💨 EVAP System Analysis

The Evaporative Emission Control (EVAP) system is designed to prevent fuel vapors from escaping into the atmosphere by capturing and storing them in the charcoal canister. Understanding the operation of the EVAP system can help diagnose issues that may affect your vehicle’s performance and emissions.

System Sealed

A properly functioning EVAP system should be sealed, maintaining a vacuum below -2.0 inHg. During the test, the system should hold this pressure stable. If no issues are present, there will be no P0440 or P0442 codes, and the purge valve will cycle normally.

Small Leak

A small leak is indicated by a pressure loss between 0.020" and 0.040". This may trigger a P0442 code. If you encounter this, the first thing to check is the gas cap, as it may not be tightly sealed. Also, inspect line connections for any signs of leaks or wear.

Large Leak

If the system cannot hold vacuum and you see P0440 or P0455 codes, it indicates a large leak in the system. In this case, it’s important to check for damaged lines, as well as inspect the canister and valves for faults or damage that could cause the leak. Addressing large leaks promptly helps maintain fuel efficiency and ensures the system operates as intended.