Auxiliary Transmission Fluid Pump Motor Phase W Current Low
The P0B07 code indicates that the Powertrain Control Module (PCM) has detected a low current condition in phase W of the auxiliary transmission fluid pump motor. This pump is responsible for circulating transmission fluid to cool and lubricate the transmission, especially during start-stop events or when the engine is off. Low current in one phase suggests an electrical fault such as a damaged motor winding, poor connection, or a failing pump motor. If left unaddressed, it can lead to inadequate transmission cooling and potential transmission damage.
01. Most Common Causes
- Faulty auxiliary transmission fluid pump motor
- Open or shorted wiring in phase W circuit
- Poor electrical connection at pump motor connector
- Failed PCM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission overheating
- Reduced fuel economy due to increased load on main pump
- Possible transmission slipping or harsh shifting
03. Step-by-Step Diagnosis
Step 1: Scan for additional codes and record freeze frame data.
Step 2: Visually inspect the auxiliary pump connector and wiring for damage, corrosion, or loose pins.
Step 3: Using a multimeter, measure resistance across phase W and compare to specifications (typically 0.5-2 ohms).
Step 4: Check for voltage at the pump connector with the engine running and A/C on (if applicable).
Step 5: If wiring and voltage are OK, replace the auxiliary transmission fluid pump motor.
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 the auxiliary pump failure can lead to transmission overheating and damage. Short trips to a repair shop may be acceptable if transmission temperature stays normal.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for diagnosis and parts, but labor can add $100-$300 depending on the vehicle. Total repair cost is usually $150-$450.