P0B01

Code

Generic P — Powertrain

Electric/Auxiliary Transmission Fluid Pump Motor Phase U Current Low

Brand: Generic

Type: P — Powertrain

Views: UK: 19 EN: 40 RU: 24

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Page language: EN

Open or high-resistance wiring in phase U (broken conductor, corrosion, connector fault)
Faulty motor windings (open or shorted turn in phase U)
Faulty inverter/driver power MOSFET/IGBT for phase U
Short to supply or ground limiting current flow
Poor power supply or battery voltage causing reduced drive current
PCM/TCM/ECU driver software or internal fault (incorrect current sensing)

Retrieve freeze frame and related codes from scan tool
Visually inspect harness, connectors and pins for damage, corrosion, or loose terminals at pump, inverter/driver, and control module
Check battery voltage and main power/ground integrity with engine off and during cranking/running
Measure DC resistance between motor phases (U-V, V-W, W-U) and compare for imbalance
Check for continuity between phase U conductor and motor terminal; check for shorts to ground or battery
Use a current clamp to measure phase currents during pump operation

Expected phase current (running/load): varies by vehicle — typically in the single to tens of amps; phase U should be similar to V and W (no large imbalance)
Phase-to-phase resistance: phases should be similar (typical small ohm range; large differences indicate winding fault)
Phase-to-ground resistance: very high/open (no short to ground)
PWM frequency: typically 1–20 kHz depending on manufacturer; duty cycle varies with commanded pump speed
Supply voltage to inverter: battery voltage (~12–15 V) with minimal voltage drop under load

Obtain all related codes and freeze-frame data; note conditions when code set
Perform a thorough visual inspection of connectors, pins, and harness between pump motor and inverter/driver; repair any physical damage
Check battery and main power/ground connections; ensure proper charging system operation
With service manual wiring diagrams, verify continuity and resistance of phase U conductor and compare to the other phases
Measure motor winding resistances: compare U-V, V-W and W-U. If one phase differs significantly, suspect motor winding fault
With vehicle safely supported and controls available, command pump ON and measure phase currents with a clamp meter; compare three phases for imbalance
If currents are low on all phases, check power supply and driver enabled status; if only U is low, suspect driver or wiring to U
If wiring checks good, scope the inverter output during operation: verify PWM on all three outputs and expected voltage swings; absence or incorrect waveform on U indicates inverter transistor failure
If inverter/driver is separate from control module and swap/testing possible, swap driver channels or perform module bench test per manufacturer procedures
If motor winding identified faulty, replace pump assembly. If inverter/driver or control module fault found, replace or repair per service procedures and reprogram if required
Clear codes and road-test to confirm repair; monitor for recurrence