Powertrain, generic · Hybrid propulsion

P0B40 Hybrid/EV Battery Voltage Sense B Circuit

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modePossible

P0B40 is the circuit code of cell voltage sense channel B, the second cell or cell group the battery monitoring electronics measures; pack-level voltage uses P0ABA and P0B14 ff instead. GM applies the same open sense line test as on channel A: a 1.3 V jump between neighbouring cells, under 36 mV with balancing on, or splice voltage above 0.1 V (bus bar 0.5 V) for 0.6 s, Type A, one trip. Ford lists P0B40 among the open-line codes on the 2019-2020 Fusion PHEV, where the fix is a new traction battery, and on the 2023 Mustang Mach-E and e-Transit, where an intermittent flexible printed circuit cable in the battery controller is to blame. Expect no start or no charging.

Likely causes

Open cell sense line, splice or bus bar connection inside the pack

Intermittent flexible printed circuit cable in the battery controller (Ford Mach-E, e-Transit)

Internal traction battery failure requiring replacement (Ford Fusion PHEV)

Symptoms

Wrench indicator or MIL, Stop Safely Now message possible
No start condition
Battery cannot be charged

Repair estimate

DifficultyShop_onlyWorkshop job

Parts and labour€80–8,000

Time0.5–8 h

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

Parts involved

hv battery voltage sense bwiring harnessbms

Related codes

P0B41 P0B42 P0B43 P0B44 P0B3B P0B45

References: gsi.ext.gm.com, static.nhtsa.gov, static.nhtsa.gov, law.cornell.edu.