P0B21Hybrid/EV Battery Pack Voltage Sense D Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P0B21 means pack voltage measurement D reports more than its plausible maximum. As with the other high codes, the measurement path is the main suspect, for example a sense lead shorted to a higher potential, a faulty input stage or an evaluation error in software, not an actual overcharged pack. No manufacturer documents P0B21 publicly. For channel A GM's BECM sets P0ABD above 479 V for 1.6 s in 2 s, Type A, and Mercedes-Benz records the channel B variant P0B17 on the eSprinter. CARB requires out-of-range monitoring of battery voltage sensors. The low counterpart is P0B20. High-voltage operation is usually blocked or limited until the fault is cleared.
- What you may notice
- MIL and hybrid/EV system warning on
- Vehicle may not reach Ready or may shut down the high-voltage system
- Battery power limited, reduced electric drive or assist
- Likely causes
- LikelySense lead of channel D shorted to a higher potential
- PossibleEvaluation error in battery controller software
- PossibleMeasurement input of the battery controller 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 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.