Powertrain, generic · Hybrid propulsion

P0B28 Hybrid/EV Battery B Voltage Unstable

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Battery pack control module software (Jeep 4xe update)
Loose busbar, terminal or sense contact in battery B
Cell with rising internal resistance in battery B

Symptoms

  • 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

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€80–3,000
Time0.5–8 h

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

Parts involved

hv battery bbms

Related codes

P0B27P0B29P0B2AP0B24P0BBEP0DAB

References: static.nhtsa.gov, law.cornell.edu.