Network, generic

U02AB Lost Communication With Vehicle Thermal Management Control Module

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

A vehicle thermal management controller coordinates pumps, valves, fans and the refrigerant circuit that keep cabin, battery and drive electronics at temperature; Marelli markets such an integrated module for electric cars, ready for fast-charge preconditioning and OBD compliance. U02AB means this controller has stopped talking to the rest of the vehicle. Audi lists it for the 2025 A5 and Q5 and the 2026 S5: various cluster messages, control unit 00C5 not reachable, U02AB00 with U042200, cured by a software update. For hybrids, CARB 1968.2 requires the electronic parts of battery and inverter thermal management to be monitored. Expect warnings, limited climate control and, on electrified cars, reduced charging or power.

Likely causes

Thermal management control module software needs an update
Fuse, supply or ground of the module faulty
Bus wiring or connector to the module damaged
Thermal management control module internally failed

Symptoms

  • Several warning messages in the instrument cluster
  • Climate control or battery conditioning limited
  • Reduced charging or drive power on electrified models

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€0–1,500
Time0.3–3 h

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

Parts involved

thermal management modulevehicle bus wiring

Related codes

U05ACU02AEU0623

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