What it means
The BMS detects a circuit high 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 cell-group voltage through channel U, one of the battery's individual sense paths. This code sets when the channel U signal is higher than its expected range, leaving the BMS unable to rely on that cell-group reading.
Common causes
Most likely first.
- Sense wire shorted to higher voltage
- Reference regulator overvoltage
- 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 live channel U voltage with adjacent cell-group readings to see whether the high signal is steady or tied to a particular operating condition.
- With the vehicle powered down under the manufacturer's high-voltage safety procedure, inspect channel U's sense wire for damage or contact with a higher-voltage conductor.
- Inspect channel U connector pins for corrosion, looseness, or poor contact that could distort the signal.
- Have a qualified hybrid technician test channel U for shorts to higher voltage and verify its reference supply against the manufacturer's specification.
- If the wiring and reference are correct, test the battery monitoring module's channel U input using the manufacturer's procedure.
Common fixes
- Secure the channel U harness if it is contacting another conductor.
- Clean or repair corroded or loose channel U connector pins.
- Repair or replace channel U wiring shorted to a higher-voltage circuit.
- Repair the reference supply or replace the battery monitoring module only if tests identify it as the cause.
Can I keep driving?
Limit driving and avoid hard acceleration because power may be reduced or restricted unexpectedly; charging may also fail or slow. Stop if a battery safety warning appears and arrange prompt diagnosis.
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.