O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)
The oxygen sensor measures oxygen in the exhaust gas and has to be very hot to work, so it has a heating element. This code means a fault in that heater circuit on the rear sensor, after the catalytic converter (bank 1, sensor 2).
What the car has detected
The engine computer monitors the current drawn by the sensor heater and has seen a value too high or too low, or an open circuit.
The car usually drives the same. It may use a little more fuel and take longer to set the mixture correctly when cold, and it may fail the emissions inspection. It can wait, but it should be repaired.
Symptoms
- Engine warning light on
- Slightly higher fuel consumption
- Slower mixture control with a cold engine
- Usually no change when driving
Possible causes
- Failed sensor heating element (the most common cause)
- Blown heater fuse
- Damaged wiring or a corroded or melted connector near the exhaust
- Open control circuit or, less often, a fault in the engine computer
Checks for the garage
- Check the heater fuse; if it blows again, suspect the sensor
- Inspect the connector and wiring for corrosion, melted pins or contact with the exhaust
- Measure the heater resistance and compare it with the specification
- Check that power arrives with the ignition on and that the engine computer switches the control on
- Replace the sensor if the fuse and wiring are fine and the resistance is wrong
Next step
Have the sensor heater fuse, its wiring and the sensor's resistance checked before replacing the sensor.
If the fuse is fine, the garage needs to measure the circuit and the sensor. It is not urgent, but repair it before the next inspection.