What it means
The output stage for the clutch B BLDC motor reports a high phase voltage on at least one of the U/V/W phases. Short to B+ or interrupted load.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Clutch B is operated by a brushless motor whose controller switches current through the U, V and W phase wires. The transmission control module monitors the phase output while driving the motor and sets this code when at least one phase reads higher than expected, which can happen with a short to battery voltage or an open load.
Common causes
Most likely first.
- Phase wire shorted to B+
- Open motor winding
- Connector pins corroded - high contact resistance
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
How to diagnose it
- Use a scan tool to record freeze-frame data and check clutch B motor commands and related fault codes to see when the high-phase condition occurred.
- With the vehicle safely parked, inspect the clutch B motor connector and U, V and W wiring for chafing, heat damage, corrosion or fluid intrusion that could connect a phase to battery voltage.
- Check connector fit and pin condition, including whether any terminal is pushed back, loose or corroded enough to create high resistance.
- With power isolated according to the manufacturer's procedure, test each phase wire for a short to battery supply and check continuity from the controller connector to the motor.
- Measure the clutch B motor winding paths and compare them with the manufacturer's specification to identify an open winding.
Common fixes
- Repair damaged U, V or W wiring that is shorted to battery voltage.
- Clean or repair corroded, loose or pushed-back connector terminals.
- Repair an open phase wire between the controller and clutch B motor.
- Replace the clutch B motor if a winding is open.
Can I keep driving?
Avoid driving if shifts are harsh, slipping or delayed, or if the transmission has entered limp mode; loss of clutch B control can leave the vehicle in an unsuitable gear. If the vehicle still moves normally, limit driving to a short trip for diagnosis and stop if shifting worsens.
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.