P0455 fault code means dealing with your evaporative system which is designed to avoid leakage of fuel gas vapor to the atmosphere. However, this code expands this leakage problem further by having a purge solenoid valve which allows the flow of gas vapor between the fuel tank, fuel canister and throttle body. This valve solenoid is usually controlled by the engine computer after getting all the signals from the engine input sensors. When the electric solenoid is defective, the flow could be disrupted and prevent the circulation of gas vapors in the vacuum system. Furthermore, the most common problem here is a vacuum leakage which can occur at the solenoid, canister, vacuum hoses and especially coming from a loose gas tank cap. Such leakage will allow hydro carbon gas like your fuel gas vapor to escape to the atmosphere.
During P0455 fault code, any leakage in the gas flow from the tank will be detected by the computer since it monitors the combustion parameters by getting the fuel mixture signal from the oxygen sensor. When this happens, this code will be flashed in the vehicle dash panel. To correct, always go to the gas cap first and make sure it has good sealing gasket and installed tight. Next, visually inspect for vacuum leakage by checking for ruptured vacuum hoses, plug pcv valves or cracked evaporative canister housing.
When P0455 fault code is present, any vacuum leakage can be seen by signs of wetness in the canister cylinder area. If a vacuum hose connection is leaking, the defective area should be wet with gas or even a smell of gas. Once this vacuum test is exhausted and dried, the best way to find the leak is to have it checked by a smoke machine used by garages to detect miniature gas leak not visible to the human eye.
On some gm vehicles, this P0455 fault code can be traced to a loose vacuum hose located on top of the fuel tank. You can easily see it when you drop the tank. If you don’t have a smoke machine machine available near you, you can pressurize the vacuum hoses up to 10-15 psi to find the leak. You might have to use a vacuum diagram so you can pinch any vacuum line while applying the appropriate air pressure. Fixing this P0455 fault code is always possible if you provide the complete symptoms for your engine.