P0B29Hybrid/EV Battery B Voltage Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P0B29 sets when the voltage of hybrid/EV battery B stays below the range the controller expects for the present state of charge and load. It is the low counterpart to P0B2A; fluctuating readings belong to P0B28 and the general fault to P0B27. No manufacturer publishes a definition of P0B29; Jeep 4xe bulletins confirm the use of a separately monitored battery B only through P0B28. GM handles the analogous whole-pack undervoltage with P0ABC (pack voltage below 24 V). CARB requires battery voltage sensors and cells to be monitored and the fault to be narrowed to the smallest replaceable unit. Weak or deeply discharged cells in that unit are the usual reason, so the controller cuts discharge power and may block driving in EV mode.
- What you may notice
- Hybrid/EV system or high-voltage battery warning on
- MIL on
- Battery power limited, less electric drive or assist
- Electric-only driving unavailable
- Likely causes
- LikelyAged cells with lost capacity in battery B
- PossibleDeep discharge or self-discharge after standstill
- RareVoltage measurement fault in the controller or sense leads
- 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 – €4,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.