P0030HO2S Heater Control Circuit (Bank 1 Sensor 1)
- 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 upstream oxygen sensor on bank 1 (sensor 1, before the catalytic converter) only delivers a usable signal once its ceramic element is hot. A heating element inside the sensor gets it there quickly after a cold start. Typically the heater receives battery voltage via a fuse or relay, and the engine control module switches the ground side with a pulsed signal while comparing the commanded state with the measured voltage or current. P0030 is the general circuit fault: the measured state does not fit the command, most often because the circuit is interrupted. Which physical fault sets P0030, P0031 or P0032 is defined by each manufacturer. Without heating, closed-loop mixture control starts late and cold-start emissions rise.
- What you may notice
- Check engine light on
- Usually no noticeable drivability problem
- Closed-loop control starts late after a cold start
- Emissions test or readiness check failed
- Likely causes
- LikelyHeater circuit interrupted, e.g. broken or chafed wire near the exhaust
- LikelyHeating element inside the sensor burnt out
- PossibleConnector corroded or terminal pushed back
- PossibleHeater supply fuse or relay faulty
- RareOutput driver in the engine control module faulty
- 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.