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Home >> GMC >> 2003 >> Jimmy 2D Utility, Part Time, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics - 4.3L >> Diagnostic Tests >> DTC P0121: TP Sensor Performance >> Diagnostic Procedures

Diagnostic Procedures

  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. Inspect for disconnected, damaged or misrouted vacuum hoses. Inspect MAP sensor for missing or damaged seal, restrictions in MAP sensor vacuum source, or intake manifold vacuum leaks. Did you find and correct the condition? If yes, go to step  24. If no, go to next step.
    3. NOTE: The vehicle used for the comparison is not limited to the same type of vehicle as is being serviced. A vehicle known to provide an accurate reading is acceptable.
  3. Do you have access to another vehicle in which the MAP sensor pressure can be observed with a scan tool? If yes, go to next step. If no, go to step  5.
  4. Turn ignition on, with engine off. Observe the MAP sensor pressure with a scan tool. Observe the MAP sensor pressure in the known-good vehicle with a scan tool. Compare the values. Is the difference between the values less than 3 kPa? If yes, go to step  6. If no, go to DTC P0106: MAP SYSTEM PERFORMANCE .
    5. NOTE: The Altitude vs. Barometric Pressure table indicates a pressure range for a given altitude under normal weather conditions. Weather conditions consisting of very low or very high pressure and/or very low or very high temperature may cause a reading to be slightly out of range.
  5. Turn ignition on, with engine off. Observe the MAP sensor pressure with a scan tool. Refer to Altitude vs Barometric Pressure table in SENSOR OPERATING RANGE CHARTS - TRUCKS article. The MAP sensor pressure should be within the range specified for your altitude. Does the MAP sensor indicate the correct barometric pressure? If yes, go to next step. If no, go to DTC P0106: MAP SYSTEM PERFORMANCE .
  6. Observe the MAP sensor pressure with a scan tool. Start engine. Does the MAP sensor pressure change? If yes, go to next step. If no, go to DTC P0106: MAP SYSTEM PERFORMANCE .
  7. Turn ignition off. Turn ignition on, with engine off. Observe the TP sensor parameter with a scan tool. Is the voltage less than the 0.90 volt with the throttle in the closed position? If yes, go to next step. If no, go to step  9.
  8. Observe the TP sensor parameter with scan tool. Depress the accelerator pedal slowly until the throttle is in the wide open position. Release the accelerator pedal slowly until the throttle is returned to the closed position. Repeat this procedure several times. Does the TP sensor parameter increase steadily, when the pedal is depressed, to more than 98 percent and then decrease steadily when pedal is released, returning to less than 1 percent? If yes, problem is intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 4.3L ASTRO, BLAZER, JIMMY CANADIAN, SAFARI, SONOMA & S10 PICKUP article. If no, go to step  10.
  9. Inspect throttle body for throttle blade binding or damaged, cruise control cable binding or damaged, or throttle cable binding or damaged. Did you find and correct the condition? If yes, go to step  24. If no, go to next step.
  10. Disconnect the TP sensor electrical connector. Observe the TP sensor parameter with the scan tool. Is the voltage less than 0.1 volt? If yes, go to next step. If no, go to step  15.
  11. Measure the voltage from the 5-volt reference circuit of the TP sensor to a good ground with a DVOM. Is the voltage more than 5.2 volts? If yes, go to step  16. If no, go to next step.
  12. Probe the 5-volt reference circuit of the TP sensor with a test light that is connected to a good ground. Is the test light OFF? If yes, go to step  17. If no, go to next step.
  13. Connect a 3-amp fused jumper wire between the 5-volt reference circuit of the TP sensor and the signal circuit of the TP sensor. Observe the TP sensor parameter with the scan tool. Is the voltage more than 4.9 volts? If yes, go to next step. If no, go to step  18.
  14. Turn ignition off. Remove the jumper wire. Connect a jumper wire between each of the terminals in the TP sensor harness connector and the corresponding terminal at the TP sensor. Turn ignition on, with engine off. Measure the voltage from the low reference circuit of the TP sensor at the jumper wire terminal to a good ground with a DVOM. Is voltage more than 0.2 volt? If yes, go to step  19. If no, go to step  20.
    15. NOTE: Disconnecting the PCM may eliminate the short during testing.
  15. Test the TP sensor signal circuit between the PCM and TP sensor for a short to voltage. Did you find and correct the condition? If yes, go to step  24. If no, go to step  23.
    16. NOTE: Disconnecting the PCM may eliminate the short during testing.
  16. Test all of the branches of the 5-volt reference circuit that are shared with the TP sensor for a short to voltage. Did you find and correct the condition? If yes, go to step  24. If no, go to step  23.
  17. Test the 5-volt reference circuit between the PCM and TP sensor for an open or for high resistance. Did you find and correct the condition? If yes, go to step  24. If no, go to step  21.
  18. Test the TP sensor signal circuit between the PCM and TP sensor for a short to ground, open or high resistance. Did you find and correct the condition? If yes, go to step  24. If no, go to step  21.
  19. Test the low reference circuit between the PCM and TP sensor for an open or for high resistance. Did you find and correct the condition? If yes, go to step  24. If no, go to step  21.
  20. Test for an intermittent and for a poor connection at the TP sensor. Did you find and correct the condition? If yes, go to step  24. If no, go to step  22.
  21. Test for an intermittent and for a poor connection at the PCM. Did you find and correct the condition? If yes, go to step  24. If no, go to step  23.
  22. Replace TP sensor. See appropriate REMOVAL & INSTALLATION article. After repairs, go to step  24.
  23. Replace PCM. See appropriate REMOVAL & INSTALLATION article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  24. Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start engine. Operate the vehicle within the Conditions for Running DTC. See CONDITIONS FOR RUNNING DTC . Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  25. 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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