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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 218 (ENGINE CONTROL SYSTEM - SELF-DIAGNOSTICS)DIAGNOSTIC TESTSDTC P0120: TP SENSOR CIRCUITDIAGNOSTIC PROCEDURES
2003 Chevrolet TrailBlazer 4.2 S, 4WD

Diagnostic Procedures

2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Diagnostic Procedures
WARNING: This page is about a different car, the 2003 Pontiac Vibe. 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, perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. Install scan tool. With throttle closed, select TP sensor parameter on scan tool. Is TP sensor percentage 7-11 percent? If yes, go to next step. If no, go to step  4.
  3. Use scan tool to clear DTCs. Turn ignition switch to OFF position for 30 seconds. Start engine. Operate vehicle within freeze frame conditions as specified. Does DTC P0120 set? If yes, go to next step. If no, see DIAGNOSTIC AIDS .
  4. Is a DTC P0110 or DTC P0115 also set? If yes, go to step  13. If no, go to next step.
  5. Observe TP sensor parameter with throttle closed. Is TP sensor percentage near 99 percent? If yes, go to step  10. If no, go to next step.
  6. Observe TP sensor parameter with throttle closed. Is TP sensor percentage less than 2 percent? If yes, go to next step. If no, go to DIAGNOSTIC AIDS .
  7. Disconnect TP sensor harness connector. Jump 5-volt reference circuit and TP sensor input circuit together at TP sensor harness connector. Select TP sensor on scan tool. Is TP sensor percentage more than 90 percent? If yes, go to step  16. If no, go to next step.
  8. Connect a test light between battery voltage and TP sensor input circuit at TP sensor harness connector. Observe TP sensor on scan tool. Is TP sensor percentage more than 90 percent? If yes, go to next step. If no, go to step  14.
  9. Check TP sensor 5-volt reference circuit for an open. Repair as necessary. Did you find and repair a condition? If yes, go to step  20. If no, go to step  18.
  10. Disconnect TP sensor harness connector. Observe TP sensor parameter on scan tool. Is TP sensor percentage at zero percent? If yes, go to next step. If no, go to step  12.
  11. Connect a test light between battery voltage and TP sensor ground circuit. Did test light illuminate? If yes, go to step  17. If no, go to step  15.
  12. Check for a short to voltage in TP sensor input circuit. Repair as necessary. Did you find and repair a condition? If yes, go to step  20. If no, go to step  19.
  13. Check for an open in TP sensor ground circuit between splice S108 and PCM. Repair as necessary. Did you find and repair a condition? If yes, go to step  20. If no, go to step  18.
  14. Check TP sensor input circuit for an open or a short to ground. Repair circuit as necessary. Did you find and repair a condition? If yes, go to step  20. If no, go to step  18.
  15. Repair open in TP sensor ground circuit between sensor and splice S108. After repair, go to step  20.
  16. Check for an intermittent or a poor electrical connection at TP sensor. Repair as necessary. Did you find and repair a condition? If yes, go to step  20. If no, go to next step.
  17. Replace TP sensor. After repair, go to step  20.
  18. Check for an intermittent or a poor electrical connection at PCM. Repair as necessary. Did you find and repair a condition? If yes, go to step  20. If no, go to next step.
  19. Replace PCM. After repair, go to step  20.
  20. With a scan tool, observe stored information, CAPTURE INFO. Does scan tool display any DTCs that you have not diagnosed? If yes, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are present, system is okay at this time.
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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.