Network, generic

U05AC Invalid Data Received From Vehicle Thermal Management Control Module

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

Electrified cars increasingly run cabin, battery and drive-unit cooling from one thermal management controller that commands pumps, valves, fans and the refrigerant circuit; suppliers such as Hirain and Marelli sell such units, Marelli explicitly with OBD compliance. For hybrids, CARB requires the electronic parts used for battery and inverter cooling or heating to be monitored and, where feasible, the cooling performance itself. U05AC is stored when that controller's status or temperature messages reach another module with invalid content. Audi reports the partner U02AB, the thermal management unit 00C5 not reachable, on the 2025/26 A5, Q5 and S5 with a software fix (index entry only). No maker documents U05AC itself. Charging and drive power may be limited to protect the battery.

Likely causes

Thermal management controller software out of date
Faulty temperature or pressure sensor feeding the controller
Controller internally faulty

Symptoms

  • Various warning messages in the cluster
  • Reduced charging or drive power
  • Climate control not working properly

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–1,500
Time0.3–3 h

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

Parts involved

thermal management module

Related codes

U02AB

References: en.hirain.com, marelli.com, law.cornell.edu.