P0442 - Evaporative Emission System Leak Detected (Small Leak)

The OBD-II code P0442 indicates that the engine control module (ECM) has detected a "Small Leak" in the Evaporative Emission Control (EVAP) system. The EVAP system is designed to capture and store fuel vapors from the fuel tank, preventing them from escaping into the atmosphere. A small leak in this system means that fuel vapors are not properly contained, leading to increased emissions.

Possible causes of the P0442 code include:

1. Loose or damaged gas cap: Just like in the case of P0455, a loose, damaged, or missing gas cap is a common cause of this code. Make sure the gas cap is tightly secured and in good condition.

2. Faulty EVAP system hoses: Similar to P0455, inspect the EVAP system hoses and connections for any signs of damage, disconnection, or deterioration. Even a small crack or loose connection can trigger the code.

3. Faulty EVAP system purge valve: The purge valve controls the flow of fuel vapors from the charcoal canister to the engine. If it's stuck open or closed, it can cause a small leak in the EVAP system.

4. Cracked or damaged charcoal canister: The charcoal canister absorbs and stores fuel vapors. If it becomes damaged or cracked, it can lead to a small leak.

5. Faulty fuel tank pressure sensor: The fuel tank pressure sensor monitors the pressure inside the fuel tank. If it's malfunctioning, it may not accurately detect leaks or changes in pressure.

6. EVAP system leak detection pump malfunction: The leak detection pump is responsible for testing the EVAP system for leaks. If it fails to function correctly, it can't accurately detect small leaks.

To diagnose and resolve the P0442 code, you can follow these steps:

1. Check the gas cap: Verify that the gas cap is tightly secured and in good condition. If it's damaged or missing, replace it with a new one.

2. Inspect EVAP system hoses: Examine the EVAP system hoses and connections for signs of damage, disconnection, or deterioration. Address any issues found during the inspection.

3. Check the EVAP system purge valve: Test the purge valve's functionality and replace it if necessary.

4. Inspect the charcoal canister: Check the charcoal canister for any cracks or damage. Replace it if it's compromised.

5. Test the fuel tank pressure sensor: Use a diagnostic tool to check the fuel tank pressure sensor's readings and functionality. Replace the sensor if needed.

6. Check the EVAP system leak detection pump: Test the leak detection pump to ensure it's working properly. Replace it if it's faulty.

7. Reset the ECM: After making any necessary repairs or replacements, reset the ECM using a scan tool.

If the issue persists after these steps, it's recommended to have the vehicle inspected by a qualified mechanic or dealership. They will have the necessary tools and expertise to perform advanced diagnostics and identify the specific cause of the small EVAP system leak and recommend the appropriate repairs.