P25AFCoolant Temperature Control Module Requested MIL Illumination
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- P25AF is a messenger code. A separate coolant temperature control module, used on some vehicles with electrically managed cooling for engine, battery or power electronics, has stored an emission-relevant fault of its own and asks the engine module to turn on the check engine lamp. CARB's OBD II rule expects lamp requests from other powertrain units to be passed on reliably. No manufacturer publicly documents P25AF with this meaning; the nearest documented relatives are GM's brake module requests P25A2 and P25C9, held in the engine module as Type A without a separate lamp command. Volkswagen's 2014 Touareg Hybrid data book still used P25AF for an engine hood switch message fault on CAN. The actual cause has to be read out of the thermal module.
- What you may notice
- Check engine lamp on
- Possible temperature warnings or reduced heating
- Likely causes
- LikelyEmission-relevant fault stored in the coolant temperature control module
- PossibleFaulty coolant valve, pump or sensor handled by that module
- RareThermal module software needing an update
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €50 – €1,200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.