P28C8

Code

Generic P — Powertrain

Clutch A Pump Motor Performance

Brand: Generic

Type: P — Powertrain

Views: UK: 19 EN: 31 RU: 22

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Page language: EN

Causes

Open or short in pump motor power or ground circuit
Corroded, loose or damaged connector or wiring harness
Failed pump motor (internal winding or brush failure)
Faulty pump motor driver or control module output (PWM/driver transistor)
Low battery or supply voltage under load
Blown fuse or faulty relay feeding the pump motor

Symptoms

Malfunction Indicator Lamp (MIL) or warning message illuminated
Clutch A fails to engage or disengage properly
Reduced or no hydraulic pressure at clutch A
Erratic clutch engagement or slipping
Audible whining or no sound from pump when commanded
Transmission/shifting faults or limp mode may occur

What to check

Read stored freeze-frame data and related codes with a scan tool; note operating conditions
Visually inspect wiring harness and connector at the pump motor for corrosion, damage or looseness
Verify battery/resting voltage and voltage under cranking/operation
Check relevant fuses and relays for continuity and proper operation
Backprobe motor connector while commanding pump ON; observe voltage, PWM duty cycle and presence of ground
Measure pump motor resistance (ohms) with connector disconnected and compare to service spec

Signal parameters

Command signal: PWM duty cycle (%) from control module
Motor terminal voltage (V) while commanded
Motor current draw (A) under load
Motor winding resistance (Ω) at room temperature
PWM frequency (Hz) if applicable
System/battery voltage (V) during test

Diagnostic algorithm

Retrieve DTCs and freeze-frame data. Record related codes and conditions. Clear codes and attempt to re-create the fault. 2) Perform a visual inspection of pump motor connector, wiring harness, fasteners and ground points; repair obvious damage. 3) Check battery/resting voltage and measure voltage while commanding the pump; verify fuse and relay feeding the pump. 4) With ignition/key in run and pump commanded ON, backprobe the motor connector: verify command PWM/voltage from control module and a proper ground path. 5) Disconnect motor and measure winding resistance; compare to specification. 6) Measure current draw with motor connected while commanded; high current suggests mechanical/hydraulic binding or short, zero/current too low suggests open circuit or failed motor. 7) If electrical control signals are present but motor does not run, bench-test or replace the pump motor. If motor runs on bench but not in-vehicle, trace wiring for intermittent opens/shorts or poor ground. 8) If motor runs but clutch pressure is low, inspect hydraulic lines, filter, fluid level and clutch actuator for restrictions or leaks. 9) If control module output is absent or abnormal and wiring is good, test or replace the driver module or control module per manufacturer procedures. 10) After repair, clear codes and perform functional test under the same conditions to confirm repair. Note: always follow safety procedures — support vehicle, relieve hydraulic pressure per procedure and disconnect battery when required.

Likely causes

Pump motor electrical failure (most common)
Damaged/loose connector or poor ground
Fuse, relay or supply voltage issue
Control module output driver fault
Hydraulic restriction or seized pump

Fault status

⚠️ Status

P28C8 — Clutch A Pump Motor Performance: control module detected pump motor performance out of expected range (electrical, mechanical or hydraulic fault).

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours