I recently have done a full tune up on my car including changing the gaskets to fix my vacuum leak and replacing the fuel filter. I now have no more check engine light, but after driving the car a few hundred miles, I noticed that my comp and evap monitors are still "not ready". I am not really worried about the comp monitor right now, but the evap monitor has always cleared fairly quickly to "ready" after a reset.

I wonder if replacing my original gas cap has any relation to this problem. Whenever I used to fill up my gas, I would hear a hiss sound when removing the original cap. Now with my new gas cap, I NEVER hear the hiss sound. I made the mistake of throwing away the original cap, so I wouldn't know if that makes a difference or not. Could this mean my fuel pressure is low or what could be the issue?

I have tried the Evap driving cycle... don't think it worked.

 

Hope it's that. Somewhere there's a complicated file about what (fault) suppresses what (monitors, faults, etc) that you really don't want to struggle with.

 

So I bought the original Jaguar OEM gas cap instead of using the aftermarket cap from the local auto parts store and now my evap monitor is finally set to "ready".

 

Hooray!