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U0346 Software Incompatibility With Hybrid/EV Battery Interface Control Module M

Check engine lightUsually off
EmissionsRelevant
Drive cycleNot required
Limp modePossible

With M the row passes the common twelve-board size. GM's 2018 hybrid table 18OBDG02 includes lost-contact codes for interface modules up to M (U01AC) in its bundle BICM Loss of Comm and adds that GM shares software across programs, so a code counts only where the program in question uses it. A matching bundle for software codes such as U0346 is not listed. The one GM pack plainly beyond twelve modules is the Hummer EV, whose Ultium battery Wikipedia describes as two layers of twelve modules each, wired in parallel at 400 V. How GM addresses the monitoring units in that pack is not published, so no vehicle is known to set U0346. U04AD is M's invalid-data code.

Likely causes

Thirteenth board on a software level the controller rejects
Controller software variant for another pack configuration
Board installed in the wrong layer or position of a multi-layer pack

Symptoms

  • Battery or propulsion warning
  • Power or charging limited
  • Code seen only on very large packs

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€80–1,200
Time0.5–4 h

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

Parts involved

hv battery interface module m

Related codes

U01ACU04ADU0345U0347

References: gsi.ext.gm.com, en.wikipedia.org.