A shorted or partially shorted phase U winding inside the electric transmission fluid pump motor; Damaged or chafed wiring between the TCM and the pump connector, causing a short to ground or power on the phase U circuit; Corrosion or loose pins in the pump electrical connector, raising resistance and current draw; A failing pump driver circuit inside the TCM or power control module, delivering incorrect voltage to phase U; Mechanical binding or debris inside the pump, forcing the motor to draw higher current to turn; Low or contaminated transmission fluid that increases pump load and current draw; A defective pump control module or integrated power inverter that misreads or misapplies phase current

DTC codes / P0Bxx · Hybrid propulsion / P0B02

P0B02Electric/Auxiliary Transmission Fluid Pump Motor Phase U Current High

P0B02 indicates that the electric or auxiliary transmission fluid pump motor has drawn excessive current on phase U, which the transmission control module (TCM) monitors to protect the pump and wiring. The TCM compares commanded pump operation against measured current and flags this code when phase U current exceeds the calibrated threshold for a set time.

SystemPowertrain

Code typeGeneric (all makes)

SeverityHigh

Fix difficultyProfessional

AreaHybrid propulsion

Symptoms you may notice

Illumination of the check engine light or transmission warning lamp, often with no other symptoms besides the warning light
Harsh or delayed shifting, or the transmission entering limp mode with reduced power
Overheating of the transmission fluid during low-speed or stop-and-go driving if the auxiliary pump fails to circulate fluid
A whining or buzzing noise from the transmission area when the pump is commanded on
Inability to select certain gears or a sudden loss of propulsion in hybrid or electric vehicles that rely on the pump for clutch actuation

Common causes, most likely first

A shorted or partially shorted phase U winding inside the electric transmission fluid pump motor
Damaged or chafed wiring between the TCM and the pump connector, causing a short to ground or power on the phase U circuit
Corrosion or loose pins in the pump electrical connector, raising resistance and current draw
A failing pump driver circuit inside the TCM or power control module, delivering incorrect voltage to phase U
Mechanical binding or debris inside the pump, forcing the motor to draw higher current to turn
Low or contaminated transmission fluid that increases pump load and current draw
A defective pump control module or integrated power inverter that misreads or misapplies phase current

How to diagnose and fix it

Scan all modules for stored and pending codes, and record freeze-frame data for P0B02 to see the conditions when it set
Inspect the pump electrical connector and harness for corrosion, chafing, or loose pins, and repair any damage found
Measure resistance and insulation on phase U of the pump motor and compare it to the other phases and to manufacturer specifications
Check transmission fluid level and condition, and top up or replace fluid if it is low or contaminated
Command the auxiliary pump on with a scan tool and measure current draw with a clamp meter to confirm excessive current on phase U
If current is high with good wiring, remove and bench-test the pump motor, or replace the pump if windings or bearings are faulty
If the pump and wiring test good, diagnose the TCM or pump control module driver circuit and replace the module if it is internally shorted

What the pump current code really means

A high current reading on phase U does not always mean the pump motor is bad; a chafed harness shorting to ground can produce the same code and is far cheaper to fix.
Technicians often replace the pump only to find the TCM driver circuit was the real fault, so always verify current at the pump connector before condemning the motor.
Low transmission fluid or a clogged filter can raise pump current enough to set P0B02, especially on units where the auxiliary pump runs continuously at low speed.
On hybrid and electric vehicles, the auxiliary pump may only run during engine stop or low-speed operation, so the code may not set during a short test drive.
P0B02 can be stored alongside phase V or W current codes if the fault is in the shared power supply or ground, so check all related codes before diagnosing a single phase.

Can I keep driving with P0B02?

Limit driving to a short distance to a repair shop, because a failed auxiliary pump can cause transmission overheating or loss of propulsion in hybrid and electric vehicles. Avoid heavy loads, stop-and-go traffic, and high ambient temperatures until the fault is repaired.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.