What it means
The BMS detects a circuit low fault on voltage sense channel B of the high-voltage battery. Cell-group voltage measurement is unreliable on this channel.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
The high-voltage battery management system reads voltage from cell groups through sense channel B. This code sets when the channel’s signal is lower than the module expects, so the reported voltage for that group may not be trustworthy.
Common causes
Most likely first.
- Sense wire shorted to ground
- Open or high-resistance connection in the sense circuit
- Fault in the battery voltage-sensing module
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
- Save freeze-frame data and check live battery cell-group voltages for channel B and neighboring groups to see whether B reads unusually low or drops out.
- With the vehicle powered down according to the manufacturer’s high-voltage safety procedure, inspect channel B’s accessible sense wiring and connectors for damage, pinched insulation, corrosion, or a wire touching ground.
- Check the channel B connector seating and terminals for looseness or corrosion that could create an open or high-resistance path.
- Have a qualified technician test channel B continuity and for an unintended path to ground using the manufacturer’s procedure and specification.
- If the wiring and connections pass, compare the BMS readings and perform the manufacturer’s checks for the battery voltage-sensing module.
Common fixes
- Reseat and clean a loose or corroded channel B connector.
- Repair damaged channel B sense-wire insulation or wiring that is shorted to ground.
- Repair an open or high-resistance connection in the channel B sense circuit.
- Replace or repair the battery voltage-sensing module if testing confirms it is faulty.
Can I keep driving?
Avoid driving if the vehicle has reduced power, enters limp mode, or shows a high-voltage battery warning; an unreliable channel B reading can restrict propulsion or charging. Arrange prompt diagnosis, and do not access high-voltage battery wiring yourself.
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.