Auxiliary Transmission Fluid Pump Motor Phase W Current Fault
The P0B06 code indicates a malfunction in the auxiliary transmission fluid pump motor's phase W current circuit. This pump is responsible for circulating transmission fluid when the engine is off (e.g., during start-stop events) to maintain lubrication and cooling. The diagnostic trouble code (DTC) is set when the powertrain control module (PCM) detects an abnormal current draw or open circuit in phase W of the pump motor. This can lead to inadequate fluid circulation, potentially causing transmission overheating or damage.
1. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission slipping or harsh shifting
- Transmission overheating
- Reduced fuel economy due to increased load on engine
2. Most Common Causes
- Faulty auxiliary transmission fluid pump motor
- Open or short circuit in phase W wiring or connector
- Damaged pump motor control module
- Low transmission fluid level or contamination
3. Step-by-Step Diagnosis
Step 1: Scan for additional transmission-related codes and freeze frame data.
Step 2: Inspect the auxiliary pump connector and wiring for damage, corrosion, or loose connections.
Step 3: Measure resistance of pump motor phases; compare to specifications (typically 0.5-2 ohms).
Step 4: Test pump motor operation by applying battery voltage directly (if safe) or using a scan tool to command the pump on.
Step 5: Check transmission fluid level and condition; top off or replace if necessary.
4. 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, especially in stop-and-go traffic or start-stop conditions.
How much does it cost to fix?▼
Repair costs typically range from $200 to $600, depending on whether the pump motor, wiring, or control module needs replacement, and labor rates.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.