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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 115 (ENGINE CONTROLS SELF-DIAGNOSTICS)DIAGNOSTIC TESTSDTC P1106: MAP SYSTEM PERFORMANCEDIAGNOSTIC PROCEDURE
2003 Chevrolet TrailBlazer 4.2 S, 4WD

Diagnostic Procedure

2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Diagnostic Procedure
WARNING: This page is about a different car, the 2002 Pontiac Montana, 2002 Oldsmobile Silhouette, and 2002 Chevrolet Venture. 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. Install a scan tool. Start the engine. Monitor the Diagnostic Trouble Code (DTC) information using the scan tool. Does the scan tool display DTC P0108 or P1635 set? If yes, see DTC P0108: MAP SENSOR CIRCUIT - HIGH VOLTAGE  or DTC P1635: 5-VOLT REFERENCE A CIRCUIT  . If no, go to next step.
  3. Does the scan tool indicate that the MAP sensor voltage is more than 4.2 V? If yes, go to step  5. If no, go to next step.
  4. With a scan tool, observe the MAP sensor voltage, while moving the following components:
    • The MAP sensor connector.
    • The wiring harness related to the MAP sensor.
    • The PCM connector.

    Does the scan tool indicate that the MAP sensor voltage is more than 4.2 V and holding? If yes, go to next step. If no, go to step  11.

  5. Turn OFF the ignition. Disconnect the MAP sensor electrical connector. Turn ON the ignition, with the engine OFF. Does the scan tool indicate that the MAP sensor voltage is less than 0.1 V? If yes, go to next step. If no, go to step  7.
  6. Disconnect the electrical connector of the Engine Coolant Temperature (ECT) sensor. Connect a test lamp to battery voltage. Probe the low reference circuit of the MAP sensor with the test lamp. Does the test lamp illuminate? If yes, go to step  9. If no, go to step  8.
  7. Test the signal circuit of the MAP sensor for a short to voltage. Did you find and correct the condition? If yes, go to step  11. If no, go to step  10.
  8. Test the low reference circuit of the MAP sensor for an open. Did you find and correct the condition? If yes, go to step  11. If no, go to step  10.
  9. Inspect for poor connections at the MAP sensor. Did you find and correct the condition? If yes, go to step  11. If no, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.
  10. Inspect for poor connections at the PCM. Did you find and correct the condition? If yes, go to next step. If no, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.
  11. 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.
  12. 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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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.