Auxiliary Transmission Fluid Pump Motor Phase W Current High
The P0B08 code indicates that the Powertrain Control Module (PCM) has detected an excessive current draw 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 stop-start events or when the engine is off. High current can result from a short circuit, a failing motor, or a faulty pump assembly, potentially leading to transmission overheating or damage.
1. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission overheating or slipping
- Reduced fuel economy due to pump inefficiency
- Unusual noises from transmission area
2. Most Common Causes
- Short circuit in phase W wiring or connector
- Failing auxiliary transmission fluid pump motor
- Faulty pump assembly causing excessive drag
- Corroded or damaged electrical connections
3. Step-by-Step Diagnosis
Step 1: Scan for additional codes and record freeze frame data.
Step 2: Visually inspect the auxiliary pump wiring and connector for damage, corrosion, or shorts.
Step 3: Measure resistance and current draw on phase W using a multimeter; compare to manufacturer specs.
Step 4: Test the pump motor by applying direct power and ground; check for smooth operation.
Step 5: If wiring and motor test OK, replace the auxiliary transmission fluid pump assembly.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended. High current can damage the pump or PCM, and reduced fluid circulation may cause transmission overheating and failure.
How much does it cost to fix?▼
Diagnosis typically costs $50-$150. Replacing the pump assembly can range from $200-$600 including parts and labor.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.