P28E2

Code

Generic P — Powertrain

Shift Motor Phase U-V-W Circuit/Open

Brand: Generic

Type: P — Powertrain

Views: UK: 33 EN: 63 RU: 41

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Page language: EN

Causes

Open or broken wiring in one or more phase conductors (U, V, W).
Corroded, loose, or damaged connector(s) at motor or control module.
Internal motor winding open (motor failure).
Failed motor driver or power electronics in transmission/shift control module.
Blown fuse, tripped relay, or loss of battery power to motor drive.
Mechanical seizure or heavy binding causing driver overcurrent and damage.

Symptoms

Shift actuator does not move or moves intermittently.
Transmission or gear selection errors; inability to change gears.
Transmission warning/Service light or MIL illuminated.
Stored DTC(s) and possible limp-home or reduced functionality.
Unusual motor noise or no motor sound when commanded.

What to check

Retrieve all stored and pending DTCs and freeze frame data.
Visually inspect motor, connectors, and wiring harness for damage, corrosion, or pinched areas.
Verify proper battery voltage at motor power supply fuse/relay.
Check fuses and relays related to transmission/shift motor power.
Backprobe motor connector and measure phase-to-phase and phase-to-ground continuity with ignition OFF.
With actuator commanded, backprobe control module outputs to verify PWM signals and voltage using a scope or lab-grade meter.

Signal parameters

Phase-to-phase resistance: low ohms (typically a few ohms; exact value depends on motor design).
Phase-to-ground: open/infinite (no continuity) expected. Any measurable continuity indicates short to ground.
Battery supply voltage at motor power feed: ≈12 V (vehicle nominal) with ignition ON.
PWM drive present on phase outputs when motor commanded (frequency depends on manufacturer; often hundreds to thousands of Hz).
Motor current draw: low when free-running, rises if motor is stalled or binding (use clamp meter).
No large, sustained voltage drop on supply during commands (significant drop indicates short/high current).

Diagnostic algorithm

Read and record all DTCs, freeze frame, and related transmission codes; note conditions when the code set.
Visually inspect motor, connector, and wiring for damage, corrosion, or water intrusion; repair any obvious faults.
Check and verify fuses and relays for the motor power circuit; replace if faulty.
With ignition OFF, disconnect motor connector and measure resistance between U-V, V-W, and U-W (expect low and similar ohms); record values. Also check each phase to vehicle ground (expect open).
If a phase shows open or very high resistance, inspect harness for breaks and repair wiring. If wiring is intact, suspect internal motor winding failure.
Reconnect and backprobe control module outputs. Command the motor (diagnostic tool or scan tool) while monitoring for PWM signals and voltage on each phase. Use an oscilloscope if available.
If controller outputs are present but motor phases open at the motor connector, replace/repair the motor. If outputs are absent or abnormal, diagnose/replace the control module or driver circuitry.
If intermittent, perform wiggle tests on harness and connectors while commanding motor; repair any intermittent connections.
After repairs, clear codes and perform functional test and road test to confirm proper operation and that the DTC does not return.

Likely causes

Broken conductor or pinched harness between control module and shift motor.
Corroded terminals or water intrusion at the motor connector.
Open motor phase due to internal winding break.
Defective MOSFETs/transistors in the motor driver circuit of the control module.
High resistance connection or poor ground causing intermittent open detection.

Fault status

⚠️ Status

Control module detected open circuit/loss of continuity in one or more shift motor phases (U, V, W). Motor may be unresponsive or unable to complete commanded shift.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours