P0031 - HO2S Heater Control Circuit Low (Bank 1 Sensor 1)
The heater circuit on a heated Oxygen / Lambda sensor is used to provide the heat required for correct sensor operation after cold start and also to maintain a consistent temperature during certain running conditions.The heater circuit supply voltage can either be directly supplied from the ECM or it can be supplied via a relay, this would usually be the main system relay. The heater earth circuit will normally be controlled directly by the ECM
Fault Code Explained
This fault code indicates that the ECM has detected Voltage in the circuit that is lower than expected or at zero. It is most likely that this will be caused by an open circuit, a short to earth or no supply Voltage
Different sensor types and wiring configurations are possible and it is recommended to refer to the manufacturers wiring diagram.
Test should include
- Testing heater circuit supply Voltage
- Heater circuit earth