P0135: Oxygen sensor heater circuit (bank 1, sensor 1)

What does it mean?

System

Powertrain (engine and transmission)

Subsystem

Fuel and air metering (sensors)

Type of code

Generic code: means the same on every make.

How urgent?

No immediate danger, but have it checked at the next opportunity: fuel use and emissions can rise, and the car can fail its inspection.

Possible causes

• Worn oxygen sensor (normal after 100,000 to 150,000 km)
• Sensor heater circuit or fuse
• Exhaust leak ahead of the sensor
• Burnt or corroded wiring or connector

Tip: don’t just clear the code. Clearing a code doesn’t fix the cause. It often comes back, and the stored data that helps us find the cause is then gone.