What it means
The BMS detects a circuit high fault on voltage sense channel Q 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 battery management system monitors a cell-group voltage using sense channel Q and checks that the signal stays within its expected range. This code sets when the Q signal is too high, so the module cannot trust that battery measurement.
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 Q voltage with adjacent cell-group readings to verify that the high signal is not a brief operating-condition effect.
- With the vehicle powered down as specified by the manufacturer, inspect channel Q wiring for damaged insulation or contact with a higher-voltage circuit.
- Have a qualified hybrid technician test channel Q for a short to a higher-voltage source using the manufacturer's isolation and testing procedures.
- Inspect channel Q connector pins for corrosion or looseness and check contact resistance against the manufacturer's specification.
- If the wiring and connector are sound, test the reference regulator and battery monitoring module for an overvoltage fault using the manufacturer's procedure.
Common fixes
- Repair channel Q wiring that is shorted to a higher-voltage circuit.
- Clean or repair corroded or loose channel Q connector terminals.
- Repair the reference regulator if testing confirms that it is supplying excessive voltage.
- Repair or replace the battery monitoring module if its channel Q input is faulty.
Can I keep driving?
Limit driving and avoid long trips or heavy acceleration because the system may reduce power or enter limp mode. Charging can also be limited or fail while the channel Q reading is unreliable, so arrange prompt diagnosis by a qualified hybrid technician.
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.