Powertrain, generic (extended)

P2C8B Hybrid/EV Battery Interface Control Module B Performance

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P2C8B is the performance fault for the second battery interface control module, B. In GM's Ultium bulletins it never appears alone: PIP6021 applies only if P2C8B is stored together with P2C8A and the module communication codes U3577 to U35AF, and the 2025-26 versions of PIP6081 extend it through U3584 and add U2BAA-U2BB1. That pattern, many modules failing at once, points to a common cause in the BECM software or the module supply rather than to board B itself, so GM tells dealers not to replace hardware but to reprogram, reset and recheck after 10 minutes in Ready. A lone, repeatable P2C8B is different and suggests module B or its harness. CARB asks for battery faults to be pinpointed to the smallest replaceable unit, which is why A and B are separate.

Likely causes

BECM software anomaly affecting several monitoring modules at once
Weak 12 V battery causing a brownout of the monitoring modules
Connector or harness fault at interface module B
Interface module B itself defective

Symptoms

  • MIL or high-voltage service message
  • Discharged 12 V battery

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–5,000
Time1.5–8 h

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

Parts involved

hybrid battery interface cm bbms

Related codes

P2C8AU01A1U033BU04A2

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