P01F7O2 Sensor Signal Biased/Stuck Rich Bank 1 Sensor 4
- 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
- Sensor 4 on bank 1 is a fourth oxygen sensor, downstream of a further converter. No manufacturer or vehicle using sensor 4 codes could be identified (GM and Ford documents stop at sensor 3); the description follows CARB's requirements for downstream sensors and GM's checks on sensor 2. P01F7 means the sensor stays rich: when the module leans the mixture or cuts fuel on overrun, the signal does not drop into the lean range. CARB names exactly this rich-to-lean transition during fuel cut-off as the minimum check for downstream sensors; GM tests sensor 2 this way as a two-trip fault. Usual causes are a sooted or oil-fouled sensor or a signal wire shorted to the heater supply.
- What you may notice
- Check engine light on (usually after two drive cycles)
- Catalyst monitor readiness possibly not set
- Usually no change in driving
- Likely causes
- LikelySensor sooted, oil-fouled or aged
- PossibleSignal wire shorted to voltage (e.g. heater supply)
- RareMixture genuinely rich (leaking injector, coolant or oil burning)
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Easy · Often possible to do yourself.Typical cost: €60 – €300
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.