What are the common causes of P0B40?

Corroded or damaged wiring in the voltage sense B circuit. A failed voltage sensor on circuit B. A weak or failing battery feeding sense B. The battery installed incorrectly so sense B misreads. Control module software fault on circuit B.

Inspect sense B wiring and connectors for corrosion. Read sense B voltage live and compare to spec. Test the voltage sensor on circuit B. Verify battery installation. Update the control module software. Clear the code and retest.

P0B40

Hybrid/EV Battery Voltage Sense B Circuit

System: Powertrain control (P code)
Lamp: Check Engine Light
Category: Powertrain - Hybrid Propulsion

What it means

P0B40 means Hybrid/EV Battery Voltage Sense B Circuit.

Check these first

Corroded or damaged wiring in the voltage sense B circuit
A failed voltage sensor on circuit B
A weak or failing battery feeding sense B
The battery installed incorrectly so sense B misreads
Control module software fault on circuit B

What to do next

Inspect sense B wiring and connectors for corrosion
Read sense B voltage live and compare to spec
Test the voltage sensor on circuit B
Verify battery installation
Update the control module software
Clear the code and retest

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Updated

Generic SAE J2012 definition. Last updated 2026-10-10.