P25BFAlternative Fuel Disable Control Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P25BF flags a voltage on the alternative fuel disable output that is too high for the state the engine controller is commanding. On a low-side driver this usually means a short to battery or ignition voltage, for instance where a gas kit harness has been routed along a hot feed or tapped into the wrong wire. Depending on design, a constantly high line may be read by the gas system as a permanent block, or the controller may switch the driver off to protect itself; either way the command it sends is no longer trustworthy. GM's 2016 Silverado and Sierra bi-fuel trucks show what the driver sees when gas operation is refused: the fuel indicator flashes and the truck stays on gasoline. No manufacturer documents P25BF publicly. Note that SAE lists High before Low in this group.
- What you may notice
- Gas operation blocked, vehicle runs on gasoline only
- Fuel mode indicator flashes
- Check engine lamp
- Likely causes
- LikelyControl wire shorted to battery or ignition voltage
- PossibleRetrofit gas kit tapped into the wrong circuit
- RareFaulty input stage in the gas controller backfeeding voltage
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €80 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.