P25C1
Alternative Fuel Disable Signal Circuit
The feedback signal that confirms the alt-fuel disable command was carried out is missing or out of range. The fuel system cannot verify that the gas circuit is shut.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- Open feedback wire between relay and control moduleCommon
- Feedback contact in the disable relay corroded or stuckPossible
Parts involved
- Alt Fuel Control Module
- Feedback Sensor
- Wiring Harness
P25C1 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.