P25C2Alternative Fuel Disable Signal 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
- P25C2 means the alternative fuel disable signal arriving at the engine controller sits above its valid range. Likely explanations are a short to a voltage feed, a missing ground at the gas controller that lets its output float up, or an open line combined with an internal pull-up in the reading module. Whether a high level reads as blocked or as released depends on the design, so the engine controller can no longer trust the gas system's status and will usually stay with or return to gasoline. GM's Impala bi-fuel information shows the logic behind this: with a delivery concern on one side, the ECM moves to the fuel system that is working. No manufacturer documents P25C2 publicly. In the SAE list the High code precedes the Low code here, unlike most groups.
- What you may notice
- Vehicle stays on gasoline
- Gas system fault indication
- Check engine lamp
- Likely causes
- LikelySignal wire shorted to a voltage feed
- PossibleMissing ground at the gas controller letting its output float high
- PossibleOpen signal wire pulled up inside the reading module
- 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.