P2C8BHybrid/EV Battery Interface Control Module B Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- 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.
- What you may notice
- MIL or high-voltage service message
- Discharged 12 V battery
- Likely causes
- LikelyBECM software anomaly affecting several monitoring modules at once
- PossibleWeak 12 V battery causing a brownout of the monitoring modules
- RareConnector or harness fault at interface module B
- RareInterface module B itself defective
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €100 – €5,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.