P25BF
Alternative Fuel Disable Control Circuit High
Voltage on the alternative-fuel disable control line is above the expected window. Often a short to battery upstream of the relay or a stuck-on driver in the control module.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- Disable control wire shorted to a B+ supplyCommon
- Output driver stuck on inside the control modulePossible
- Connector pins corroded - high contact resistanceLess likely
Parts involved
- Alt Fuel Control Module
- Wiring Harness
P25BF 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.