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U04A9 Invalid Data Received From Hybrid/EV Battery Interface Control Module I

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

U04A9 refers to interface module I, the ninth position in the series. It is the third of the codes Volkswagen lists for the ID.4: in the dealer analysis list of July 2024, U04A9 appears beside U04A1 and U04A5 as a CMCe fault in address 8C, valid for model years 2021 to 2024, with an electrical system message as the complaint. According to Wikipedia the smaller ID.4 battery has nine modules and the larger one twelve, so a ninth position exists in both, though VW does not say how letters map to modules. As with the other two, the helpline must be called before parts are changed. U01A8 marks loss of contact with I, U0342 a software conflict. From J (U04AA) on, the series presupposes larger packs.

Likely causes

Software issue in the battery electronics (VW ID.4 case)
Interface control module I internally faulty
Contact fault on the pack-internal link to module I

Symptoms

  • Electrical system warning message
  • Charging or power restricted

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–3,000
Time1–8 h

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

Parts involved

hv battery interface module i

Related codes

U01A8U0342U04A8U04AAU04A1U04A5

References: static.nhtsa.gov, en.wikipedia.org.