What it means
The output stage for the shift 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
The transmission shift motor depends on its U, V, and W phase outputs to move the gear actuator. This code sets when the module detects an abnormally high voltage on at least one phase, which can indicate a phase wire shorted to battery voltage or an open motor winding interrupting the 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
- Capture freeze-frame data and shift motor commands, and note whether the fault appears during a particular gear selection.
- Inspect the U, V, and W phase harness and motor connector for rubbed-through insulation, corrosion, loose terminals, or signs of heat.
- With the circuit isolated as specified by the manufacturer, check each phase wire for a short to B+ and verify continuity through the harness.
- If the harness checks out, test the shift motor windings and driver outputs using the manufacturer's specification to identify an open load or output fault.
- Repair the confirmed short, open winding, or connector fault, then verify phase operation through commanded shifts.
Common fixes
- Clean and secure corroded phase connector pins.
- Repair a U, V, or W phase wire shorted to B+.
- Repair an open or damaged section of the phase wiring.
- Replace the shift motor if a winding is confirmed open.
Can I keep driving?
Avoid driving if shifts are missing, slipping, or the transmission has entered limp mode, since the shift motor may not move the actuator correctly. If the vehicle is stuck in a gear, arrange recovery rather than attempting a normal journey.
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.