Powertrain
generic / SAE
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.
SystemPowertrain
Typegeneric / SAE
GroupP0
Range / number1 / 35
Possible causes
- Heater element open-circuit high
- Heater fuse blown medium
- Wiring fault to heater low
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)
Inspection / repair
- Difficulty: easy
- DIY: possible
- Estimated cost: 60–250 €
- Estimated time: 0.3–1.5 h
- Component: oxygen sensor upstream
- Component: oxygen sensor heater relay
- Component: oxygen sensor heater fuse
- MIL / check engine light
- emissions-relevant
- drive cycle required
Sources
References
sae:J2012