tool, observe stored information. Does scan tool displays any DTCs that have not been diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.