U01A1Lost Communication With 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
- Needs a drive cycle to confirm a fix
- How the car detects it
- U01A1 refers to battery interface control module B. In GM's eAssist mild hybrids it is the second and final board: bulletin PIT5513D lists two high-voltage battery interface control modules, K112A and K112B, for Silverado and Sierra trucks of 2016 to 2018 and the 2018 LaCrosse, and the GM tables 16OBDG07B and 19OBDG03B accordingly contain only U01A0 and U01A1. Their rating is milder than in the plug-in hybrids: Type B, so the MIL waits for a second failing trip; the 2016 table asks for more than 9.1 V and 4.5 s. If B is logged alone, the fault lies at B or at the link from A to B; both letters together point rather to a shared feed or the master side. GM placed these powerpacks and both boards under parts restriction via its technical assistance center.
- What you may notice
- MIL only after two consecutive failing trips (GM Type B)
- Start-stop and electric assist unavailable
- Hybrid system warning message
- Likely causes
- LikelyChain connection between module A and module B interrupted or corroded
- PossibleBattery interface control module B (GM K112B) defective
- RareCommon low-voltage feed of the powerpack interrupted (then usually A as well)
- 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 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.