P0B4AHybrid/EV Battery Voltage Sense D 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
- 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.
- What you may notice
- No start or vehicle will not go into ready mode
- Charging not possible
- Several sense channel codes stored together
- Likely causes
- 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)
- 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.