What Does P0C22 Mean?
DTC P0C22 indicates that the three-phase motor circuit (U, V, W) of the auxiliary transmission fluid pump is reading abnormally high voltage. This over-voltage condition on the pump motor phases can occur from a failed high-side driver in the pump controller, back-EMF spikes from the motor, or a supply voltage issue. The pump controller will shut down to protect itself and the motor from damage due to the excessive voltage condition.
Common Causes
30%
Failed high-side MOSFET in the pump controller (stuck on or leaking)
20%
Supply voltage to the pump controller exceeding specification
20%
Back-EMF voltage spikes from pump motor deceleration without proper clamping
15%
Open or high-resistance ground connection at the pump motor
15%
Faulty phase voltage sensing circuit in the pump controller
Diagnostic Steps
1
Step 1: Check for companion DTCs P0C20 (open) and P0C21 (low). Review freeze-frame data for the supply voltage to the pump controller and the operating state at time of fault.
2
Step 2: Verify the supply voltage to the auxiliary pump controller is within specification. An over-voltage from the vehicle's 12V or 48V system (depending on architecture) can cause phase over-voltage.
3
Step 3: Inspect the pump motor ground connection for corrosion, looseness, or high resistance. A poor ground can cause voltage to float high on the phase circuits.
4
Step 4: Disconnect the pump motor and check the controller output voltages. If the controller is outputting voltage with no motor connected, a high-side MOSFET may be stuck on.
5
Step 5: If supply voltage and ground are normal, and the controller outputs are abnormal, replace the auxiliary pump controller module. If the pump motor is causing back-EMF issues, replace the pump assembly.
Estimated Repair Cost
$350 - $2,200
Parts + labor, varies by vehicle and location
DTC P0C22 indicates that the three-phase motor circuit (U, V, W) of the auxiliary transmission fluid pump is reading abnormally high voltage. This over-voltage condition on the pump motor phases can occur from a failed high-side driver in the pump controller, back-EMF spikes from the motor, or a sup...
The most common cause of P0C22 (Auxiliary Transmission Fluid Pump Phase U-V-W Circuit High) is: Failed high-side MOSFET in the pump controller (stuck on or leaking)
Typical repair costs for P0C22 range from $350 to $2,200, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Over-voltage on the pump motor circuit can damage the controller and potentially cause the pump to run uncontrolled or fail entirely. Loss of auxiliary pump function compromises transmission lubrication and hydraulic pressure during EV operation.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0C22 to identify the root cause.
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Quick Info
Category
Powertrain
System
Hybrid/EV Transmission Auxiliary Pump
Difficulty
Type
Generic (SAE)
Recommended Tools
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