U04A1Invalid Data Received From Hybrid/EV Battery Interface Control Module A
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- U04A1 means the battery management controller keeps receiving messages from interface control module A, one of the slave boards that measure cell voltages and temperatures inside the high-voltage pack, but rejects their content as invalid. Volkswagen names the code: its on-car analysis list of 31 July 2024 for the ID.4 (2021–2024) files U04A1 together with U04A5 and U04A9 under the topic CMCe faults, stored in diagnostic address 8C, with an electrical system warning and no other relevant code there; dealers have to call the VW helpline before repairing. Silence from module A would be U01A0, a software mismatch U033A. Data errors of the battery energy control module itself are a separate code, U0412. Reduced power or no charging is possible until it is fixed.
- What you may notice
- Electrical system or high-voltage battery warning in the cluster
- Reduced drive power
- Charging interrupted or refused
- Likely causes
- LikelySoftware issue in battery management or cell module controllers (VW ID.4 CMCe case, helpline first)
- PossibleInterface control module A internally faulty
- PossibleLoose or corroded connector on the pack-internal data link to module A
- RareWeak 12 V battery disturbing the start-up of the battery electronics
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €100 – €3,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.