U01ABLost Communication With Hybrid/EV Battery Interface Control Module L
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- U01AB points at battery interface control module L, the twelfth position. The link to such a board has to bridge a large voltage offset, because the lowest and highest boards of a stack sit hundreds of volts apart. NXP's MC33771C, as one example, talks over a two-wire twisted pair coupled through transformers or capacitors at up to 2 Mbit/s, and Wikipedia's battery management article mentions optical isolation and radio as the alternatives. A broken coupling element or a damaged twisted pair at L can therefore cut the board off while it still measures correctly. No vehicle maker documents U01AB with a threshold of its own; GM lists it only in the 2018 fault bundle BICM Loss of Comm, so how the MIL behaves depends on the individual system.
- What you may notice
- Battery or hybrid warning
- Power limited, charging may be blocked
- Likely causes
- LikelyTwisted-pair chain line to module L chafed, pinched or unplugged
- PossibleIsolating transformer or capacitor on the link to L failed
- RareBattery interface control module L defective
- 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: €150 – €3,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.