Network, generic

U01A8 Lost Communication With Hybrid/EV Battery Interface Control Module I

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

U01A8 is the code for battery interface control module I and is only needed on packs with more than eight monitoring boards. GM's 2018 hybrid table contains it solely inside the fault bundle BICM Loss of Comm (U01A0-U01AC), adding that GM shares software across programs and only codes valid for the vehicle at hand apply; there is no monitor entry of its own, so neither threshold nor MIL type is published for I. Packs of that size exist: according to Wikipedia, the Ultium battery of the Hummer EV holds 24 modules, but which systems really use U01A8 remains undocumented. When it appears, the battery controller has lost the ninth board of its chain while the eight before it still answer. CARB requires separate codes per replaceable unit.

Likely causes

Chain connection between module H and module I interrupted
Battery interface control module I defective
Battery controller configured for more boards than fitted

Symptoms

  • Battery or hybrid warning, power limited
  • Charging blocked

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–3,000
Time1–8 h

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

Parts involved

hv battery interface module icommunication bus

Related codes

U01A7U01A9U04A9U0342

References: gsi.ext.gm.com, en.wikipedia.org, law.cornell.edu.