What it means
The cell balancing circuit H reports a stuck on condition. Cell-group voltage equalization may be impaired on this channel.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Balancing circuit H controls a switching path the BMS uses to reduce charge differences in its assigned cell group. The BMS checks that this path turns off when required; this code sets when the H channel remains active, which can be caused by a stuck switch, shorted wiring, or a failed driver.
Common causes
Most likely first.
- Balancing switch or driver stuck on
- Shorted balancing-circuit wiring
- BMS driver fault
Symptoms
- EV/hybrid system warning light on
- Reduced power output or limp mode
- Charging may fail or be slowed
- Reduced electric range
How to diagnose it
- Capture freeze-frame data and live H-channel status to establish when the BMS expected balancing to stop and the cell-group voltage and temperature at that time.
- Compare the H group with other groups and confirm whether balancing was still being commanded under those conditions.
- With the high-voltage system made safe using the vehicle’s procedure, inspect H-channel wiring and connectors for shorts, damage, or contamination.
- Test whether the H switching path remains conductive when it should be off, following the manufacturer’s procedure and specification.
- If the switch and wiring pass, test the BMS driver that controls circuit H.
Common fixes
- Repair a short or damaged H-channel connector.
- Repair shorted wiring in the H-channel harness.
- Replace an H balancing switch confirmed stuck on.
- Repair or replace the BMS if its H-channel driver is stuck on.
Can I keep driving?
Limit driving and avoid charging until the fault is assessed because a path that stays on can worsen imbalance in the H cell group. Stop if power is reduced or a battery warning appears, and have the high-voltage system inspected promptly.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.