What Does P0B05 Mean?
The auxiliary transmission fluid pump motor control module has detected excessive current in the Phase V motor winding. Overcurrent on a single phase points to a winding short, wiring short, or mechanical binding. This condition can rapidly overheat the motor winding and the control module driver transistor, potentially causing permanent damage to the pump assembly and associated electronics.
Safety Warning
Overcurrent conditions pose a risk of overheating and potential fire hazard at the motor or controller. The system will disable the pump as a protective measure. Without the auxiliary pump, EV mode and auto-stop functionality are lost. Diagnose and repair promptly. If you detect any burning smell from the transmission area, cease driving immediately and have the vehicle towed.
Common Causes
35%
Shorted turns in the Phase V motor winding reducing impedance
25%
Phase V wiring shorted to chassis ground or another phase conductor
20%
Mechanical seizure or excessive friction in the pump increasing motor load
15%
Control module Phase V high-side or low-side MOSFET shorted
5%
Contaminated or water-damaged motor causing insulation breakdown
Diagnostic Steps
1
Monitor Phase V current draw in comparison to Phase U and Phase W with the scan tool. Confirm Phase V is drawing significantly more current than the other phases.
2
Disconnect the pump motor and measure Phase V winding resistance. Compare to Phase U and Phase W — Phase V should not be significantly lower. Also measure insulation resistance from Phase V to the motor housing (should exceed 1M ohm).
3
Check Phase V wiring for insulation damage, pinch points, or contact with sharp edges or hot surfaces. Measure insulation resistance from Phase V to ground and to each other phase wire.
4
Check for mechanical binding by attempting to manually rotate the pump (if accessible). A seized pump creates overcurrent across all phases, but a partially binding pump may stress one phase more.
5
Inspect the motor and all connectors for evidence of overheating, including discolored terminals, melted insulation, or burn marks. Check for water intrusion around the motor housing seal.
Estimated Repair Cost
$400 - $2,000
Parts + labor, varies by vehicle and location
The auxiliary transmission fluid pump motor control module has detected excessive current in the Phase V motor winding. Overcurrent on a single phase points to a winding short, wiring short, or mechanical binding. This condition can rapidly overheat the motor winding and the control module driver tr...
The most common cause of P0B05 (Auxiliary Transmission Fluid Pump Motor Phase V Current High) is: Shorted turns in the Phase V motor winding reducing impedance
Typical repair costs for P0B05 range from $400 to $2,000, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Overcurrent conditions pose a risk of overheating and potential fire hazard at the motor or controller. The system will disable the pump as a protective measure. Without the auxiliary pump, EV mode and auto-stop functionality are lost. Diagnose and repair promptly. If you detect any burning smell from the transmission area, cease driving immediately and have the vehicle towed.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0B05 to identify the root cause.
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Quick Info
Category
Powertrain
System
Hybrid Transmission Auxiliary Systems
Difficulty
Type
Generic (SAE)
Recommended Tools
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