P0C22

Code

Generic P — Powertrain

Electric/Auxiliary Transmission Fluid Pump Phase U-V-W Circuit High

Brand: Generic

Type: P — Powertrain

Views: UK: 28 EN: 40 RU: 22

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Page language: EN

Causes

Short to battery voltage on one or more pump phase wires
Faulty inverter / motor controller output stage
Damaged or corroded connector pins or wiring harness (chafing, melted insulation)
Internal short or damaged motor windings
Poor or missing ground connection to inverter or pump
Software/firmware or calibration error in transmission control module (TCM/PCM)

Symptoms

Transmission/shift warning lamp or message
Transmission fluid pump not running or low fluid pressure
Loss of hydraulic pressure / abnormal shifting or limp mode
Stored transmission or inverter-related DTCs
Unusual electrical smells or visible damage at connector
Intermittent operation of auxiliary pump

What to check

Read freeze-frame and full code list from transmission/vehicle modules; record related inverter or HV system codes
Visually inspect pump, connectors, and harness for damage, corrosion, heat/melt marks, or water ingress
Check for blown fuses, tripped contactors/relays, and integrity of high-voltage interlocks
Verify proper battery/DC bus voltage and charging system operation
Verify ground connections at inverter/module and transmission/pump
Use a scan tool to view inverter/pump status, commanded PWM/frequency, and measured phase values if available

Signal parameters

Balanced three-phase AC output from inverter to pump during operation — similar amplitude and phase relationship across U, V, W
Phase-to-phase and phase-to-ground voltages should follow manufacturer specification with no sustained DC offset
Waveform frequency and PWM duty should vary with commanded pump speed
Winding resistance (low-ohm) should be balanced between phases with no open or short to ground
No high steady DC voltage present on any phase conductor when pump is running

Diagnostic algorithm

Retrieve all related DTCs and freeze-frame data from TCM/PCM and inverter module. Note conditions when fault occurred.
Visually inspect high-voltage connectors, wiring harness routing, and pump assembly for damage, burns, water intrusion, or loose pins.
With vehicle powered down and HV system made safe per manufacturer procedures, disconnect pump motor harness and inspect connector terminals for corrosion or shorting.
Perform insulation/resistance checks: measure motor winding resistances (U-V, V-W, W-U) and resistance from each phase to chassis ground. Compare for balance and no shorts.
Check DC bus/high-voltage supply to inverter for correct voltage and integrity of fuses/contactors. Verify no unintended feed to phase conductors when off.
With appropriate HV safety measures and test equipment, measure phase voltages and waveforms at the inverter output while commanding pump on with a capable scan tool or oscilloscope. Look for DC offset, overvoltage, or missing phases.
Inspect and test inverter/controller output stage (power transistors) for failures — check MOSFET/IGBT driver signals and gate circuits if qualified to do so or refer to service procedures.
Repair or replace damaged wiring/connectors. If motor windings are shorted or inverter output transistors are faulty, replace the affected component per OEM guidance.
Clear codes and perform functional tests, verify pump operation, monitor live data for repeat faults, and ensure no residual errors; update controller software/calibration if recommended.

Likely causes

Wiring or connector short to battery or high-voltage bus (most common)
Failed inverter output transistor(s) or driver electronics
Damaged motor winding(s) or internal short in pump motor
Poor grounding or high-resistance ground connection
Controller fault or corrupted software/calibration (least common)

Fault status

⚠️ Status

High voltage/signal detected on one or more transmission pump phase circuits (U, V or W). Possible wiring short, inverter or motor fault preventing correct pump drive.

🔴 Repair difficulty: Hard

⏱️ Diagnostic time: 1.5-4.0 hours