DTC 2-1-2 Front Heated Oxygen Sensor Signal

2-1-2 FRONT HEATED OXYGEN SENSOR SIGNAL

Preconditions for DTC
^ One of the preconditions for fuel trim to begin is that the Front Heated Oxygen Sensor (HO2S) must be ready to regulate, i.e. it should be at operational temperature and have the correct output voltage. Monitoring of the HO2S begins about 3 minutes after HO2S preheating starts. If there is a fault with the front or rear HO2S or their leads, so that the output voltage from the front HO2S deviates from the permitted value, DTC 2-1-2 will be set.

Substitute values
^ Fuel trim is inhibited.
^ Three-Way Converter (TWC) diagnosis inhibited.

Fault sources
^ Signal too high:
- Signal lead (+) short circuited to voltage supply.
- Signal lead (-) short circuited to voltage supply.
- Defective front HO2S.
- Defective rear HO2S.

^ Signal too low:
- Signal lead (+) short circuited to ground.
- Signal lead (-) short circuited to ground.
- Defective front HO2S.

^ Signal absent:
- Break in signal lead (-).
- Signal lead (+) short circuited to ground.
- Signal lead (-) short circuited to ground.
- Defective front HO2S.
- Defective rear HO2S.

^ Faulty signal:
- Signal lead (+) short circuited to signal lead (-).
- Defective front HO2S.

Fault symptoms
^ None.