P0B40Hybrid/EV Battery Voltage Sense B Circuit
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- 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.
- What you may notice
- Wrench indicator or MIL, Stop Safely Now message possible
- No start condition
- Battery cannot be charged
- Likely causes
- LikelyOpen cell sense line, splice or bus bar connection inside the pack
- PossibleIntermittent flexible printed circuit cable in the battery controller (Ford Mach-E, e-Transit)
- PossibleInternal traction battery failure requiring replacement (Ford Fusion PHEV)
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €80 – €8,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.