P25C2 code meaning
Alternative Fuel Disable Signal Circuit High
Powertrain system Generic code P25xx codes Check engine light
What P25C2 means
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.
P25C2 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P25C2
- Vehicle stays on gasoline
- Gas system fault indication
- Check engine lamp
Common causes of P25C2
- Most 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
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Alt fuel control moduleWiring harness
What each part of P25C2 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 5 | Area: vehicle speed, idle control and auxiliary inputs. |
| C2 | The exact fault in that area. |
What to do next
- Note P25C2 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P25C2
What does P25C2 mean?
P25C2 means "Alternative Fuel Disable Signal Circuit High". P25C2 means the alternative fuel disable signal arriving at the engine controller sits above its valid range. It is a generic code, so it means the same on every make.
Is it safe to drive with P25C2?
Drive gently and only to a workshop. With P25C2 the car can go into limp mode (reduced power) to protect itself.
Will P25C2 fail an emissions test?
Yes, it can. P25C2 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P25C2 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will P25C2 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.