Powertrain, generic · Hybrid propulsion

P0DD9 Hybrid/EV Battery Cell Balancing Circuit L Stuck On

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modePossible

P0DD9: the balancing path of group L will not switch off. The 2018 edition of Ford's hybrid OBD summary contains the code; the BECM catches it at power-up with the contactors still open, in a 100 ms check that compares each of the six cells of circuit L with the average and fails above 75 mV, again over two power cycles. GM shows a different route in its 2013 eAssist table: code P1B33 compares the reported balancing switch status with the commanded one and fails after 7 of 10 samples, as a two-trip fault. A switch that reads on while it should be off is exactly what P0DD9 describes. While parked the group drains, and the warm resistor stresses the module. Inactive opposite: P0DDA.

Likely causes

Balancing switch of group L shorted

Balancing command for L not cleared by the monitoring electronics

Switch status feedback of channel L reporting on although the switch is open

Symptoms

Check engine light after switching on
Group L lower than the others after standing
Less electric range

Repair estimate

DifficultyShop_onlyWorkshop job

Parts and labour€300–4,500

Time1.5–8 h

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

Parts involved

hv battery cell balancing circuit lbms

References: law.cornell.edu, fordservicecontent.com, gsi.ext.gm.com.