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U04AD Invalid Data Received From Hybrid/EV Battery Interface Control Module M

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

With U04AD the series reaches module M, the thirteenth interface board, which only exists in packs larger than the common twelve-module layout. One example of such a size is GM's Hummer EV: Wikipedia describes its Ultium battery as 24 modules in two layers that can be switched from parallel to series for 800 V fast charging. How GM names the monitoring electronics in that pack is not published, and no maker documents U04AD. The code says the battery controller receives M's frames but rejects their content; corrupted counters, checksums or impossible cell values are typical reasons in this code family. Loss of contact would be U01AC, a software mismatch U0346. Reduced power or charging is the likely consequence.

Likely causes

Corrupted frames on the internal link (counter or checksum errors)
Interface control module M faulty
Measurement input on board M reporting impossible values

Symptoms

  • Battery system warning
  • Fast charging slower or refused

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€200–4,000
Time2–10 h

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

Parts involved

hv battery interface module m

Related codes

U01ACU0346U04ACU04AE

References: en.wikipedia.org, gsi.ext.gm.com.