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.
Affected components
- Oxygen sensor upstream
- Oxygen sensor heater relay
Common causes
- High likelihood: Heater element open-circuit
Possible 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)
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
- A drive cycle may be required after repair
Related codes
Sources
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.