What Does P0B02 Mean?
The auxiliary transmission fluid pump motor control module has detected that the Phase U motor winding current exceeds the maximum expected value. Excessive current typically indicates a short circuit in the Phase U winding or its wiring, which can cause the motor to overheat, the control module driver to fail, or protective fuses to blow. The pump may operate erratically or not at all.
Safety Warning
Overcurrent conditions can cause overheating of the motor, wiring, or control module, creating a potential fire risk in extreme cases. The control module will typically disable the pump to protect itself. Without the auxiliary pump, transmission lubrication during EV mode and auto-stop is compromised. Have the vehicle diagnosed promptly; do not ignore burning smells near the transmission area.
Common Causes
35%
Phase U motor winding shorted turns (inter-turn short circuit)
25%
Phase U wiring shorted to ground or to another phase
20%
Pump motor mechanical seizure or excessive drag increasing current draw
15%
Control module Phase U MOSFET driver shorted, driving excessive current
5%
Water intrusion into the motor or connector causing partial short circuit
Diagnostic Steps
1
Monitor live data for Phase U current during pump operation. Compare with Phase V and Phase W — Phase U will show significantly higher current if the winding or wiring is shorted.
2
Disconnect the pump motor and measure Phase U winding resistance. A significantly lower resistance than Phases V and W indicates shorted turns in the Phase U winding. Also measure insulation resistance from Phase U to the motor case (should exceed 1M ohm).
3
With the motor disconnected, check Phase U wiring insulation resistance to ground and to the other phase wires. Any reading below 10K ohms indicates a wiring short that must be located and repaired.
4
Attempt to rotate the pump motor by hand (if accessible) to check for mechanical binding or seizure. A locked or stiff pump will cause overcurrent on all phases, not just Phase U.
5
Inspect the motor and connector for signs of water intrusion, overheating (discolored wires, melted insulation), or physical damage. Check connector seals and grommets for integrity.
Estimated Repair Cost
$400 - $2,000
Parts + labor, varies by vehicle and location
The auxiliary transmission fluid pump motor control module has detected that the Phase U motor winding current exceeds the maximum expected value. Excessive current typically indicates a short circuit in the Phase U winding or its wiring, which can cause the motor to overheat, the control module dri...
The most common cause of P0B02 (Auxiliary Transmission Fluid Pump Motor Phase U Current High) is: Phase U motor winding shorted turns (inter-turn short circuit)
Typical repair costs for P0B02 range from $400 to $2,000, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Overcurrent conditions can cause overheating of the motor, wiring, or control module, creating a potential fire risk in extreme cases. The control module will typically disable the pump to protect itself. Without the auxiliary pump, transmission lubrication during EV mode and auto-stop is compromised. Have the vehicle diagnosed promptly; do not ignore burning smells near the transmission area.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0B02 to identify the root cause.
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Quick Info
Category
Powertrain
System
Hybrid Transmission Auxiliary Systems
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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