What it means
The BMS detects a circuit low 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 measures a cell group's voltage through channel U. This code sets when the channel U signal falls below its expected range, so that group's voltage reading is unreliable and the vehicle may restrict battery power or charging.
Common causes
Most likely first.
- Sense wire shorted to ground
- Open in sense wire
- Connector pins corroded - high contact resistance
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 reported voltage with adjacent cell-group readings to confirm whether the low signal is persistent or intermittent.
- With the vehicle shut down under the manufacturer's high-voltage safety procedure, inspect channel U's sense wire for damage or contact with ground.
- Check the channel U connector for corrosion, loose pins, or incomplete seating that could pull the signal low.
- Have a qualified hybrid technician test channel U wiring for opens and shorts to ground following the manufacturer's procedure.
- If the wiring and connector pass, test the channel U input at the battery monitoring module against the manufacturer's specification.
Common fixes
- Reseat the channel U connector if it is loose.
- Clean or repair corroded channel U connector pins.
- Repair or replace channel U wiring that is open or shorted to ground.
- Replace or repair the battery monitoring module only if testing confirms an internal channel U fault.
Can I keep driving?
Avoid hard acceleration and long trips if power is limited; charging may be slowed or unavailable and the vehicle may enter limp mode. Arrange prompt diagnosis, and stop if a battery safety warning appears.
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.