Powertrain, generic (extended)

P2D8B Fan 2 Control Module Performance

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modeNo

With P2D8B the module that drives fan 2 fails a plausibility or self-test: it has supply and receives a request, yet the status or speed it reports does not fit. Audi's TSB 2081184/1 for the 2025 Q5 family lists P2D8B next to P2D88 and the local LIN bus error U366500, all stored in the thermal management control unit (address 00C5). In those cars earth point 642 of the electrically controlled fan at the front right had been fitted incorrectly; production changed on 28 May 2025, and in service the ground is checked and repaired, with photos for the warranty claim. On other vehicles a worn motor, foreign objects in the blades or water in the connector are more likely. Typical complaints are a lit engine warning lamp and an air conditioning that no longer cools. Fan 1 has P2D88.

Likely causes

Damaged or incorrectly fitted ground point of fan 2

Foreign objects or worn bearings slowing fan 2

Internal electronics fault of the fan 2 module

Water ingress or corrosion at connector or LIN line

Symptoms

Engine warning lamp on
Air conditioning without cooling
Fault stored intermittently or permanently

Repair estimate

DifficultyMediumWorkshop job

Parts and labour€80–800

Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

fan control module 2wiring harnessecm

References: static.nhtsa.gov, law.cornell.edu.