What it means
The BMS detects a circuit range/performance fault on voltage sense channel L 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 BMS measures a battery cell group through voltage sense channel L and checks that the reading stays within its expected range and performance window. This code sets when channel L's reading is out of that window, such as from drift or excess resistance, rather than simply being flagged as low or high.
Common causes
Most likely first.
- Sense voltage drifted
- High-resistance contact
- Sensor element aged beyond calibration window
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 compare live channel L voltage with neighbouring channels for a persistent offset or drift.
- With the vehicle powered down following the manufacturer's high-voltage safety procedure, inspect channel L wiring and connectors for corrosion, looseness, or damage that could add resistance.
- Review channel L readings during charging or operation against adjacent cell groups, following manufacturer diagnostic guidance.
- Have a qualified hybrid/EV technician measure channel L circuit resistance and signal against manufacturer specifications.
- If the signal path passes, have the BMS channel L measurement input and calibration checked before replacing a sensing component or module.
Common fixes
- Clean and secure a high-resistance channel L connector.
- Repair or replace damaged channel L wiring that causes voltage drop or drift.
- Replace a channel L sensing component if testing confirms it has aged out of calibration.
- Replace a faulty BMS only after channel L wiring and calibration checks pass.
Can I keep driving?
A channel L reading outside its expected performance range can cause the BMS to reduce power or restrict charging. Avoid relying on full electric range or demanding trips until diagnosed, because continued operation with an unreliable cell-group reading may trigger further restrictions.
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.