Powertrain, generic · Hybrid propulsion

P0B24 Hybrid/EV Battery A Voltage Unstable

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modePossible

P0B24 reports that the voltage of hybrid/EV battery A is unstable: it swings or jumps more than the battery controller accepts instead of staying steadily too low or too high (P0B25, P0B26). Stellantis lists P0B24-00 with MIL on the Jeep Wrangler 4xe and Grand Cherokee 4xe, together with pack voltage variation, cell balancing and state-of-health codes; the cure is new software for the battery pack control module or, on the 2025 Wrangler, for the hybrid control processor. Some of these Jeeps would not start or reported low 12 V batteries. Ford names P0B24 in the BECM of the 2025 Mustang Mach-E Extended Range, shown with the wrench lamp and fixed by reprogramming. Hardware causes are loose busbar or sense contacts.

Likely causes

Battery controller software (Jeep 4xe BPCM/HCP, Ford BECM updates)

Loose busbar, terminal or sense contact in battery A

Cell with rising internal resistance in battery A

Symptoms

MIL on
Hybrid/EV system or high-voltage battery warning on
Vehicle may not start (Jeep 4xe)
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 abms

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