Powertrain, generic · Hybrid propulsion

P0B21 Hybrid/EV Battery Pack Voltage Sense D Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Sense lead of channel D shorted to a higher potential
Evaluation error in battery controller software
Measurement input of the battery controller defective

Symptoms

  • 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

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–2,500
Time1–6 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

hv battery pack voltage sense dwiring harnessbms

Related codes

P0B1EP0B1FP0B20P0B22P0B1CP0ABD

References: gsi.ext.gm.com, law.cornell.edu.