1996 cavalier P0440 + cooling fan always runs

Ok here's exactly what happened - this may not all be related, but its a true full account of what happened. I failed the enhanced smog test for LA county, decided to put some STP fuel system cleaner in a full tank, and one morning this week (before the tank was empty) I was driving to UCLA and all of a sudden the cooling fan kicks on and the MIL light turns on. Keep in mind I still haven't retaken the smog test - I wanted to get a scan tool and see what the heck was up with my cavalier. Now, every time I start the car the MIL light is on and the cooling fan is running - can't turn it off. This happened before, I took it to a mechanic and he fixed the problem - he mentioned he found a leak somewhere and fixed it. Obviously he didnt really fix it. A scan with an actron cp9135 revealed a single DTC: P0440 = Evap Emission Control System Malfunction. I've been poking around on this forum and found several hits on P0440, but none seem to be exactly my problem. I have done absolutely nothing yet to fix this, so any advice would be appreciated. I'll post what I've done when I do it.

with the cooling fan running check the relay to it

Bpp,
I don't think the 440 has anything to do with it.Your problem is caused by .
1)The CPU temp sensor(making the CPU think the engine is hot).
2)Bad relay (contacts stuck in closed position)
3)Bad CPU (sinking the ground to the relay when it shouldn't)
Disclaimer ,I haven't worked on your year but thats how an 88 Cav was that I worked on
As far as the 440 I'd clear it make sure you put your fuel cap on tight and see if it somes back
Unbe

Ok I cleared P0440 with my scan tool and once I did the MIL disappeared and the cooling fan stopped running. So, it seems every time the check engine light comes on the cooling fan starts running. I can live with that. I'm working on the P0440 problem now, because even though I am able to erase the DTC it comes back after 5 minutes...which indicates the problem is for real.

So I'm experiencing a vacuum leak somewhere...I get that. I'm going to ask the mechanic who worked on this problem last time what he did. I haven't replaced the gas cap, o-ring, or anything else to my knowledge. I checked the PCV today - it was fine, and did show that a vacuum exists at least in that part of the Evap Emission Control System. I didn't disconnect the Evap Control Canister, but a visual inspection didn't show any damage. What I'm wondering now is, if the PCV shows vacuum, can I rule out certain problems like a leaky gas cap and/or the evap control canister? Is the problem that there isn't enough vacuum? I can't tell...