P28E2: Shift Motor Phase U-V-W Circuit/Open

What it means

The output stage for the shift motor cannot drive current through at least one of the U/V/W phases. Open wire or open winding.

At a glance

• Usually lights the check-engine light
• The engine or gearbox may go into limp mode

How it works

The shift motor's U, V, and W phases carry the current needed to move the transmission gear actuator. This code sets when the module cannot drive current through at least one phase, pointing to an open phase wire, open motor winding, or a terminal that has backed out of its connector.

Common causes

Most likely first.

1. Open phase wire
2. Open motor winding
3. Pin pushed back out of connector body

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

1. Save freeze-frame data and shift motor commands, and note which attempted shift coincided with the fault.
2. Inspect the shift motor connector and U, V, and W harness for a backed-out pin, broken wire, corrosion, or damaged insulation.
3. Check continuity through each phase wire and connector terminal against the manufacturer's specification to locate an open circuit.
4. If the harness and terminals are intact, test the shift motor windings using the manufacturer's procedure to check for an open winding.
5. Repair the open circuit or replace the failed motor as indicated, then confirm that commanded shifts complete without the code returning.

Common fixes

• Seat and secure a backed-out U, V, or W connector pin.
• Repair a broken or open phase wire.
• Clean or replace damaged phase connector terminals.
• Replace the shift motor if a winding is confirmed open.

Can I keep driving?

If the transmission cannot shift reliably or is locked in one gear, do not continue a normal drive; the actuator may be unable to select or hold the requested gear. Move only as needed to reach a safe place and arrange diagnosis.