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 used in hybrid and electric vehicles to circulate transmission fluid when the main engine is off, ensuring proper lubrication and cooling. 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 transmission overheating or damage if not addressed.
1. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission overheating or slipping
- Reduced fuel economy in hybrid mode
- Transmission fluid leaks near the pump
2. 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)
3. 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: Test the pump motor supply voltage at the connector using a multimeter; compare to manufacturer specifications.
Step 4: Check for shorts to voltage by testing continuity between the supply circuit and battery positive.
Step 5: If wiring is intact, test the pump motor resistance and operation; replace if out of spec.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive with this code, as the auxiliary pump may fail, leading to transmission damage from lack of lubrication and cooling.
How much does it cost to fix?▼
Repair costs typically range from $150 to $400, including parts and labor, depending on the cause and vehicle model.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.