P0B42: Hybrid/EV Battery Voltage Sense B Circuit Low

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.

Symptoms

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

Most 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

What to check, in order

Start with the simplest. You can tick off each step.

1. Read the codes with a hybrid-compatible scanner and write down the freeze frame data
2. With the connector unplugged, check whether the signal wire is making contact with ground.
3. Make sure the battery cooling air intake is clean
4. Check the 12 V auxiliary battery, which can also trigger warnings
5. Leave any high-voltage measurements to a specialized repair shop

Good to know

• It can trigger limp mode.
• It affects emissions.

What each character of P0B42 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• B: Subsystem depends on the code range
• 42: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0B42?

If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.

What causes code P0B42?

The most common causes are: 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.

Related codes

• P0B40Hybrid/EV Battery Voltage Sense B Circuit
• P0B41Hybrid/EV Battery Voltage Sense B Circuit Range/Performance
• P0B43Hybrid/EV Battery Voltage Sense B Circuit High
• P0B3DHybrid/EV Battery Voltage Sense A Circuit Low
• P0B16Hybrid/EV Battery Pack Voltage Sense B Circuit Low

Sources

• gsi.ext.gm.com: 19OBDG01 Hybrid Diagnostics
• static.nhtsa.gov: MC 10226030 9999
• law.cornell.edu: 13 CCR 1968.2

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.