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U04AB Invalid Data Received From Hybrid/EV Battery Interface Control Module K

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

U04AB means interface module K, the eleventh, delivers data the battery controller judges invalid. What those boards report, cell voltages and temperatures, are exactly the inputs that CARB rule 1968.2, paragraph (e)(15.2.3)(A)(iv), names for monitoring in a hybrid energy storage system; this is why plug-in hybrids light the MIL for such faults, while battery-electric cars, which fall outside these rules, show a battery or system warning instead. With part of the pack unreadable, the controller has to assume the worst for those cells: tighter charge and discharge limits or a blocked charge. No manufacturer documents U04AB publicly, and an eleventh board only exists in larger packs. U01AA covers loss of contact, U0344 a software mismatch.

Likely causes

Faulty temperature or voltage input on board K
Contact fault on the internal data link to module K
Interface control module K internally faulty

Symptoms

  • MIL (plug-in hybrid) or battery warning (EV)
  • Charging blocked or slowed
  • Reduced acceleration

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€150–3,500
Time2–10 h

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

Parts involved

hv battery interface module k

Related codes

U01AAU0344U04AAU04AC

References: law.cornell.edu, gsi.ext.gm.com.