2000 SL1 P0442 code
 

So far I have replaced the thermostat, engine coolant temperature sensor, gas cap, and fuel tank pressure sensor. After filling the gas tank up after each item replaced and clearing the code, my SES light came back on after driving back and forth to work after about 123 miles in 5th gear slowing down for a 4 way stop sign between 25 and 30 mph...4 times in that very same spot!!! Filling the tank up on a Monday morning the light came on every Wed evening when leaving work, exact same location, slowing down for that 4 way stop sign. Tech 2 scan tool freeze frame says 190 degree coolant temperature and fuel tank pressure sensor 0.00 volts. Has anyone solved this P0442 mystery? I also sprayed about 1/2 can of carb cleaner around the mating surface of the intake manifold to the cyl head and no change in rpm. Thanks in advance.

Could be a couple of things, but the first thing I'd do, is to look carefully at the fuel filler neck and flange where the gas cap goes. The system is telling you that you are loosing vapor containment which usually points to an improperly tightened gas cap, or a defective one. Since you've already replaced the cap, I guess we can ignore the "defective gas cap" comment.

The fuel vapors are normally routed by vacuum hoses to the charcoal canister for storage, then routed to the engine via the purge control valve drawing the vapors in the canister into the intake manifold. Perhaps, the hoses have a small crack/split in them, allowing the vacuum to bleed off, thereby setting the SES light

2000 sl1 p0442
 

Thank you this weekend I will check all hoses, etc. There is a few very small nicks/dings on the top of the filler neck where the cap contacts. Also I purchased a cap at Advance Auto Parts, maybe I will purchase one from a local Saturn service center still open. These nicks/dings are very very small, but you can feel them with your fingernail. I read a post where someone put a rag inside the neck and sanded the neck smooth, applied a little grease and the problem went away. I did try some grease after replacing the cap but the light still came back on. I did not want to sand down the neck thinking that it would lower the mating surface and make it worse. Underneath the drivers door there is a test port with a green cap, I was thinking of putting a small amount of air into that line and listening for leaks, or would that put gas into the cannister? Maybe do it when the tank is almost empty, any thoughts on that?