P0038HO2S Heater Control Circuit High (Bank 1 Sensor 2)
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- The heated oxygen sensor on bank 1 is the downstream sensor 2 behind the (first) catalytic converter, used mainly to monitor the converter. Its heating element brings it quickly to operating temperature. Typically the heater receives battery voltage via a fuse, and the engine control module switches the ground side with a pulsed signal while checking that the circuit state matches the command. P0038 means the control module sees too high a voltage in the heater control circuit, typically because the switched ground wire is shorted to battery voltage. Which physical fault sets the general, low or high code is defined by each manufacturer. Without heating, the sensor becomes ready late and catalyst monitoring may not complete.
- What you may notice
- Check engine light on
- Usually no noticeable drivability problem
- Catalyst monitor does not complete
- Emissions test or readiness check failed
- Likely causes
- LikelyHeater control wire shorted to battery voltage, e.g. chafed harness
- PossibleHeating element shorted internally
- PossibleWater in the connector causing leakage between pins
- RareOutput driver or software of the engine control module
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €80 – €350
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.