O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 2)
The heating element inside the downstream oxygen sensor on bank 1 is open-circuit, drawing no current, or drawing too much. Without heater, the sensor takes much longer to reach operating temperature, delaying catalyst diagnosis.
Affected components
- Oxygen sensor downstream
- Oxygen sensor heater relay
Common causes
- High likelihood: Heater element open-circuit
- Medium likelihood: Heater fuse blown
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.