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

What this code generally means, its most common causes, and how serious it is.

TYPE: GENERICSYSTEM: OXYGEN SENSORS

What does the code P0135 mean?

The oxygen sensor has a small internal heater that helps it reach operating temperature quickly after startup, instead of waiting on exhaust heat alone. This code flags a problem specifically in that heater circuit, not in the measurement itself.

Common possible causes

A burned-out internal heater element — the most common cause, tied to the sensor's age.
A blown heater-circuit fuse — cuts power to the heater without affecting the rest.
Corroded wiring or connector — poor contact specifically on this circuit.

General severity

Generally minor — not urgent

This code has almost no noticeable effect on everyday driving. Its main impact is that the sensor takes longer to give reliable readings after a cold start, especially in winter.

This is still a general severity for this code, not a diagnostic for your car. Only a real read of your codes, with your mileage and vehicle history, can tell what's really going on.

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Meca doesn't replace an in-person check by a professional. For any serious sign (a flashing light, a major loss of power, a fuel smell), see a mechanic promptly.

Frequently asked questions

Does Quebec's cold weather make this worse?

Indirectly, yes — without a working heater, the sensor takes even longer to reach useful temperature in cold weather, extending the period where mixture accuracy is reduced after startup.

Should I worry about safety?

No, this isn't a safety issue. It's mostly about mixture accuracy and emissions right after startup.

Is this the same sensor as P0133?

It can be the same sensor (bank 1, sensor 1), but P0135 is about its heater circuit, while P0133 is about how fast it responds with a measurement.