P0031: Oxygen sensor heater circuit low (bank 1, sensor 1)
The ECU sees too low a voltage in the heater of the front oxygen sensor on bank 1; usually the sensor, a wire or the fuse.
| Code | P0031 |
|---|---|
| System | Engine and transmission |
| Group | P00xx, Air, fuel and emissions |
| Type | Generic: it means the same on every make |
| Can you keep driving? | Yes, no rush |
What P0031 means
An oxygen sensor (lambda sensor) only reads accurately when very hot, so it has a built-in heater that warms it up as soon as the engine starts. The ECU sees a lower voltage than normal in that circuit, nearly always from an electrical fault: a broken heater element, a wire, the connector or the fuse. This sensor sits before the catalytic converter on bank 1 and measures the mixture so the ECU can adjust fuelling.
Most common causes
- Blown heater fuse
- Loose or corroded sensor connector
- Open heater element in the sensor
- Wire cut or shorted to earth by rubbing on the exhaust
- Fault in the ECU’s control circuit (uncommon)
Symptoms
- Engine warning light on
- Slightly higher fuel consumption, especially on short trips
- Higher emissions that can fail an inspection
Can you drive with P0031?
Yes, no rush You can drive normally; the engine runs fine, although it may use a little more fuel when cold. Get it fixed before the next inspection.
Open the bonnetthe in-depth explanation
How to check it
Start by checking the oxygen sensor heater fuse in the fuse box. With the engine cold and the sensor unplugged, a multimeter across the two heater terminals should show a low resistance; if it reads nothing, the sensor has failed.
How to read and clear P0031 with Final OBD
Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P0031 with its description and whether it’s confirmed, pending or permanent.
If the engine stores it over standard OBD, with FREE you read this code with its explanation for nothing and clear it. With PRO you also read the faults of every control unit and clear them in all of them.
Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before an inspection. It’s all in how to read and clear fault codes and in inspections and OBD.
Similar codes
- P002D The exhaust camshaft profile control B circuit on bank 2 is open
- P002E Low signal in the variable profile control of camshaft B on the second bank
- P002F The exhaust camshaft profile control B circuit on bank 2 reads high
- P0030 Oxygen sensor heater circuit fault (bank 1, sensor 1)
- P0032 Oxygen sensor heater circuit high (bank 1, sensor 1)
- P0033 The turbo A discharge valve control has an electrical fault
- P0034 The turbo A discharge valve control gives a lower signal than normal
- P0035 The turbo A discharge valve control gives a higher signal than normal
- P0010 Camshaft A actuator control: open circuit (bank 1)
- P0011 Camshaft A timing over-advanced (bank 1)
- P0012 Camshaft A timing over-retarded (bank 1)
- P0013 Camshaft B actuator control: open circuit (bank 1)
What does code P0031 mean?
An oxygen sensor (lambda sensor) only reads accurately when very hot, so it has a built-in heater that warms it up as soon as the engine starts. The ECU sees a lower voltage than normal in that circuit, nearly always from an electrical fault: a broken heater element, a wire, the connector or the fuse. This sensor sits before the catalytic converter on bank 1 and measures the mixture so the ECU can adjust fuelling.
Can you drive with P0031?
You can drive normally; the engine runs fine, although it may use a little more fuel when cold. Get it fixed before the next inspection.
How do you clear P0031?
With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, P0031 comes back.
Read it on your car
Final OBD reads and clears engine faults through standard OBD for free, each one explained in plain English. With PRO it also reads the faults of every control unit, each make’s own codes included, and clears them in all of them.
