Auxiliary Transmission Fluid Pump Motor Phase V Current High
The P0B05 code indicates that the Powertrain Control Module (PCM) has detected an excessive current draw in phase V of the auxiliary transmission fluid pump motor. This pump is responsible for circulating transmission fluid to cool and lubricate the transmission when the engine is off, such as during start-stop events. High current typically points to a short circuit, a failing motor, or a wiring issue. If left unaddressed, it can lead to transmission overheating, reduced pump performance, and potential transmission damage.
1. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission overheating or slipping
- Reduced fuel economy due to start-stop system deactivation
- Unusual noises from the transmission area
2. Most Common Causes
- Auxiliary transmission fluid pump motor shorted or damaged
- Short to voltage in the pump motor phase V wiring
- Faulty transmission control module (TCM) or power module
- Corroded or poor electrical connections in the pump motor harness
- Damaged auxiliary pump relay or power controller
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 loose pins.
Step 3: Measure resistance and current draw of the pump motor phases using a multimeter and compare to specifications.
Step 4: If wiring and connections are good, replace the auxiliary transmission fluid pump motor.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended. High current can damage the pump or wiring, and the pump may fail, leading to transmission overheating and potential damage.
How much does it cost to fix?▼
Repair costs typically range from $150 to $400, including parts and labor. The auxiliary pump itself costs $100-$250, and labor adds $50-$150.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.