Diagnosis & Repair
- Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in TESTS W/CODES - 1.0L article. After performing OBD system check, go to next step.
- Install scan tool. Start and warm engine to normal operating temperature. Turn off all accessories. Using scan tool, monitor electrical load parameter while turning parking lights, rear window defogger, and blower motor on and off. If scan tool does not indicate on when accessories are turned on and off when accessories are turned off, go to next step. If scan tool indicates accessories on and off as specified, system is functioning normally.
- If engine RPM does not increase when at least one accessory is turned on, go to next step. If engine RPM does increase, go to step 7).
- Turn ignition off. Disconnect PCM electrical connectors. Turn ignition on with engine off. Using a test light connected to ground, probe PCM connector electrical load idle-up signal circuit. See WIRING DIAGRAMS - 1.0L article. Turn headlight switch to Park or Head position. If test light illuminates, go to next step. If test light does not illuminate, go to step 6).
- Check for poor terminal connections at PCM. Repair as necessary. After repairs, go to step 10). If connections are okay, go to step 9).
- Check for an open in electrical load idle-up signal circuit between diode module and PCM. Repair as necessary. After repairs, go to step 10). If circuit is okay, go to step 8).
- Check components and circuits in related systems which did not increase engine RPM:
- Faulty blower motor speed selector switch, poor connection or an open in blower motor speed selector switch circuit to diode module.
- Faulty headlight switch, poor connection or an open in headlight switch circuit to diode module.
- Faulty rear defogger switch, poor connection or an open in rear defogger switch circuit to diode module.
Repair as necessary. After repairs, go to step 10). If no repairs were necessary, go to next step.
- Replace diode module. After repairs, go to step 10).
- Replace PCM. After repairs, go to next step.
- 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, go to DIAGNOSTIC AIDS.