Olds 2004 with service engine soon on



My 2004 Olds has the service engine soon light on. I checked and it shows P0455 code, with two large leaks indicated.

I chnage the gas gap with an original new one and reset but the problem is not solve. There is no other problems or symptoms, except for the emmision inspection required by MD.

On the internet, some posts that it is EVAP problem. Could you helpe me detect where to look exactly and what shall I tell mt repair shop to do exactly.




P0455 - Evaporative Emission Control System Leak Detected (gross leak).

Last time I faced this code, the leak was a very obvious hose disconnected on the evap canister. For a large leak, there must be something broke or disconnected. You’ll need to look under the car, especially at the evap canister at the back of the car near the gas tank and all the hoses and lines associated with the gas tank and evap canister. A gas cap with a leaking seal or simple cracked hoses would give a small leak problem.


If you can’t see any obvious leaks, you may want to have a shop do a " smoke test "where smoke is pressurized into the gas tank and they see where it comes out.