Diagnostic Procedure

DIAGNOSTIC PROCEDURE

HINT: If diagnostic trouble code "21" is output, check the left bank main oxygen sensor circuit. If diagnostic trouble code "28" is output, check the right bank main oxygen sensor circuit.

1. Check voltage of terminals HTL1, HTR1.
- If OK proceed to step 3.
- If not OK proceed to step 2.
2. Check resistance of main heated oxygen sensor heater.
- If OK check and repair main heated oxygen sensor heater circuit.
- If not OK replace main heated oxygen sensor.
3. Check operation of main heated oxygen sensor sensor heater.
- If OK replace main heated oxygen sensor.
- If not OK check and replace engine control module.