MasterTuning Fault code dictionary (DTC)

P0135 — O2 sensor heater circuit (bank 1 sensor 1)

Severity: Warning Can you drive? Yes, no known limitation Make: All makes (OBD-II standard)
MeaningA lambda sensor must reach about 300°C to measure, and gets there with an internal heater. When that heater fails the sensor stays blind until the exhaust warms it up.
FamilyPowertrain (P)

Typical symptoms

Engine warning light on, often right after starting
Higher consumption in the first minutes
Rough cold idle
No symptoms once warm

Common causes

Open circuit in the sensor's internal heater: a wear item
Blown heater circuit fuse
Broken relay or wiring
Connector melted by exhaust heat

What to do

Measure the heater resistance across its two dedicated pins: an open circuit means the sensor is finished. Check the fuse first though, because when it blows the heater codes of every sensor appear together — and then the sensors are not at fault.

Frequently asked questions

What does code P0135 mean?

O2 sensor heater circuit (bank 1 sensor 1). A lambda sensor must reach about 300°C to measure, and gets there with an internal heater. When that heater fails the sensor stays blind until the exhaust warms it up.

Can I keep driving with code P0135 active?

Yes, no known limitation

Common causes — P0135

Open circuit in the sensor's internal heater: a wear item Blown heater circuit fuse Broken relay or wiring Connector melted by exhaust heat

How do you fix code P0135?

Measure the heater resistance across its two dedicated pins: an open circuit means the sensor is finished. Check the fuse first though, because when it blows the heater codes of every sensor appear together — and then the sensors are not at fault.

Need help with this fault?

We are ECU specialists: diagnosis, file repair and remapping for cars, bikes, trucks and agricultural vehicles.

Contact us
Where to get it fixed

Related codes