Powertrain, generic · Hybrid propulsion

P0B42 Hybrid/EV Battery Voltage Sense B Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P0B42 sets when cell voltage channel B reads implausibly low, below what any usable cell would show. GM's battery energy control module sets it at 0.2 V or less for 1.4 s within a 2 s window, Type A, one trip, and only when no open sense line, slave communication or balancing fault is present. FCA uses P0B42 as Voltage Sense 2 Circuit Low on the 2022 Grand Wagoneer and Wagoneer with the 5.7 L eTorque mild hybrid; its bulletin calls the MIL false, mentions inoperative start-stop and a car that seems to run on fuel only, and prescribes a battery pack control module update. Cells that are actually weak set separate cell voltage codes. High and range faults are P0B43 and P0B41.

Likely causes

Battery pack control module software causing a false MIL (FCA eTorque)
Sense line shorted to the adjacent line or to the cell negative
Measurement input of the cell monitoring chip failed

Symptoms

  • MIL on
  • Start-stop inoperative
  • Vehicle behaves as if running on the engine only

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€50–5,000
Time0.2–6 h

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

Parts involved

hv battery voltage sense bwiring harnessbms

Related codes

P0B40P0B41P0B43P0B3DP0B16

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