P0B31Hybrid/EV Battery D 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
- P0B31 is stored when the voltage of hybrid/EV battery D stays below the expected range. High voltage of the same unit sets P0B32, fluctuation P0B30 and an unspecified deviation P0B2F. No manufacturer publishes a definition of P0B31; Bentley's P0B25 for battery A is the closest documented example, with the energy store replaced once the cell spread reaches 0.5 V. GM uses P0ABC for an undervoltage of the whole pack (below 24 V). CARB asks for monitoring of cells and voltage sensors in hybrid storage and for fault codes that single out the replaceable unit. Typical is a module in unit D that has aged faster or self-discharged during standstill. Discharge power and electric range drop, and the controller may stop electric driving.
- What you may notice
- Hybrid/EV system or high-voltage battery warning on
- MIL on
- Battery power limited, less electric drive or assist
- Reduced electric range
- Likely causes
- LikelyAged cells with lost capacity in battery D
- 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.