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Home >> Chevrolet >> 2001 >> Prizm Base, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System & Component Testing >> Circuit Tests >> Electrical Load Idle-Up Circuit (PRIZM) >> Diagnostic Procedure

Diagnostic Procedure

NOTE: Before proceeding with this test, ensure rear defogger and parking lights operate properly.
  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article. After performing OBD system check, go to next step.
  2. Install scan tool. Start and warm engine to normal operating temperature. Turn off all accessories. Monitor Idle Air Control valve (IAC) duty cycle while turning rear window defogger on and off. Duty cycle should increase between 1-3 percent. If IAC duty cycle increases when defogger switch is turned on, go to next step. If IAC duty cycle does not increase, go to step  19.
  3. Monitor IAC duty cycle while turning parking lights on and off. Duty cycle should increase between 1-3 percent. If IAC duty cycle increases when switch is turned on, go to next step. If IAC duty cycle does not increase, go to step  21.
  4. Install scan tool. Start and warm engine to normal operating temperature. Turn off all accessories. Monitor IAC duty cycle. Turn A/C switch to ON position and blower speed selector switch to any position except OFF. Duty cycle should increase between 4-14 percent. If IAC duty cycle increases when A/C switch is turned to ON position, go to next step. If IAC duty cycle does not increase, go to step  10.
  5. Install scan tool. Start and warm engine to normal operating temperature. Turn off all accessories. Monitor IAC duty cycle. Turn steering wheel to right and left. Return steering wheel to center, straight ahead position. Duty cycle should increase between 2-10 percent when steering wheel was turned fully in either direction. If IAC duty cycle increases when switch is turned on, system is okay. If IAC duty cycle does not increase, go to next step.
  6. Turn ignition on, engine off. Disconnect Power Steering Pressure (PSP) switch connector. Measure voltage between PSP switch connector and ground. See WIRING DIAGRAMS article. If battery voltage exists, go to next step. If battery voltage goes not exist, go to step  8.
  7. Connect a test light to battery voltage. Probe PSP switch connector (switch side) with test light. Start engine. Observe test light while turning steering wheel to right and left. If test light illuminates when steering wheel is turned, go to step  23. If test light does not illuminate when steering wheel is turned, go to step  9.
  8. Check for open or short to ground in PSP switch circuit between PCM and PSP switch. Repair as necessary. After repairs, go to step  26. If circuit is okay, go to step  25.
  9. Check for poor ground connection at power steering pump. Repair as necessary. After repairs, go to step  26. If circuit is okay, go to step  24.
  10. Start engine. Turn A/C on. Using DVOM, backprobe A/C ON circuit at PCM connector C4 terminal No. 18 (Yellow/Red wire on 4-speed A/T) or PCM connector C3 terminal No. 10 (Yellow/Red wire on M/T and 3-speed A/T) and ground. Measure voltage. If voltage is 0-1 volt, go to step  11. If voltage is not 0-1 volt, go to step  13.
  11. Start engine. Turn A/C off. Using DVOM, backprobe A/C ON circuit at PCM connector C4 terminal No. 18 (Yellow/Red wire on 4-speed A/T) or PCM connector C3 terminal No. 10 (Yellow/Red wire on M/T and 3-speed A/T) and ground. Measure voltage. If battery voltage exists, go to step 14. If battery voltage does not exist, go to next step.
  12. Turn ignition off. Disconnect PCM connector. Back-out A/C ON Signal wire from PCM connector C4 terminal No. 18 (Yellow/Red wire on 4-speed A/T) or PCM connector C3 terminal No. 10 (Yellow/Red wire on M/T and 3-speed A/T). Reconnect PCM connector. Turn ignition on, engine off. Using DVOM, backprobe A/C ON circuit through empty slot in PCM connector and ground. If battery voltage exists, go to next step. If battery voltage does not exist, go to step  25.
  13. Check for open or short in A/C ON circuit between PCM connector C4 terminal No. 18 (Yellow/Red wire on 4-speed A/T) or PCM connector C3 terminal No. 10 (Yellow/Red wire on M/T and 3-speed A/T) and A/C compressor control module. See appropriate MANUAL A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING. Repair as necessary. After repairs, go to step  26. If circuit is okay, go to step  18.
