P0155

P0155

O2 Sensor Heater, Function

NOTE: The function checks the sensor temperature (by measuring the internal resistance of the Nernst cell) depending on the exhaust temperature. This can be used to discover discrepancies between the set point and actual temperature of the O2 sensor, from which a faulty heating control can be deduced.
If the DME has detected a vehicle voltage > 16 V, fuel trim is also interrupted.

Diagnostic conditions
- DME control unit power supply voltage (DME) 10 V ... 16 V
- Exhaust temperature 300 degrees C (572 degrees F) ... 600 degrees C (1,112 degrees F)
- Time after engine starts > 200 s
- Intake air temperature > -7 degrees C (19 degrees F)
- No overrun
- No other driver fault of O2 sensor heater

Possible fault causes
- Vehicle voltage > 16 V
- Connector corrosion
- Contact resistance in the lines
- O2 sensor faulty
- DME control unit faulty