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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 274 (Engine Controls - Self-Diagnostics - 2.2L) >> Diagnostic Tests >> DTC P1271: Accelerator Pedal Position Sensor No. 1 & 2 Performance >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2003 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
  2. Observe the DTC information with a scan tool. Is DTC P1635 or P1639 also set? If yes, go to DTC P1635: 5-VOLT REFERENCE 1 CIRCUIT  or DTC P1639: 5-VOLT REFERENCE 2 CIRCUIT  . If no, go to next step.
  3. Turn ignition off. Disconnect the APP sensor electrical connector. Disconnect the ECM harness connector. Using a DVOM, measure resistance of the APP sensor low reference circuit, signal circuit and 5-volt reference circuit. Did any of the circuits measure greater than 5 ohms? If yes, go to step  7. If no, go to next step.
  4. Test signal circuit of the APP sensor No. 1 for a short to the signal circuit of the APP sensor No. 2. Did you find and correct the condition? If yes, go to step  9. If no, go to next step.
  5. Test for an intermittent and for a poor connection at the accelerator pedal harness connector. Did you find and correct the condition? If yes, go to step  9. If no, go to next step.
  6. Test for an intermittent and for a poor connection at the ECM harness connector. Did you find and correct the condition? If yes, go to step  8. If no, go to next step.
  7. Repair the high resistance in the circuit. After repairs, go to step  9.
  8. Replace APP sensor. After replacing sensor, go to next step.
  9. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Operate vehicle within the conditions for running the DTC. See CONDITIONS FOR RUNNING DTC . You may also operate vehicle within the conditions observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition? If yes, go to step  2. If no, go to next step.
  10. With a scan tool, observe the stored information, Capture Info. 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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