Auxiliary Transmission Fluid Pump Motor Phase V Current High
The P0B05 code indicates that the powertrain control module (PCM) has detected excessive current draw on phase V of the auxiliary transmission fluid pump motor. This pump is responsible for circulating transmission fluid when the engine is off, such as during start-stop events or electric-only operation in hybrid vehicles. High current typically points to a short circuit, a failing motor, or a wiring issue, which can lead to pump failure and potential transmission damage.
01. Most Common Causes
- Short circuit in the pump motor windings
- Faulty auxiliary transmission fluid pump motor
- Damaged wiring or connectors in the pump circuit
- Failed pump control module or relay
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission overheating or slipping
- Reduced fuel economy due to pump not operating
- Possible transmission warning messages on dashboard
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to retrieve all codes and freeze frame data.
Step 2: Visually inspect the auxiliary pump wiring and connectors for damage, corrosion, or loose connections.
Step 3: Measure resistance and current draw on phase V of the pump motor using a multimeter; compare to manufacturer specifications.
Step 4: If wiring is intact, test the pump motor by applying direct power and ground; if current is high, replace the pump.
Step 5: Check the pump control module and relay for proper operation; replace if faulty.
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. Have the vehicle inspected promptly.
How much does it cost to fix?▼
Repair costs typically range from $200 to $600, including parts and labor. The auxiliary pump itself costs $100-$300, plus diagnostic and labor fees.