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U04AA Invalid Data Received From Hybrid/EV Battery Interface Control Module J

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

U04AA flags invalid data from interface module J, the tenth slot. From here on the series only matters for packs with ten or more monitored sections; a nine-module ID.4 battery or an eight-board GM pack like the one in table 16OBDG02 has no J at all. GM's Ultium family, by contrast, assembles packs from anywhere between six and 24 modules of one design, per Wikipedia, and the larger ones clearly exceed ten. No manufacturer publishes U04AA or a threshold for it, and none of the indexed service bulletins mentions it. Likely triggers are the same as for the lower letters: a disturbed isolated link, a damaged connector or a faulty board. U01A9 means J is silent, U0343 incompatible software.

Likely causes

Disturbed isolated data link inside the pack
Damaged connector at module J
Interface control module J faulty

Symptoms

  • Battery or EV system warning
  • Power or charging rate reduced

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 j

Related codes

U01A9U0343U04A9U04AB

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