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U04A3 Invalid Data Received From Hybrid/EV Battery Interface Control Module C

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modePossible

U04A3 concerns interface module C. Such boards do more than measure: they also switch the balancing resistors that bleed charge from individual cells. CARB 1968.2 section (e)(15.2.3) requires hybrid OBD to confirm that cell balancing still holds the cell voltages where intended, and GM checks this per board in 16OBDG02 by closing the odd and even balancing gates in turn and comparing readings, for module C under P1E9E. When the battery controller cannot trust what module C sends, it can neither balance nor judge those cells, so it usually limits power. No manufacturer publishes U04A3 itself. U01A2 marks a silent module C, U033C incompatible software; module D's data fault is filed as U02A0, because U04A4 belongs to the particulate sensor.

Likely causes

Interface control module C faulty (measurement or balancing stage)

Damaged cell sense lead or connector at module C

Interference or contact fault on the pack-internal data link

Symptoms

Hybrid or EV warning, MIL on plug-in hybrids
Power limited, state of charge shown inaccurately

Repair estimate

DifficultyShop_onlyWorkshop job

Parts and labour€150–3,000

Time1.5–8 h

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

Parts involved

hv battery interface module c

Related codes

U01A2 U033C U04A2 U02A0 U0412

References: law.cornell.edu, gsi.ext.gm.com.