P25AF code meaning
Coolant Temperature Control Module Requested MIL Illumination
Powertrain system Generic code P25xx codes Check engine light
What P25AF means
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.
P25AF at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyHard
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P25AF
- Check engine lamp on
- Possible temperature warnings or reduced heating
Common causes of P25AF
- Most likelyEmission-relevant fault stored in the coolant temperature control module
- PossibleFaulty coolant valve, pump or sensor handled by that module
- Less likelyThermal module software needing an update
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Coolant temp control module
What each part of P25AF 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. |
| AF | The exact fault in that area. |
What to do next
- Note P25AF 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 P25AF
What does P25AF mean?
P25AF means "Coolant Temperature Control Module Requested MIL Illumination". P25AF is a messenger code. It is a generic code, so it means the same on every make.
Is it safe to drive with P25AF?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P25AF fail an emissions test?
Yes, it can. P25AF 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 P25AF to fix?
Difficulty: hard. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will P25AF clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.