Gas cap problem??

I have a check service engine soon idiot light coming on my 2000 sl1 single
cam. I thought it might be time to invest in a obd-ii code reader but I did
have a co-worker suggest that the frequency of my light coming might be a
gas cap problem. The light comes on and stays on when I start the car but
every 4th or 5th start the light goes out ONLY to come on aging for the next
4 stops and thus the process is repeated.

He used to have a 97 tarus with the same problem and a new gas cap solved.

Any suggestions if a 97 tarus emissions system give the same idiot light
sequecences as a sl1? (both are obd-ii)

 

It's pretty much impossible to predict what the code may be by when/how
often the light is on. If the gas cap is obviously damaged/leaking that's a
place to start, but I'd say the chances of a new one fixing the problem are
low..

 

I have a defective gas cap( it will not stay on), and so far no lights
are coming on! I am in the process of getting a locking gas cap now, but
I do not understand why no trouble lights, even when the cap is
completely off? Could a bad gas cap effect gas mileage? My gas mileage
is really not very good. Thanks!

 

What model year is this? Only 1996 and later will detect evaporative
leakage. Also, it only runs the test under certain conditions, so if it
hasn't been broken very long it may not have detected it yet.

 

Well I bought a new Locking Gas Cap for my L300 this weekend at my
Saturn dealer. $33 for it, and it works a lot better then the original
gas cap. At least you can tell it is on, after you tighten it down. And
now I have a little peace of mind knowing that my Gas Tank is locked. I
do not know if this will help my gas mileage any, but I am hoping it
will.