Powertrain, generic · Hybrid propulsion

P0DB5 Hybrid/EV Battery Cell Balancing Circuit C Stuck On

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

Circuit C stuck on (P0DB5) means the cells of group C bleed energy permanently, also with the car switched off. Designers guard against exactly this: the LaunchPoint patent US8598840B2 lets every balance enable expire on a timer unless the central controller renews it, so a lost command cannot leave a switch on. When the hardware itself fails closed, that guard does not help and the controller can only spot the falling voltage or the mismatch between command and switch state. Over a few days the group C cells can drop far enough to trigger low cell voltage codes. Ford's 2017 hybrid OBD summary tests circuit C in a 100 ms window each time the car wakes, contactors still open, and sets P0DB5 if one of its six cells is more than 75 mV off the average.

Likely causes

Balancing transistor in circuit C failed closed
Enable or watchdog logic of the module not releasing the switch
Leakage path on the module board

Symptoms

  • MIL with battery warning, often after standing
  • Low cell voltage codes in group C as a follow-up
  • Electric range dropping

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€300–4,000
Time2–8 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

hv battery cell balancing circuit cbms

Related codes

P0DABP0DB4P0DB6P0DB7P0DE6

References: law.cornell.edu, patents.google.com, fordservicecontent.com.