Inspection Procedure
INSPECTION PROCEDUREHINT: Diagnostic trouble code 21 is for the left bank main heated oxygen sensor circuit. Diagnostic trouble code 28 is for the right bank main heated oxygen sensor circuit.
1. Disconnect the ECM connector, check voltage between terminals HTL1, HTR1 of engine control module connector and body ground.
- Connect the Check Harness A.
- Disconnect engine control module connector.
- Turn ignition switch on.
- Measure voltage between terminals HTL1, HTR1 of engine control module connector and body ground.
Voltage: 9 - 14 volts
- If OK proceed to step 3.
- If not OK proceed to step 2.
2. Check main heated oxygen sensor heater.
- Disconnect main heated oxygen sensor connector.
- Measure resistance between terminals 1 and 2 of main heated oxygen sensor connector.
Resistance: 5.1 - 6.3 ohms at 2O°C (68°F)
- If OK Check and repair harness or connector between main relay and main heated oxygen sensor, main heated oxygen sensor and engine control module.
- If not OK replace main heated oxygen sensor.
3. Check voltage between terminals HTL1, HTR1 of engine control module connector and body ground.
- Connect engine control module connector.
- Warm up engine to normal operating temperature.
Idling: 0 volts
4,000 rpm: 9 - 14 volts
NOTE: In the 4,000 rpm racing check, continue engine racing at 4,000 rpm for approximately 20 seconds or more.
- If OK replace main heated oxygen sensor.
- If not OK check and replace engine control module.