Auxiliary Transmission Fluid Pump Motor Phase W Current High
The P0B08 code indicates that the Powertrain Control Module (PCM) has detected an abnormally high current draw on phase W of the auxiliary transmission fluid pump motor. This pump is typically used in hybrid or electric vehicles to circulate transmission fluid when the main engine is off. High current can be caused by a short circuit, a failing motor, or a stuck pump, leading to potential overheating and damage to the pump or control module.
01. Most Common Causes
- Short circuit in phase W wiring or connector
- Failing auxiliary transmission fluid pump motor
- Stuck or seized pump mechanism
- Faulty PCM or TCM (Transmission Control Module)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission overheating or poor shifting performance
- Reduced fuel economy in hybrid mode
- Auxiliary pump not operating when expected
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to confirm the code and check for related codes (e.g., P0B06, P0B07).
Step 2: Visually inspect the auxiliary pump wiring and connector for damage, corrosion, or loose pins.
Step 3: Measure resistance and continuity of phase W circuit between the pump and PCM; compare to specifications.
Step 4: Test the pump motor by applying battery voltage directly (if safe) to see if it runs smoothly.
Step 5: If wiring and motor are okay, suspect a faulty PCM/TCM and perform further diagnostics.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances, as high current can damage the pump or control module, potentially leading to transmission overheating or failure.
How much does it cost to fix?▼
Diagnosis typically costs $50-$150. Repair costs vary: wiring repair $100-$300, pump replacement $200-$600, PCM replacement $500-$1000.