O2 Sensor Heater Control Circuit Low Bank 1 Sensor 2
The ECU detects a low-side voltage below threshold on the heater control of the rear oxygen sensor on bank 1. The heater driver may be stuck on or shorted to ground.
Affected components
- Oxygen sensor
- Oxygen sensor heater circuit
Common causes
- High likelihood: Heater wire shorted to ground
- Medium likelihood: Internal heater short
- Low likelihood: Connector pins corroded - high contact resistance
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
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.