Auxiliary Transmission Fluid Pump Motor Phase U Circuit Malfunction
The P0B00 code indicates a problem with the phase U circuit of the auxiliary transmission fluid pump motor. This pump is typically found in hybrid or electric vehicles to circulate transmission fluid when the main engine is off. The issue may be due to an open or short circuit in the motor windings, a faulty motor, or a problem with the pump control module. This can lead to inadequate transmission fluid circulation, potentially causing transmission overheating or damage.
01. Most Common Causes
- Open or short circuit in the auxiliary transmission fluid pump motor phase U winding
- Faulty auxiliary transmission fluid pump motor
- Damaged wiring or connectors in the pump motor circuit
- Malfunctioning pump control module or transmission control module
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission overheating or slipping
- Reduced fuel economy in hybrid vehicles
- Transmission fluid leaks or unusual noises from the pump area
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to retrieve all stored codes and freeze frame data.
Step 2: Visually inspect the auxiliary transmission fluid pump and its wiring for damage, corrosion, or loose connections.
Step 3: Test the motor phase U circuit for continuity and resistance using a multimeter; compare to manufacturer specifications.
Step 4: If the motor tests faulty, replace the auxiliary transmission fluid pump motor.
Step 5: Clear the code and test drive to verify repair.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive with this code as it can lead to transmission overheating and potential failure, especially in hybrid vehicles that rely on the auxiliary pump for fluid circulation when the engine is off.
How much does it cost to fix?▼
The cost to fix P0B00 typically ranges from $50 to $150 for diagnosis and minor repairs like wiring fixes, but could be higher if the pump motor needs replacement, which can cost $200-$500 or more including labor.