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U0349 Software Incompatibility With Hybrid/EV Battery Interface Control Module P

Check engine lightUsually off
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P is the sixteenth and final letter; the following number, U034A, already names an engine disconnect clutch, so a pack with more than sixteen boards would need maker codes. No vehicle is publicly linked to U0349. A real case of out-of-date battery firmware comes from Rivian: in 2022 R1T trucks built from October 2021 to June 2022, an old BMS firmware version could block over-the-air updates, so campaign RCA-30-23-001 had technicians remove an underbody panel, read a serial label and escalate for a manual update. A version gap can thus stop the update path itself, which is why a mismatch needs the maker's flashing tool. CARB's hybrid rules cover cell sensing; battery-only vehicles fall outside OBD II. U01AF and U04B0 are P's partners.

Likely causes

Battery firmware so old that over-the-air updates cannot be applied
Sixteenth board replaced without matching software
Code confused with U034A, which belongs to another component

Symptoms

  • Software updates fail or are not offered
  • Battery warning after battery service
  • Charging or power limited in severe cases

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€0–600
Time0.3–3 h

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

Parts involved

hv battery interface module p

Related codes

U01AFU04B0U0348

References: static.nhtsa.gov, law.cornell.edu.