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U01A5 Lost Communication With Hybrid/EV Battery Interface Control Module F

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

U01A5 says the battery controller no longer receives data from interface module F. Once such a board drops out, the cells it covers are unsupervised: no voltage readings, no temperatures and no balancing for that section. GM therefore puts all of these codes into a fault bundle called BICM Loss of Comm in its 2018 hybrid table, which blocks battery diagnostics that would otherwise misfire on missing values. On the road the controller shields the pack, so reduced power, refused charging or opened contactors are to be expected. Audi bulletin 2078135 for the 2016 A3 Sportback e-tron describes a drive system that cannot be activated and a red warning lamp, with U01A500 among the A-H codes plus P0AA500 and P0A7D00. GM monitors F as Type A from 2016 to 2019.

Likely causes

Chain connection between module E and module F interrupted
Battery interface control module F defective
Board F loses supply because its cell group or sense tap is open

Symptoms

  • Drive system cannot be activated, red warning lamp
  • Charging refused or stopped early
  • Other battery diagnostics suspended while the code is active

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 fcommunication bus

Related codes

U01A4U01A6U04A6U033FP0AA5

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