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U01A1 Lost Communication With Hybrid/EV Battery Interface Control Module B

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

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.

Likely causes

Chain connection between module A and module B interrupted or corroded
Battery interface control module B (GM K112B) defective
Common low-voltage feed of the powerpack interrupted (then usually A as well)

Symptoms

  • MIL only after two consecutive failing trips (GM Type B)
  • Start-stop and electric assist unavailable
  • Hybrid system warning message

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–2,500
Time1–6 h

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

Parts involved

hv battery interface module bcommunication bus

Related codes

U01A0U01A2U04A2U033BU0111

References: static.nhtsa.gov, gsi.ext.gm.com, gsi.ext.gm.com.