Auxiliary Transmission Fluid Pump Hydraulic Leakage
The P0B0C code indicates that the transmission control module (TCM) has detected a hydraulic leakage in the auxiliary transmission fluid pump circuit. This pump is typically used in hybrid or start-stop vehicles to maintain transmission fluid pressure when the engine is off. A leak can cause insufficient fluid pressure, leading to transmission slippage, harsh shifting, or failure to engage gears. The issue may stem from a faulty pump, damaged seals, or low fluid level.
01. Most Common Causes
- Faulty auxiliary transmission fluid pump
- Damaged or worn pump seals or gaskets
- Low transmission fluid level or contamination
- Electrical issues (wiring, connectors, or TCM)
02. Symptoms You Will Notice
- Transmission slipping or delayed engagement
- Harsh or erratic shifting
- Check Engine Light illuminated
- Reduced fuel economy or performance
03. Step-by-Step Diagnosis
Step 1: Scan for codes and verify P0B0C is present.
Step 2: Check transmission fluid level and condition; top off or replace if necessary.
Step 3: Inspect auxiliary pump and its seals for visible leaks or damage.
Step 4: Test pump electrical circuit (voltage, ground, resistance) using a multimeter.
Step 5: If pump and wiring are OK, perform a hydraulic pressure test to confirm leakage.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended. Driving with a hydraulic leak can cause transmission damage due to insufficient lubrication and pressure. Have the vehicle inspected as soon as possible.
How much does it cost to fix?▼
Repair costs typically range from $150 to $400, depending on the cause. Replacing the auxiliary pump can cost $200-$350, while seal repairs or fluid changes are less expensive.