What it means
The control module detects phase W current above the expected level in 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’s three-phase motor circulates fluid for transmission hydraulic pressure. The control module monitors phase W current and sets P0B08 when it rises above the expected level, which can point to a shorted winding or wiring, or a motor that is binding.
Common causes
Most likely first.
- Shorted phase wiring or motor winding
- Pump motor binding or stalled
- Current sensing or control fault
Symptoms
- Transmission or hybrid system warning light
- Transmission operation may be limited
How to diagnose it
- Capture freeze-frame data and scan for other pump or transmission codes to see whether the high phase W current occurred during startup or pump operation.
- Review available scan-tool phase-current data and compare phase W with the other phases under matching conditions.
- With the system made safe according to service information, inspect phase W wiring and pump connectors for chafing, melted insulation, fluid intrusion, or terminals touching.
- Test the phase W circuit for shorts to power or other phases, and check the motor winding as directed by the manufacturer’s procedure and specification.
- If the circuit is intact, check whether the pump motor is binding or stalled and verify the current-sensing and control electronics.
Common fixes
- Repair phase W wiring shorted to power or another motor phase.
- Replace damaged or overheated pump connector terminals.
- Replace the pump motor if a winding fault or binding is confirmed.
- Repair the current sensor or pump control module if it is producing a false high-current reading.
Can I keep driving?
Avoid driving if the transmission is slipping, shifting harshly, or entering limited operation, since an overloaded or stalled pump can compromise fluid circulation. If the warning is present but operation seems normal, keep the trip short and gentle and arrange prompt diagnosis.
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.