Auxiliary Transmission Fluid Pump Motor Supply Voltage Circuit High
The P0B0B code indicates that the powertrain control module (PCM) has detected a voltage level in the auxiliary transmission fluid pump motor supply circuit that is higher than the specified range. This pump is typically used in hybrid or electric vehicles to circulate transmission fluid when the main engine is off. A high voltage condition can be caused by a faulty pump motor, a short to voltage in the wiring, or a malfunctioning PCM. This issue can lead to inadequate transmission fluid circulation, potentially causing transmission overheating or damage.
01. Most Common Causes
- Faulty auxiliary transmission fluid pump motor
- Short to voltage in the pump motor circuit wiring or connector
- Corroded or damaged wiring harness
- Malfunctioning PCM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission overheating or slipping
- Reduced fuel economy in hybrid vehicles
- Transmission fluid leaks near the pump
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to retrieve all stored codes and freeze frame data.
Step 2: Visually inspect the auxiliary transmission fluid pump and its wiring for damage, corrosion, or loose connections.
Step 3: Using a multimeter, check the voltage at the pump motor connector with the ignition on. Compare to manufacturer specifications.
Step 4: If voltage is high, disconnect the pump and check for a short to voltage in the circuit. Repair as needed.
Step 5: If the circuit is okay, test the pump motor resistance and replace if out of spec.
Step 6: Clear codes and test drive to verify repair.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive with this code, as it can cause transmission overheating and damage. Have the vehicle inspected as soon as possible.
How much does it cost to fix?▼
The cost typically ranges from $150 to $400, including parts and labor. The pump itself can cost $100-$250, and labor adds $50-$150.