Chart A9 - Oxygen (O2) Sensor Diagnosis
NOTE:
Test numbers refer to test numbers on diagnostic chart.
- With engine running, coolant temperature 185°F (85°C) or greater, and at fast idle, observe engine data parameter 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 parameter ED04 is greater than 185°F (85°C), and ECM and harness are operating properly as verified by CHART A6, replace oxygen sensor.
- If voltage remains between .30-.60 volt 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.