U04A2Invalid Data Received From Hybrid/EV Battery Interface Control Module B
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- U04A2 covers the second interface board of the high-voltage pack, module B: its frames reach the battery controller but carry implausible content. No manufacturer documents this exact code publicly. The closest published logic is GM's 2016 hybrid table 16OBDG02, where the battery systems module talks to eight interface boards, A to H, over a serial UART daisy chain. If no data at all arrive from B for 5 s at more than 10.2 V, GM logs the lost-link sibling U01A1 as Type A, after first trying a loop-back test that bypasses the chain. U04A2 is the opposite case: the link exists, the content fails. CARB lists battery voltage sensors among the hybrid storage inputs that OBD has to check. Software issues fall under U033B.
- What you may notice
- Hybrid or EV system warning, MIL on plug-in hybrids
- Electric range or power reduced
- Likely causes
- PossiblePoor contact in the chain connection between interface boards A, B and C
- PossibleInterface control module B internally faulty
- PossibleOutdated calibration in the battery controller
- 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 – €2,800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.