P0B4A code meaning
Hybrid/EV Battery Voltage Sense D Circuit
Powertrain system Generic code P0Bxx codes Check engine light
What P0B4A means
P0B4A is the open-circuit code of cell sense channel D, the fourth measuring channel of the battery monitoring electronics. GM checks it in the battery energy control module with the same open sense line logic as the other channels: a gap of 1.3 V or more between adjacent cells, under 36 mV on a cell being balanced, or splice voltages above 0.1 V or 0.5 V at a bus bar, for 0.6 s, Type A. For diagnosis, the pattern matters: if P0B4A stands alone, inspect the channel D tap and its connector; if Ford's whole open-line group from P0B3B upwards is set, as on the 2019-2020 Fusion PHEV or the 2023 Mach-E and E-Transit, a common cause such as the BECM flex cable or the battery itself is more likely.
P0B4A at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor0.5 to 8 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0B4A
- No start or vehicle will not go into ready mode
- Charging not possible
- Several sense channel codes stored together
Common causes of P0B4A
- Most likelyOpen channel D sense tap or connector (code set alone)
- PossibleFaulty BECM flexible printed circuit affecting several channels (Ford Mach-E, E-Transit)
- PossibleInternal traction battery fault (Ford Fusion PHEV)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Hv battery voltage sense dWiring harnessBms
What each part of P0B4A means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| B | Area: hybrid propulsion. |
| 4A | The exact fault in that area. |
What to do next
- Note P0B4A and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0B4A
What does P0B4A mean?
P0B4A means "Hybrid/EV Battery Voltage Sense D Circuit". P0B4A is the open-circuit code of cell sense channel D, the fourth measuring channel of the battery monitoring electronics. It is a generic code, so it means the same on every make.
Is it safe to drive with P0B4A?
Drive gently and only to a workshop. With P0B4A the car can go into limp mode (reduced power) to protect itself.
Will P0B4A fail an emissions test?
Yes, it can. P0B4A is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0B4A to fix?
Difficulty: workshop only. A typical repair takes 0.5 to 8 hours of work. This is a job for a workshop.
Will P0B4A clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.