Diagnosis & Repair
- Connect scan tool to DLC No. 3 connector. See Figure. Start vehicle and warm engine to normal operating temperature. Using scan tool, monitor sensor No. 1. Snap accelerate engine 3 times. Sensor should indicate a rich signal (.45 volt or more) at least once.
- If a rich signal is indicated at least once, replace ECM and retest. If sensor does not display a rich signal at least once, check for open or short circuit in wiring harness between ECM and oxygen sensor. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair wiring as necessary. If wiring harness is okay, replace oxygen sensor and retest.