Auxiliary Transmission Fluid Pump Motor Supply Voltage Low
The P0B0A code indicates that the powertrain control module (PCM) has detected a low voltage condition in the supply circuit for the auxiliary transmission fluid pump motor. This pump is typically used in hybrid or start-stop vehicles to maintain transmission fluid pressure when the engine is off. Low voltage can be caused by a weak battery, poor electrical connections, a faulty pump motor, or a wiring issue. If left unaddressed, it may lead to transmission damage or drivability issues.
01. Most Common Causes
- Weak or discharged battery
- Corroded or loose wiring/connectors in the pump circuit
- Faulty auxiliary transmission fluid pump motor
- Blown fuse or relay for the pump circuit
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission shifting delays or harsh shifts
- Transmission fluid leaks
- Reduced fuel economy
03. Step-by-Step Diagnosis
Step 1: Scan for other codes and check freeze frame data.
Step 2: Inspect battery voltage and charging system; ensure battery is fully charged.
Step 3: Visually inspect wiring and connectors for damage, corrosion, or looseness.
Step 4: Test the auxiliary pump motor supply voltage at the connector using a multimeter.
Step 5: Check fuses and relays related to the auxiliary pump circuit.
Step 6: If voltage is low with good battery and wiring, test the pump motor resistance and replace if out of spec.
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 low voltage can cause the pump to fail, leading to transmission damage. Short trips to a repair shop are acceptable.
How much does it cost to fix?▼
Costs range from $150 to $400 depending on the cause. A simple wiring repair may be under $200, while replacing the pump motor can be $300-$400.