P28E3: Shift Motor Phase U-V-W Performance

What it means

The phase currents of the shift motor do not match the commanded commutation pattern within tolerance. Sensor or driver synchronisation off.

At a glance

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

How it works

The transmission module commands a commutation pattern across the shift motor's U, V, and W phases and monitors phase current and rotor position to track motor movement. This code sets when the measured phase behavior does not match the commanded pattern, which can result from rotor position offset or an imbalance between phase currents.

Common causes

Most likely first.

1. Rotor position sensor offset
2. Phase current imbalance

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. Review freeze-frame data and live shift motor command, rotor position, and phase current information to identify when the pattern becomes implausible.
2. Check for related shift motor or position sensor codes that may explain the mismatch before testing individual phases.
3. Inspect the U, V, and W wiring, motor connector, and rotor position sensor connections for damage, looseness, or corrosion.
4. Check phase circuit continuity and sensor signals against the manufacturer's specification, comparing all three phases for an imbalance.
5. If the wiring is sound, follow the manufacturer's procedure to evaluate rotor position alignment and shift motor driver synchronization, then verify operation after repair.

Common fixes

• Repair damaged or loose phase wiring and connector terminals.
• Repair a poor connection in the rotor position sensor circuit.
• Correct rotor position sensor alignment or offset using the specified procedure.
• Repair or replace a shift motor or driver component confirmed to cause phase current imbalance.

Can I keep driving?

If shifts are erratic, slipping, or the vehicle is in limp mode, avoid driving because the module cannot reliably coordinate shift motor movement. If symptoms are mild, keep driving to a minimum and avoid hard acceleration or heavy loads.