P0B28Hybrid/EV Battery B Voltage Unstable
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P0B28 flags an unstable voltage of hybrid/EV battery B: the reading fluctuates beyond what the battery controller tolerates. Stellantis documents it with P0B28-00 on the Jeep Wrangler 4xe: the MIL is on, and the bulletin warns that after 49 days with this MIL lit the vehicle is no longer allowed to start. The remedy is new software for the battery pack control module, issued first as a rapid service update and later as a regular bulletin; recall 95B must be completed first. The same bulletin lists P0B24 for battery A and codes for voltage variation and cell balancing. Steady low or high voltages of battery B are P0B29 and P0B2A. Besides software, loose busbar or sense contacts can produce the same pattern.
- What you may notice
- MIL on
- Start inhibited after a long period with the MIL lit (Jeep 4xe: 49 days)
- Hybrid/EV system or high-voltage battery warning on
- Warning comes and goes, fault often stored as intermittent
- Likely causes
- LikelyBattery pack control module software (Jeep 4xe update)
- PossibleLoose busbar, terminal or sense contact in battery B
- RareCell with rising internal resistance in battery B
- 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: €80 – €3,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.