P0DB9Hybrid/EV Battery Cell Balancing Circuit D Stuck On
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- A stuck-on circuit D (P0DB9) drains group D continuously. The usual check is simple: does the switch state reported back equal the state the controller asked for? GM applies this on the eAssist battery for a related code, sampling every 200 ms and logging a Type B fault after 7 mismatches in 10. Here the reported state stays on while the command says off. Besides the voltage loss, the bleed resistor keeps warming its part of the module, which can upset temperature readings nearby. On Ford hybrids the code is real: the 2019 OBD summary checks circuit D for 0.1 s at each start, before the high voltage contactors close, against a 75 mV deviation of any of its six cells from the average. The broken-circuit case is P0DB8, the inactive case P0DBA.
- What you may notice
- MIL with battery warning
- Group D cells and their local temperature deviating
- Loss of charge while parked
- Likely causes
- LikelyBalancing transistor of circuit D shorted
- PossibleStatus feedback of the module wrong, switch actually fine
- RareDrive output of the monitoring chip stuck on
- 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: €300 – €4,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.