P25C3Alternative Fuel Disable Signal Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P25C3 is logged when the alternative fuel disable signal reaching the engine controller is too low to be valid. A short to ground on the way from the gas system, a gas controller that has lost its supply, or a damaged output stage in that controller can each pull the line down. On a gas installation that announces a block by grounding the line, this would also be indistinguishable from a genuine stop request, so the engine controller has to treat gas operation as unavailable. GM's 2016 bi-fuel trucks illustrate the fallback: they start on gasoline and only change over once the conditions for gas operation have been met, and a failed changeover is shown with the fuel indicator. No manufacturer documents P25C3 publicly. The general signal fault is P25C1, the opposite case P25C2.
- What you may notice
- No change-over to gas operation
- Fuel mode indicator flashes or shows a fault
- Check engine lamp
- Likely causes
- LikelySignal wire shorted to ground
- PossibleGas controller without supply voltage
- RareDamaged output stage in the gas controller
- 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.