P0DB2: Hybrid/EV Battery Cell Balancing Circuit B Stuck Off

What does P0DB2 mean?

Stuck off on circuit B (P0DB2) is the passive failure: the command arrives, but the bleed resistor of that group carries no current, so its high cells are never trimmed. LG Chem's patent EP2730933A1 tests for this by switching the balancing circuit on and off and watching how the voltage across a diagnosis resistor reacts; no change means a dead circuit. The result builds up over many charges: cells of group B reach the upper limit first and end charging early, while the rest stay below. CARB 13 CCR 1968.2 counts this as a balancing malfunction. Ford lists P0DB2 in its 2016 hybrid OBD summary: the BECM bleeds only the highest cells down to the others and judges each six-cell circuit once per power-up against a 75 mV limit. Compare P0DB1 for the opposite fault.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• MIL and battery warning
• Charging stops before the expected state of charge
• High cell voltages in group B in live data

Common causes

• High Bleed resistor of group B burnt open
• Medium Balancing transistor of circuit B no longer switching
• Low Open terminal or cell tap connection in group B

Likelihood is a general estimate across vehicles; your make and model may differ.