Oxygen sensor heater circuit

What it means

An oxygen sensor only works when it is very hot. A small electric heater inside it brings it up to temperature within seconds of a cold start. These codes mean the heater, its fuse or its wiring has failed. The sensor still works once the exhaust warms it, only later.

Codes in this group

Bank 1 is the side of the engine that has cylinder 1. Sensor 1 is before the catalytic converter and sensor 2 is after it. More terms explained.

What you may notice

• Usually only the warning light
• Slightly higher fuel use on short trips

Common causes

Most likely first:

• The heater element inside the sensor has burnt out (most common)
• A blown fuse for the heater circuit
• Damaged wiring or connector

What to check first

• Check the fuses listed for the oxygen sensor heaters in the owner's manual
• If the fuse is good, the sensor itself is the usual fix

Have a mechanic confirm. A fault code tells you which system reported a problem, not which part has failed. The same code can have several causes, and they differ between car models. Use this page to understand the code, then have a qualified mechanic test the car before any part is replaced.

After the repair

Once the cause is fixed, the code can be cleared with a scan tool, or the warning light goes out by itself after several trips without the fault. Clearing a code without fixing the cause only hides it for a while. More about clearing codes.

Related codes

Mass air flow (MAF) sensor (P0100), Manifold pressure (MAP) and barometric sensor (P0105), Intake air temperature sensor (P0110), Engine coolant temperature sensor (P0115), Thermostat and engine warm-up (P0125), Throttle position sensor (P0120), Accelerator pedal sensor and throttle agreement (P2120), Electronic throttle actuator (P2100). All codes.

Written in November 2026. These are generic OBD-II codes, the same on all makes. Causes and repair steps differ between models.