What it means
The BMS detects a circuit range/performance fault on voltage sense channel U 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 uses channel U to measure a cell group's voltage and checks whether the reading behaves within its expected range over time. This code sets when the channel U reading is present but outside the expected range or performance window, which can happen with voltage drift or high contact resistance.
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 channel U's live reading with adjacent cell-group voltages over changing battery load to see whether the discrepancy persists.
- With the vehicle safely powered down under the manufacturer's high-voltage procedure, inspect channel U's connector and wiring for corrosion, looseness, or damage that could add resistance.
- Check the channel U connector pin fit and contact condition, since a high-resistance connection can make the reading drift under load.
- Have a qualified hybrid technician measure the channel U circuit and connections against the manufacturer's specification under the specified conditions.
- If wiring and contacts pass, test the channel U sensing input and calibration status using the manufacturer's service procedure.
Common fixes
- Reseat the channel U connector if its contact is loose.
- Clean or repair channel U pins with corrosion or high contact resistance.
- Repair or replace channel U wiring with excessive resistance or damage.
- Replace the affected sensing or monitoring component only if testing confirms drift beyond the manufacturer's calibration limits.
Can I keep driving?
Avoid heavy acceleration and long trips while the BMS is limiting power, and do not assume the displayed electric range is reliable. Have the channel U reading checked promptly because continued charging or use may be restricted.
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.