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U01AA Lost Communication With Hybrid/EV Battery Interface Control Module K

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

U01AA covers battery interface control module K, the eleventh board, so only large packs can set it at all. Not every design uses wires for this link: GM's Ultium platform monitors its cells by radio, a system developed with Analog Devices, which according to Wikipedia needs about 90 % less wiring. With such a layout a lost module is a radio node the controller no longer hears; checks then move from harness and plugs to the node's supply, interference and the correct registration of any replacement board. No manufacturer publicly ties U01AA to a vehicle; GM includes it only in the fault bundle of its 2018 hybrid table, which lists module codes up to M, without a monitor entry or MIL type of its own.

Likely causes

Wired link to K interrupted or, in wireless systems, radio link lost
Replacement board K not registered with the battery controller
Battery interface control module K defective

Symptoms

  • Battery warning, reduced range and power
  • DC fast charging limited or refused

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–3,500
Time1–10 h

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

Parts involved

hv battery interface module kcommunication bus

Related codes

U01A9U01ABU04ABU0344

References: en.wikipedia.org, gsi.ext.gm.com, law.cornell.edu.