CEL code P0440

I have had this light on constant for almost 3 months now. Before, it used to come on and go off. So I had the code checked and it was P0440. They mechanic said get a new gas cap. So I did and it went off but came back on shortly after. Ever since then it has not went out. I talked to my mechanic and he said there is a leak somewhere. Is this code for a leak or is there something wrong with one of the valves. I was told maybe the purge valve next to the throttle body could be bad. How would I check that? Well any other suggestions on the P0440 light woud appreciated. Thanks in advance.

Any leak in th evap system can set that code, a smoke machine is the most accurate way to pinpoint the problem other than a visual of all involved hoses, lines and fittings.

I agree with Max. This is one of those things where you need a professional piece of equipment (the smoke machine) to pin point the leak. It could be in any of the tubes from the engine compartment all the way to the tank. I doubt the evap purge valve would trip a P0440.

yeah i guess ill have to do that then. how much do you think it would cost to have that smoke test done? thanks.

Varies by region and shop, figure 1 hour labor.