OBD-II code · Powertrain (generic)
P0135 O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1)
The heating element inside the upstream oxygen sensor draws no current, draws too much current, or is open-circuit. The heater brings the sensor to operating temperature so closed-loop control can start within seconds rather than minutes.
Is it safe to drive with P0135?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyHeater element open-circuit
- PossibleHeater fuse blown
- Less likelyWiring fault to heater
Symptoms
- Check engine light on after several drive cycles
- Slightly increased fuel consumption during cold start
- Delayed entry into closed-loop fuel control
- Failed emissions inspection (lambda readiness)
Repair at a glance
- Difficulty
- Easy
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.3–1.5 h
- Emissions test
- Likely to fail
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Oxygen Sensor Upstream, Oxygen Sensor Heater Relay, Oxygen Sensor Heater Fuse
Related codes
- P0141O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 2)
- P0155O2 Sensor Heater Circuit Malfunction (Bank 2, Sensor 1)
- P0161O2 Sensor Heater Circuit Malfunction (Bank 2, Sensor 2)
- P0132O2 Sensor Circuit High Voltage (Bank 1, Sensor 1)
- P0133O2 Sensor Slow Response (Bank 1, Sensor 1)
- P0134O2 Sensor Circuit No Activity / Slow Response (Bank 1 Sensor 1)
- P0136O2 Sensor Circuit Malfunction (Bank 1, Sensor 2)
- P0137O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2)
- P0138O2 Sensor Circuit High Voltage (Bank 1, Sensor 2)
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.