What it means
The control module detects a fault related to current in phase V of the electric/auxiliary transmission fluid pump motor.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
The electric or auxiliary transmission-fluid pump motor has three phases, and phase V is one of the circuits that produces its rotation. P0B03 reports a phase-V current fault without specifying whether the current is high or low, so live data and circuit tests are needed to narrow it down.
Common causes
Most likely first.
- Pump motor or phase wiring fault
- Pump motor control or current-sensing fault
Symptoms
- Transmission or hybrid system warning light
- Transmission operation may be limited
How to diagnose it
- Save freeze-frame data and scan for pump, transmission, and hybrid codes to establish when the phase-V fault appeared.
- Compare live phase-V current with phases U and W during the pump operating conditions described in service information.
- Inspect the pump connector and phase-V wiring for loose terminals, corrosion, chafing, or heat damage.
- Test phase-V wiring continuity and isolation using the wiring diagram and the manufacturer's procedures.
- If the wiring checks out, test the pump motor and current-sensing or control circuit against the manufacturer's specifications.
Common fixes
- Repair a loose or corroded pump connector or damaged phase-V wire.
- Correct a verified phase-V wiring fault.
- Replace the pump motor if testing confirms a phase-related motor failure.
- Repair the current-sensing or pump-control circuit if it is responsible for the reading.
Can I keep driving?
Avoid driving if transmission operation is restricted, shifting is abnormal, or limp mode is active because pump performance may be compromised. If operation seems normal, limit use and arrange diagnosis soon.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.