  14. Start engine. Turn A/C off. Using DVOM, backprobe A/C CUTOUT CONTROL circuit at PCM connector C4 terminal No. 12 (Red/Blue wire on 4-speed A/T) or PCM connector C3 terminal No. 21 (Red/Blue wire on M/T and 3-speed A/T) and ground. Measure voltage. If no voltage is present, go to next step. If voltage is present, go to step  25.
  15. Start engine. Turn A/C on. Using DVOM, backprobe A/C CUTOUT CONTROL circuit at PCM connector C4 terminal No. 12 (Red/Blue wire on 4-speed A/T) or PCM connector C3 terminal No. 21 (Red/Blue wire on M/T and 3-speed A/T) and ground. Measure voltage. If battery voltage exists, go to DIAGNOSTIC AIDS . If battery voltage does not exist, go to next step.
  16. Check for open or short to ground in A/C CUTOUT circuit between PCM connector C4 terminal No. 12 (Red/Blue wire on 4-speed A/T) or PCM connector C3 terminal No. 21 (Red/Blue wire on M/T and 3-speed A/T) and A/C compressor control module. Repair as necessary. After repairs, go to step  26. If circuit is okay, go to next step.
  17. Disconnect A/C compressor control module connector. Turn ignition on, engine off. Measure voltage between A/C compressor control module connector terminal No. 3 (Red/Blue wire) and ground. If battery voltage exists, go to step  23. If battery voltage does not exist, go to next step.
  18. A/C compressor control module is malfunctioning. Inspect A/C compressor control module and circuits for fault. See appropriate MANUAL A/C-HEATER SYSTEMS article in AIR CONDITIONING & HEATING. Repair as necessary. After repairs, go to step  26.
  19. Turn ignition on, engine off. Using test light connected to ground, backprobe IDLE-UP circuit (defogger) at PCM connector C3 terminal No. 10 (Black wire on 4-speed A/T) or PCM connector C3 terminal No. 3 (Black wire on M/T and 3-speed A/T). Turn rear defogger switch to On position. If test light illuminates, go to step  23. If test light does not illuminate, go to next step.
  20. Turn ignition off. Disconnect PCM connector C3. Check for open or short in IDLE-UP circuit (defogger) between PCM connector C3 terminal No. 10 (Black wire on 4-speed A/T) or PCM connector C3 terminal No. 3 (Black wire on M/T and 3-speed A/T) and junction block 2. See appropriate REAR WINDOW DEFOGGERS article in ACCESSORIES & EQUIPMENT. Repair as necessary. After repairs, go to step  26. If circuit is okay, check and repair rear window defogger system as necessary.
  21. Turn ignition on, engine off. Using test light connected to ground, backprobe IDLE-UP circuit (taillight) at PCM connector C3 terminal No. 3 (Green wire on M/T and 3-speed A/T) or PCM connector C3 terminal No. 20 (Green wire on 4-speed A/T). Turn parking lamp switch to ON position. If test light illuminates, go to step  23. If test light does not illuminate, go to next step.
  22. Turn ignition off. Disconnect PCM connector C3. Check for open or short in IDLE-UP circuit (taillight) between PCM connector C3 terminal No. 3 (Green wire on M/T and 3-speed A/T) or PCM connector C3 terminal No. 20 (Green wire on 4-speed A/T) and junction block No. 2. See EXTERIOR LIGHTS in ACCESSORIES & EQUIPMENT.
  23. Check for short to ground in the DIAGNOSTIC REQUEST circuit from the PCM connector C3 terminal No. 5 (Blue/White wire on 4-speed A/T) or PCM connector C3 terminal No. 6 (Blue/White wire on M/T and 3-speed A/T) and TE1 terminal of underhood DLC. Repair as necessary. After repairs, go to step  26. If circuit is okay, go to step  25.
  24. Replace PSP switch. After repairs, go to step  26.
  25. Replace PCM. After repairs, go to next step.
  26. After repairs are completed, operate vehicle within conditions under which original symptom was observed. If system operates properly, repair is complete. If system does not operate properly, see DIAGNOSTIC AIDS .
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