Network, generic

U04A2 Invalid Data Received From Hybrid/EV Battery Interface Control Module B

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modePossible

U04A2 covers the second interface board of the high-voltage pack, module B: its frames reach the battery controller but carry implausible content. No manufacturer documents this exact code publicly. The closest published logic is GM's 2016 hybrid table 16OBDG02, where the battery systems module talks to eight interface boards, A to H, over a serial UART daisy chain. If no data at all arrive from B for 5 s at more than 10.2 V, GM logs the lost-link sibling U01A1 as Type A, after first trying a loop-back test that bypasses the chain. U04A2 is the opposite case: the link exists, the content fails. CARB lists battery voltage sensors among the hybrid storage inputs that OBD has to check. Software issues fall under U033B.

Likely causes

Poor contact in the chain connection between interface boards A, B and C

Interface control module B internally faulty

Outdated calibration in the battery controller

Symptoms

Hybrid or EV system warning, MIL on plug-in hybrids
Electric range or power reduced

Repair estimate

DifficultyShop_onlyWorkshop job

Parts and labour€100–2,800

Time1–8 h

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

Parts involved

hv battery interface module b

Related codes

U01A1 U033B U04A1 U04A3 U0412

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