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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 81 (Engine Controls - Self-Diagnostics - 8.1L) >> Diagnostic Tests >> DTC P1275: Accelerator Pedal Position Circuit - Sensor 1 >> Diagnostic Procedures

Diagnostic Procedures

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  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. NOTE: If DTCs P1120 or P1518 is also set, see DTC P1120: THROTTLE POSITION SENSOR 1 VOLTAGE OUT OF RANGE  or DTC P1518: TAC MODULE SERIAL DATA FAULT  for further diagnosis.
  2. Turn ON the ignition with the engine OFF, and with your foot OFF the accelerator pedal. With a scan tool, observe the APP sensor 1 voltage. Does the scan tool indicate APP sensor 1 voltage 0.25-2.24 V? If yes, go to next step. If no, go to step  6.
  3. Depress the accelerator pedal to the Wide Open Throttle (WOT) position. Does the scan tool indicate APP sensor 1 voltage 2.24-4.23 V? If yes, go to next step. If no, go to step  6.
  4. Turn OFF the ignition for 30 seconds. Turn ON the ignition, with the engine OFF. Select the Diagnostic Trouble Code (DTC) option using the scan tool. Lightly touch and move the related engine wiring harnesses and connectors while monitoring the DTC Information. Did this DTC fail this ignition cycle, during the above test? If yes, go to step  24. If no, go to next step.
  5. Continue to observe the DTC Information. Depress the accelerator pedal to WOT and then return the pedal to the released position. Did this DTC fail this ignition cycle, during the above test? If yes, go to step  19. If no, see DIAGNOSTIC AIDS .
  6. Disconnect the APP sensor harness connector. Does the scan tool indicate APP sensor 1 voltage at 0 V? If yes, go to next step. If no, go to step  11.
  7. Connect a test lamp between the APP sensor 1 signal circuit and battery voltage. Does the scan tool indicate APP sensor 1 voltage at 5 V? If yes, go to next step. If no, go to step  13.
  8. With a Digital Multimeter (DMM), test the APP sensor 1, 5-volt reference circuit for voltage. Does the DMM indicate voltage is 4.6-5.4 V? If yes, go to step  10. If no, go to next step.
  9. Turn OFF the ignition. Disconnect the throttle actuator motor harness connector. Remove the air inlet duct from the throttle body assembly. Turn ON the ignition, with the engine OFF. Rotate the throttle blade by hand to WOT and hold. With a DMM, test the APP sensor 1, 5-volt reference circuit for voltage. Does the DMM indicate voltage is 4.6-5.4 V? If yes, go to step  21. If no, go to step  16.
  10. Connect a fused jumper between the APP sensor 1 low reference circuit and the APP sensor 1, 5-volt reference circuit. With a scan tool, observe the TP sensor 1 voltage parameter. Does the scan tool indicate TP sensor 1 voltage at 0 V? If yes, go to step  19. If no, go to step  17.
  11. Turn OFF the ignition. Disconnect the TAC module harness connector containing the APP sensor circuits. Turn ON the ignition, with the engine OFF. With a DMM, test the APP sensor 1 signal circuit for a short to voltage. Did you find and correct the condition? If yes, go to step  25. If no, go to next step.
  12. Turn OFF the ignition. Disconnect the other TAC module harness connector. With a DMM, test for a short between the APP sensor 1 signal circuit and all other TAC module circuits. Did you find and correct the condition? If yes, go to step  25. If no, go to step  22.
  13. Turn OFF the ignition. Disconnect the TAC module harness connector containing the APP sensor circuits. With a DMM, test the APP sensor 1 signal circuit for an open or high resistance. Did you find and correct the condition? If yes, go to step  25. If no, go to next step.
  14. With a DMM, test the APP sensor 1 signal circuit for a short to ground. Did you find and correct the condition? If yes, go to step  25. If no, go to next step.
  15. Turn OFF the ignition. Disconnect the other TAC module harness connector. With a DMM, test for a short between the APP sensor 1 signal circuit and all other TAC module circuits. Did you find and correct the condition? If yes, go to step  25. If no, go to step  22.
  16. Turn OFF the ignition. Disconnect the TAC module connector containing the APP sensor circuits. With a DMM, test the APP sensor 1, 5-volt reference circuit for an open or high resistance. Did you find and correct the condition? If yes, go to step  25. If no, go to step  22.
  17. Disconnect the TAC module connector containing the APP sensor circuits. With a DMM, test the APP sensor 1 low reference circuit for an open or high resistance. Did you find and correct the condition? If yes, go to step  25. If no, go to next step.
  18. With a DMM, test the TAC module ground circuit for an open or high resistance. Did you find and correct the condition? If yes, go to step  25. If no, go to step  22.
  19. Inspect for poor connections at the harness connector of the APP sensor. Did you find and correct the condition? If yes, go to step  25. If no, go to next step.
  20. Replace the APP sensor assembly. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  25.
  21. Did DTC P1120 set while performing step  9? If yes, see DTC P1120: THROTTLE POSITION SENSOR 1 VOLTAGE OUT OF RANGE . If no, go to next step.
  22. Inspect for poor connections at the harness connector of the TAC module. Did you find and correct the condition? If yes, go to step  25. If no, go to next step.
  23. Replace the TAC module. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  25.
  24. Repair the intermittent condition as necessary. After repairs, go to next step.
  25. 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.
  26. 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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