Check Engine light on the Monte Carlo

[96BlackRoseZ26]

Well it seems I have the new car curse.  The same thing happened to me when I bought the Z26 5+ years ago.  The check engine light came on for me a couple weeks after I bought it.  The one on the Beretta took me almost a year to figure out and get it to stay away, but I don't want this to go on that long, especially since it is such a harmless sounding problem.

I had Autozone pull the code the first time since I had nothing that would do it for me.  It came up as a P0440 and he said that it is almost always a loose or bad gas cap.  I have since gotten a set of ELM based OBDII readers off of ebay that will allow me to hook up my laptop to the car to pull codes and clear a check engine light.  The light has come back twice since being cleared the first time, each with the P0440 code being set.

How often is a code P0440 really just a loose/defective gas cap?  I'm using DigiMoto on the laptop to check the codes and clear them, but is there something I can use on the car, short of getting a GM Tech II (I had access to one with the Beretta's P0441 code and made it much simpler to diagnose) that will allow me to cycle the Evap system components to verify it's operation so I can troubleshoot it properly without throwing pieces parts at the car?  I would really prefer it be laptop based, and super-cheap/free would be a bonus, especially with the new house payment, and new car payment.

I know it's not Beretta related, but I know there are some people out there in the Chevrolet fix-it field that might be able to offer some advice.  I would greatly appreciate and welcome any and all replies.

Thanks in advance.

[93gt--z]

Although it is often caused by the gas cap, if it comes back that much, my money is going on the purge unit..I believe it would be a retangular box up under the drivers side rear bumper. Kinda tricky spot to get at, but that unit could be the colpret. Not sure what program you can run, my best offer would be just get the tech II on it cause I know you can cycle the valve on and off with that for sure.

[chevythunder]

Take it to the dealer if its new. If not find a shop that has a smoke machine and find where the EVAP leak is then you don't have to just throw parts at it.