Chart A9 - Oxygen Sensor Diagnosis
NOTE:
Test numbers refer to test numbers on diagnostic chart.
- With engine running warm (coolant temperature 185°F/85°C or greater) and at fast idle, observe engine data code ED07.
- While running engine at fast idle, observe open/closed loop status light, and "AUTO" indicator light in CCDIC. If ECM switches system to closed loop operation, the oxygen sensor is okay. If ECM remains in open loop operation, coolant temperature code ED04 is above 185°F (85°C), and ECM and harness are operating properly as verified by CHART A6 - OXYGEN SENSOR NOT READY, replace oxygen sensor.
- If voltage remains between .30-.60 volts for a minimum of one minute, check for the possibility of leaded or contaminated fuel before checking for a faulty oxygen sensor connection or a faulty oxygen sensor, as leaded fuel can damage catalytic converter and oxygen sensor.
- If there is no voltage variation and if ECM and harness are operating properly as verified by CHART A6, check for faulty oxygen sensor.
NOTE:
This chart assumes that "DFI System Check" and chart A-6 "Open Loop Diagnosis" have both been performed to verify that the ECM and oxygen sensor wiring are operating properly.