DTC 5-2-1 Front Heated Oxygen Sensor Preheating

5-2-1 FRONT HEATED OXYGEN SENSOR, PREHEATING

Preconditions for DTC
^ Monitoring of the Heated Oxygen Sensor (HO2S) heating circuit begins approx. 3 minutes after the HO2S preheating sequence starts.
^ If the ECM registers excessive or insufficient current in the heating circuit, DTC 5-2-1 or 5-2-2 will be set.

Substitute value
^ Fuel trim is inhibited.

Fault sources
^ Signal too high:
- Signal lead short circuited to voltage supply.
- Defective HO2S.

^ Signal too low:
- Signal lead short circuited to ground.
- Break in signal or voltage lead.
- Contact resistance in connectors.
- Defective HO2S.

Fault symptoms
^ None.