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Home >> Pontiac >> 2003 >> Vibe Base, AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - System & Component Testing >> Idle Control Systems >> Electrical/Accessory Load Idle-Up Signal Diagnosis >> Diagnostic Testing
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Diagnostic Testing

  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 in SELF-DIAGNOSTICS - 1.8L VIBE article.
    2. NOTE: Ensure the rear defogger and the parking lights operate correctly before proceeding.
  2. Connect scan tool. Start the engine. Run vehicle at idle with the accessories OFF, until normal operating temperature is reached. Monitor the IAC MOTOR COMMAND parameter on the scan tool while turning the rear defogger switch ON and OFF. Does the scan tool indicate IAC motor command increased 1-3 percent when the rear defogger switch was turned ON? If yes, go to next step. If no, go to step  18 .
  3. Monitor the IAC MOTOR COMMAND parameter on the scan tool while turning the parking light switch ON and OFF. Does the scan tool indicate IAC motor command increased 1-3 percent when the parking light switch was turned ON? If yes, go to next step. If no, go to step  20 .
  4. Monitor the IAC MOTOR COMMAND parameter on the scan tool. Turn the A/C switch ON and blower speed selector switch to any position except OFF. Does IAC motor command increase 4-14 percent when the A/C is turned ON? If yes, go to next step. If no, go to step  10 .
  5. Monitor the IAC MOTOR COMMAND parameter on the scan tool. Turn the steering wheel to the right and to the left. Return steering wheel to the center, straight ahead position. Did the scan tool indicate IAC Motor Command increased 2-10 percent when the steering wheel was turned all the way in either direction? If yes, system is okay at this time. If no, go to next step.
  6. Turn ignition switch to RUN position, engine OFF. Disconnect PSP switch harness connector. Measure voltage from PSP switch harness connector to ground using a DMM. Is voltage near battery voltage? If yes, go to next step. If no, go to step  8 .
  7. Connect a test light to battery voltage. Probe PSP switch connector (component side) with the test light. Start the engine. Observe the test light while turning the steering wheel to the right and to the left. Does the test light illuminate when the steering wheel is turned to the right and to the left? If yes, go to step  22 . If no, go to step  9 .
  8. Check for an open or a short to ground in the PSP switch signal circuit between PCM and PSP switch. Repair as necessary. Did you find and correct a condition? If yes, go to step  25 . If no, go to step  24 .
  9. Check for a faulty ground connection at the power steering pump. Repair as necessary. Did you find and correct a condition? If yes, go to step  25 . If no, go to step  23 .
  10. Start the engine. Turn ON the HVAC blower switch to any speed. Turn the A/C switch OFF. Is the A/C compressor clutch engaged? If yes, go to step  14 . If no, go to next step.
  11. Continue to run the engine with HVAC blower ON and the A/C OFF. Backprobe the A/C clutch relay control circuit at the PCM connector using a DMM connected to ground. Measure the voltage. Does the voltage equal battery voltage? If yes, go to next step. If no, go to step  17 .
  12. Turn A/C ON. Backprobe the A/C clutch relay control circuit at the PCM connector using a DMM connected to ground. Measure the voltage. Did the voltage drop to 0.0-1.0 volt when the A/C was turned ON? If yes, go to next step. If no, go to step  24
  13. Did the A/C compressor engage when the A/C was turned ON? If yes, go to step  24 . If no, go to step  16 .
  14. Check for a short to ground in the A/C clutch relay control circuit between PCM and A/C compressor clutch relay. Repair as necessary. Did you find and correct a condition? If yes, go to step  25 . If no, go to next step.
  15. Turn ignition switch to OFF position. Disconnect PCM 35-pin harness connector C3. Start the engine. Turn ON the HVAC blower switch to any speed. Is the A/C compressor engaged? If yes, see appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING.
  16. There is a fault in an HVAC electrical circuit or component. Inspect and repair as necessary. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING. After repair, go to step  25 .
  17. There is no ignition positive voltage at the A/C clutch relay control circuit. Check for an open in the A/C clutch relay control circuit between the PCM and the A/C compressor clutch relay or for a faulty A/C compressor clutch relay or repair the cause of no ignition positive voltage to the relay. See appropriate MANUAL or AUTOMATIC A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING. After repair, go to step  25 .
  18. Turn ignition switch to RUN position, engine OFF. Backprobe the electrical load idle-up signal defogger circuit at the PCM connector using a test light connected to ground. Turn rear defogger switch ON. Does the test light illuminate? If yes, go to step  22 . If no, go to appropriate REAR WINDOW DEFOGGERS article in ACCESSORIES & EQUIPMENT.
  19. Turn ignition switch to OFF position. Check the electrical load idle-up signal defogger circuit for an open or a short. Repair as necessary. Did you find and correct a condition? If yes, go to step  25 . If no, go to step  21 .
  20. Turn ignition switch to RUN position, engine OFF. Backprobe the electrical load idle-up signal taillights circuit at the PCM connector using a test light connected to ground. Turn parking lights ON. Does the test light illuminate? If yes, go to step  22 . If no, go to next step.
  21. Turn ignition switch to OFF position. Test the electrical load idle-up signal taillights circuit for an open or a short. Repair as necessary. See EXTERIOR LIGHTS in SYSTEM WIRING DIAGRAMS article in ELECTRICAL. If you found and corrected the condition, go to step  25 .
  22. Test for a short to ground in the diagnostic request circuit from the PCM and the Data Link Connector (DLC). Repair as necessary. Did you find and correct a condition? If yes, go to step  25 . If no, go to step  24 .
  23. Replace the PSP switch. After repair, go to  25 .
  24. Replace the PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL & INSTALLATION - VIBE article. After repair, go to next step  25 .
  25. Operate the vehicle within the conditions that the concern was first noticed. Does the system now operate properly? If yes, system is okay at this time. If no, go to DIAGNOSTIC AIDS  .
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