Parts
$30–200
P0135 — O2 Sensor Heater Circuit (Bank 1, Sensor 1)
CAUTIONIs it safe to drive? The heater inside the front O2 sensor isn't working. Driveable; the sensor warms slowly so cold-start economy and emissions suffer.
What P0135 means
Modern O2 sensors have an internal heater so they work right away. This code says that heater circuit is open or out of range — usually the sensor itself or its fuse/wiring.
Most likely causes (in order)
- Failed O2 sensor heater element (replace the sensor)
- Blown heater fuse
- Wiring / connector to the sensor heater
Symptoms you might notice
- Check-engine light
- Slightly worse cold economy
What to check first
Check the heater fuse and the sensor's heater resistance; if power/ground/fuse are good, the sensor is bad.
Repair cost & difficulty
Labor
0.5–1.5 hr
Difficulty
DIY-friendly