OXYGEN SENSOR HEATER CIRCUIT FAILURE

Our first fault presents itself with a vehicle that will run fine, but a warning light will be triggered. Carrying out a basic fault code check, even using a lowcost EOBD reader, will show the fault code ‘P0030 heater oxygen sensor heater circuit bank 1 circuit malfunction’.

Essentially the ECU is sensing a fault in the heater, which lies within the oxygen sensor heater circuit line.

The oxygen sensor is located directly in the exhaust manifold with a four-pin plug connector. Simply disconnect the connector and, with your multimeter set to 'ohms', connect against the two grey wires. You will likely see no reading, which indicates an internal open circuit within the sensor.

Replacement of the sensor requires either a special socket or spanner. It’s worth either running the engine for a while to warm things up or else applying a suitable penetrating fluid to aid removal. Sometimes the threads in the manifold will strip when removing the sensor. To overcome this problem you can try cleaning the threads with a suitable tap or employing a thread insert such as a Helicoil.

We recommend fitting good quality replacement sensors because cheaper items don’t last as long.