P0B03

Code

Generic P — Powertrain

Electric/Auxiliary Transmission Fluid Pump Motor Phase V Current

Brand: Generic

Type: P — Powertrain

Views: UK: 29 EN: 44 RU: 28

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Page language: EN

Damaged, corroded or loose wiring/connectors to the pump (open, short to ground or short between phases)
Failed or shorted pump motor windings or internal motor electronics
Faulty motor drive / inverter or transmission control module (TCM) output stage
Mechanical seizure, hydraulic restriction or binding in the pump increasing current draw
Low or unstable battery/charging system voltage under load
Intermittent connector contact or water/contaminant intrusion

Read DTCs and freeze-frame/live data from the transmission/vehicle controller
Check battery voltage and charging system under load (engine off and cranking/engine on)
Visually inspect pump connector and harness for corrosion, heat damage, pin push-out or water intrusion
Backprobe pump power/phase pins and monitor voltage while commanding pump ON
Measure phase currents with a DC clamp meter or current probe; compare all phases for balance
Measure DC resistance between motor phases and between each phase and ground (looking for shorts or opens)

Nominal system voltage: 12–14.4 V (vehicle battery/charging system)
Typical running phase current (generic): ~5–30 A per phase (vehicle dependent)
Typical inrush/starting current: brief spikes up to 50–120 A (milliseconds) depending on motor size
Fault thresholds (generic): phase current = 0 A (open), sustained >80–100 A (overcurrent), phase-to-phase imbalance >25–35%
Expected control signal: PWM motor drive switching at inverter frequency (kHz range); controller reports averaged DC phase currents
Recommended measurement sampling: >=1 kHz for current probe/oscilloscope to capture inrush and PWM characteristics

Retrieve stored codes and freeze-frame data from the transmission control module; record battery voltage and reported pump parameters.
Verify battery state of charge and charging system (alternator) voltage; ensure battery can supply high current loads.
Perform a careful visual inspection of the pump harness and connector. Look for corrosion, bent pins, heat damage, melted insulation or water ingress.
With connector accessible and vehicle safe, backprobe the pump connector. Command the pump ON via bi-directional control or ignition cycle and verify presence of proper supply voltage to power/phase pins.
Measure phase currents using a DC clamp meter around each phase conductor while commanding pump operation. Compare phases for balance and watch for excessive sustained current or abnormal inrush.
Measure DC resistance between motor phases (phase-to-phase) and from each phase to ground. An open circuit, very high or very low resistance indicates winding open or short.