Powertrain
generic / SAE
P0155
O2 Sensor Heater Circuit Malfunction (Bank 2, Sensor 1)
Same condition as P0135 but on the upstream sensor of bank 2. The sensor heater warms the element to operating temperature (~600 °C); without it the lambda sensor stays inactive in closed loop and the ECM cannot trim mixture.
SystemPowertrain
Typegeneric / SAE
GroupP0
Range / number1 / 55
Possible causes
- Heater element open-circuit high
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
- MIL / check engine light
- emissions-relevant
- drive cycle required
Sources
References
sae:J2012