Diagnosis & Repair Procedure
NOTE:
For better performance and results of this diagnostic procedure, usage of appropriate wiring diagram is recommended. See ENGINE PERFORMANCE
in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
NOTE:
Perform all voltage and resistance tests using a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure. Use an ohmmeter to isolate wiring harness shorts or opens.
- If engine system check has been performed, go to next step. If engine system check has not been performed, see and perform A-4: ENGINE SYSTEM CHECK under SYSTEM TESTS and go to next step.
- Turn ignition switch to LOCK position. Disconnect HO2S-1 4-pin harness connector C13, located before warm-up three way catalytic converter. Measure resistance between HO2S-1 harness connector terminals No. 3 and 4 (component side). See Fig 1 . If resistance is 4.5-5.7 ohms, go to next step. If resistance is not 4.5-5.7 ohms, replace HO2S-1. See HEATED OXYGEN SENSOR NO. 1 & 2 under ENGINE SENSORS & SWITCHES in REMOVAL, OVERHAUL & INSTALLATION article. After repair, repeat DTC CONFIRMATION TEST .
- Locate ECM 30-pin harness connector C51-2 under instrument panel, behind glove box. Turn ignition switch to ON position. Backprobe and measure voltage between ground and ECM harness connector C51-2 terminal No. 4 (Gray wire). See Figure . If voltage is 10-14 volts, go to next step. If voltage is not 10-14 volts, check Black/White wire and Gray wire for open circuit or short to ground between ECM and HO2S-1. If open circuit or short to ground is found, repair as necessary and repeat DTC CONFIRMATION TEST . If open circuit or short to ground is not found, substitute ECM with a known good unit and repeat DTC CONFIRMATION TEST .
- Start engine. Allow engine to reach normal operating temperature and let it idle. Backprobe and measure voltage between ground and ECM harness connector C51-2 terminal No. 4 (Gray wire). See Figure . If voltage is 0-1 volt, problem is intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article. After repair, repeat DTC CONFIRMATION TEST . If voltage is not 0-1 volt, check HO2S-1 connector terminals for corrosion or poor connection. If connector terminals are faulty, repair as necessary and repeat DTC CONFIRMATION TEST . If connector terminals are okay, substitute ECM with a known good unit and repeat DTC CONFIRMATION TEST .