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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 85 (ENGINE CONTROLS - SELF-DIAGNOSTICS - 8.1L)DIAGNOSTIC TESTSDTC P0106: MAP SYSTEM PERFORMANCEDIAGNOSTIC 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 13 other vehicles, including the 2002 GMC Yukon XL, 2002 GMC Sierra, 2002 GMC Savana Special, 2002 GMC Savana Camper Special, and 2002 GMC Savana. 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. Observe the MAP sensor pressure with a scan tool. Compare this value to value observed in a known-good vehicle. Is the difference between the vehicles less than 3 kPa? If yes, go to next step. If no, go to step  7.
  3. Observe the MAP sensor pressure on the scan tool. Start the engine. Does the MAP sensor change value? If yes, go to next step. If no, go to step  7.
  4. Turn OFF the ignition. Remove the MAP sensor from the vacuum source. Leave the electrical harness connected. Connect a hand vacuum pump to the MAP sensor port. Turn ON the ignition, with the engine OFF. Observe the MAP sensor pressure as you SLOWLY apply vacuum 1 in. Hg at a time. Each inch of vacuum should result in a 3-4 kPa drop in the MAP sensor pressure. Does the scan tool indicate that the MAP sensor is operating normally? If yes, go to next step. If no, go to step  15.
  5. Observe the MAP sensor pressure with 20 in. Hg applied to the MAP sensor. Does the scan tool indicate that the MAP sensor pressure is less than 34 kPa? If yes, go to next step. If no, go to step  7.
  6. Disconnect the MAP sensor from the hand vacuum pump. Does the MAP sensor pressure return to the original value that was observed in step  2? If yes, see DIAGNOSTIC AIDS . If no, go to step  15.
  7. 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 more than 0.1 V? If yes, go to step  14. If no, go to next step.
  8. Connect a 3-amp fused jumper wire between the 5-volt reference circuit of the MAP sensor and the signal circuit of the MAP sensor. Does the scan tool indicate that the MAP sensor voltage is near 5 V? If yes, go to next step. If no, go to step  13.
  9. Remove the jumper wire. Measure the voltage from the 5-volt reference circuit of the MAP sensor to a good ground. Does the voltage measure more than 5.2 V? If yes, go to step  11. If no, go to next step.
  10. Probe the low reference circuit with a test lamp connected to a battery positive voltage source. Does the test lamp illuminate? If yes, go to step  15. If no, go to step  12.
  11. Test the 5-volt reference circuit of the MAP sensor for a short to voltage. Did you find and correct the condition? If yes, go to step  19. If no, go to step  16.
  12. Test the low reference circuit of the MAP sensor for high resistance or an open. Did you find and correct the condition? If yes, go to step  19. If no, go to step  16.
  13. Test the 5-volt reference and the signal circuit of the MAP sensor for high resistance. Did you find and correct the condition? If yes, go to step  19. If no, go to step  16.
  14. 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  19. If no, go to step  16.
  15. Inspect the MAP sensor for poor connections. Did you find and correct the condition? If yes, go to step  19. If no, go to step  17.
  16. Inspect the PCM for poor connections. Did you find and correct the condition? If yes, go to step  19. If no, go to step  18.
  17. Replace the MAP sensor. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  19.
  18. Replace the PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  19. 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.
  20. 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.