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, perform A-4: ENGINE SYSTEM CHECK under SYSTEM TESTS, then go to next step.
- Start engine and allow it to reach normal operating temperature. Race engine speed up to 2000 RPM for 60 seconds. While revving engine 5 or 6 times, observe on scan tool HO2S-1 values. If HO2S-1 voltage does not deflect from below 0.3 volt to over 0.6 volt, go to next step. If HO2S-1 voltage deflect from below 0.3 volt to over 0.6 volt, go to step 4 .
- Turn ignition switch to LOCK position. Disconnect HO2S-1 4-pin harness connector C13, located between exhaust manifold and front catalytic converter. See Figure . Start engine and allow it to reach normal operating temperature. Race engine speed up to 2000 RPM for 60 seconds. While revving engine 5 or 6 times, measure voltage between HO2S-1 pigtail connector terminals No. 1 and 2 (component side). See Fig 1 . If HO2S-1 voltage does not deflect from below 0.3 volt to over 0.6 volt, replace HO2S-1. See HEATED OXYGEN SENSORS NO. 1 & 2 under ENGINE SENSORS & SWITCHES in REMOVAL & INSTALLATION article. If HO2S-1 voltage does deflect from below 0.3 volt to over 0.6 volt, check for open or short circuit in Red wire and Gray/Yellow wire between ECM and HO2S-1. If open or short circuit is found, repair as necessary. After repair, repeat DTC CONFIRMATION TEST . If open or short circuit is not found, substitute ECM with a known good unit and repeat DTC CONFIRMATION TEST .
- Race engine speed up to 2000 RPM for 60 seconds. Allow engine to idle. Using scan tool, check short term fuel trim value. If value is between -20 and +20 percent, problem is intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article. If value is not between -20 and +20 percent, perform diagnose and repair procedure for DTC P0171 OR DTC P0172 . After repair, repeat DTC CONFIRMATION TEST .