P0DD9: Hybrid/EV Battery Cell Balancing Circuit L Stuck On

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.

High severity. Can I keep driving?If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.

Symptoms

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

Most 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

What to check, in order

Start with the simplest. You can tick off each step.

Read the codes with a hybrid-compatible scanner and write down the freeze frame data
Use the scanner to command the movement and compare the actual position with the requested one.
Make sure the battery cooling air intake is clean
Check the 12 V auxiliary battery, which can also trigger warnings
Leave any high-voltage measurements to a specialized repair shop

Good to know

It can trigger limp mode.
It affects emissions.

What each character of P0DD9 means

P: Powertrain: engine and transmission
0: Generic code: same on every make
D: Subsystem depends on the code range
D9: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0DD9?

If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.

What causes code P0DD9?

The most common causes are: 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.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.