HO2S Heater Control Circuit Low (Bank 1 Sensor 1)
O2 sensor heater control circuit on bank 1, sensor 1 reports low voltage. Likely shorted to ground or open in the heater control wire. The heater warms the sensor element to operating temperature (~600 °C); without it the sensor stays inactive in closed loop and the ECM cannot trim mixture.
Affected components
- Oxygen sensor heater
- Sensor wiring
Common causes
- High likelihood: Heater control wire shorted to ground
- Medium likelihood: Heater element internally shorted
- Low likelihood: Connector pins corroded - high contact resistance
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.