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Home >> Chevrolet >> 2002 >> Prizm Base, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System & Component Testing >> Idle Control System >> Electrical/Accessory Load Idle-Up Signal Diagnosis >> Diagnostic Procedures
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Diagnostic Procedures

  1. Perform Diagnostic System Check - Engine Controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article. After performing diagnostic system check, go to next step.
    2. NOTE: Check that the rear defogger and the parking lamps operate correctly before using this procedure.
  2. Install a 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 that the 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  19 .
  3. Monitor the IAC Motor Command parameter on the scan tool while turning the parking lamp switch ON and OFF. Does the scan tool indicate that the IAC Motor Command increased 1-3 percent when the parking lamp switch was turned ON? If yes, go to next step. If no, go to step  21 .
  4. Install a scan tool. Start the engine. Run the engine until a normal operating temperature is reached. Turn OFF all accessories. Monitor the IAC Motor Command parameter on the scan tool. Turn the A/C switch ON and the blower speed selector switch to any position except OFF. Does the IAC Motor Command increase within 4-14 percent when the A/C is turned ON? If yes, go to next step. If no, go to step  10 .
  5. Install a scan tool. Start the engine. Run the engine until a normal operating temperature is reached. Turn OFF all accessories. Monitor the IAC Motor Command parameter on the scan tool. Turn the steering wheel to the right and to the left. Return the steering wheel to the center, straight ahead position. Did the scan tool indicate that the IAC Motor Command increased 2-10 percent when the steering wheel was turned all the way in either direction? If yes, system is okay. If no, go to next step.
  6. Turn ON the ignition, with the engine OFF. Disconnect the PSP switch electrical connector. Measure the voltage from the PSP switch connector to ground on the harness side with a DMM. Is the voltage near battery voltage? If yes, go to next step. If no, go to step  8 .
  7. Connect a test lamp to battery voltage. Probe the PSP switch connector on the switch side with the test lamp. Start the engine. Observe the test lamp while turning the steering wheel to the right and to the left. Does the test lamp illuminate when the steering wheel is turned to the right and to the left? If yes, go to step  23 . If no, go to step  9 .
  8. Check for an open or a short to ground in the PSP switch signal circuit between the PCM and the PSP switch. Repair as necessary. Was a repair necessary? If yes, go to step  26 . If no, go to step  25 .
  9. Check for a faulty ground connection at the power steering pump. Repair as necessary. Was a repair necessary? If yes, go to step  26 . If no, go to step  24 .
  10. Start the engine. Turn ON the A/C. Backprobe the A/C On Signal circuit at the PCM connector with a DMM connected to ground. Measure the voltage. Is the voltage 0-1 V? If yes, go to next step. If no, go to step  13 .
  11. Start the engine. Turn OFF the A/C. Backprobe the A/C On Signal circuit at the PCM connector with a DMM connected to ground. Measure the voltage. Does the voltage equal battery voltage? If yes, go to step  14 . If no, go to next step.
  12. Turn OFF the ignition. Disconnect the PCM electrical connector. Back-out the A/C On Signal wire from the PCM electrical connector. Connect the PCM electrical connector. Turn ON the ignition, with the engine OFF. Backprobe the A/C On Signal circuit through the empty slot in the PCM electrical connector with a DMM connected to ground. Does the voltage equal battery voltage? If yes, go to next step. If no, go to step  25 .
  13. Check for an open or a short in the A/C On Signal circuit between the PCM and the A/C compressor control module. Repair as necessary. Was a repair necessary? If yes, go to step  26 . If no, go to step  18 .
  14. Start the engine. Turn OFF the A/C. Backprobe the A/C Cut-out Control circuit at the PCM connector with the DMM connected to ground. Measure the voltage. Does the voltage equal 0 V? If yes, go to next step. If no, go to step  25 .
  15. Start the engine. Turn ON the A/C. Backprobe the A/C Cut-out Control circuit at the PCM connector with the DMM connected to ground. Measure the voltage. Does the voltage equal batter voltage? If yes, see DIAGNOSTIC AIDS  . If no, go to next step.
  16. Check for an open or a short to ground in the A/C Cutout Control circuit between the PCM and the A/C compressor control module. Repair as necessary. Was a repair necessary? If yes, go to step  26 . If no, go to next step.
  17. Disconnect the electrical connector for the A/C compressor control module. Turn ON the ignition, with the engine OFF. Measure the voltage of the A/C Cut-out Control circuit at terminal No. 3 of the A/C compressor control module with a DMM. Does the voltage equal battery voltage? If yes, go to step  23 . If no, go to next step.
  18. The A/C compressor control module is malfunctioning. Inspect the A/C compressor control module and circuitry for a fault. Repair as necessary. After repairs, go to step  26 .
  19. Turn ON the ignition, with the engine OFF. Access the PCM electrical connector C3. Backprobe the Electrical Load Idle-up signal of the defogger circuit at the PCM connector with a test lamp connected to ground. Turn ON the rear defogger switch. Does the test lamp illuminate? If yes, go to step  23 . If no, go to next step.
  20. Turn OFF the ignition. Disconnect the PCM electrical connector C3. Check the Electrical Load Idle-up Defogger circuit for an open or a short between junction block 2 and the PCM. Repair as necessary. Was a repair necessary? If yes, go to step  26 . If no, diagnose and repair defogger circuit.
  21. Turn ON the ignition, with the engine OFF. Access the PCM electrical connector C3. Backprobe the Electrical Load Idle-up signal of the taillight circuit at the PCM connector with a test lamp connected to ground. Turn ON the parking lamp switch. Does the test lamp illuminate? If yes, go to step  23 . If no, go to next step.
  22. Turn OFF the ignition. Disconnect the PCM electrical connector C3. Check the Electrical Load Idle-up Taillights circuit for an open or a short between junction block 2 and the PCM. Repair as necessary. Was a repair necessary? If yes, go to step  26 . If no, diagnose and lighting system.
  23. Check for a short to ground in the Diagnostic Request circuit from the PCM connector C3 to the TE1 terminal of the underhood diagnostic link connector. Repair as necessary. Was a repair necessary? If yes, go to step  26 . If no, go to step  25 .
  24. Replace the PSP switch. After repairs, go to step  26 .
  25. Replace PCM. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE under PROGRAMMING in appropriate SELF-DIAGNOSTICS article. After replacing PCM, go to next step.
  26. Perform the scan tool Clear DTC Information function and road test the vehicle. Does the system now operate properly? If yes, system is okay. If no, see DIAGNOSTIC AIDS  .
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