The EVAP system prevents fuel vapors from escaping into the atmosphere. The P0443 code means the onboard diagnostic (OBD-II) system has detected a leak that's larger than what it considers acceptable.
The leak could be caused by several things, including:
* Loose or damaged gas cap: This is the most common cause. A simple fix often involves replacing the gas cap.
* Leaking fuel tank: A crack or hole in the fuel tank itself.
* Loose or damaged EVAP hoses: The hoses that connect various parts of the EVAP system can become cracked, deteriorated, or disconnected.
* Faulty EVAP purge valve: This valve controls the flow of fuel vapors.
* Faulty canister vent valve: This valve regulates pressure in the charcoal canister.
* Problems with the charcoal canister: The canister itself may be damaged or clogged.
Troubleshooting steps often involve:
1. Checking and tightening the gas cap: This is the first and easiest thing to do.
2. Visual inspection of all EVAP system components: Look for any obvious cracks, damage, or loose connections to hoses and other parts.
3. Pressure testing the EVAP system: A mechanic will use specialized equipment to pressurize the system and detect leaks.
4. Using a scan tool to retrieve more data: This can help pinpoint the specific area of the leak.
It's recommended to take your Ford Expedition to a qualified mechanic for proper diagnosis and repair. Simply replacing parts without proper diagnosis could lead to unnecessary expenses.
