What it means
The control module detects phase V 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
Phase V is one of the electrical phases that turns the electric or auxiliary transmission-fluid pump motor. P0B05 sets when phase-V current is higher than expected, which can result from a shorted phase-V wire or winding, a pump that is binding, or a current-sensing fault.
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
- Check freeze-frame data and related pump codes to determine when the high phase-V current was recorded.
- Compare live phase-V current with phases U and W during the specified pump operation to confirm which phase is drawing excess current.
- Inspect the phase-V harness and pump connector for pinched insulation, shorts, melted sections, or damaged terminals.
- Following service safety procedures, check the pump motor for binding and test phase-V wiring for shorts.
- If wiring and pump movement are normal, test the motor winding and current-sensing or control circuit against the manufacturer's specifications.
Common fixes
- Repair shorted or pinched phase-V wiring and replace damaged connector terminals.
- Replace the pump motor if a shorted winding or binding pump is confirmed.
- Repair the current-sensing circuit if it reports excessive current inaccurately.
- Repair the pump control circuit if testing confirms it is driving phase V incorrectly.
Can I keep driving?
Do not continue driving with abnormal shifting, limited transmission operation, or limp mode; excessive phase-V current can overload the pump and affect fluid circulation. Stop safely if transmission behavior changes.
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.