engine check light??

I have a '00 Jetta GLS. The engine check light came on abouta month ago. Diagnosed with the dealer..they told me to replace the oxygen sensors and after about 300bucks it was cleared.

Only 2 weeks after, the light came on again...after a day or two it went off and it came back on again ...and it is still on..
What can i do before taking this to the dealer again??
They charge me $85 just to run the computer diagnosis. I live in canada. so i dont know whether we have autozone here (where i heard you can check this for free)

I've read some posts here - saying to disconn the negative battery cable. Does this mean just unplug the battery cable for about 10min and reconnect it? what does this do exactly?

Thanks

On a 2000 model it won't really help anything (& can actually cause problems). You need to find out what code you are getting & go from there.

any way of getting this code setting witout having to pay about 100bucks?? (i'm in canada)

Yea, buy a $60 code reader/eraser from ebay.

You should have some larger auto parts chains that keep scanners they will loan to customers....

any way of getting this code setting witout having to pay about 100bucks?? (i'm in canada)
I have had my light come on and off due to not putting the gas cap on tight enough. Always make sure it clicks. I did not do it and went to autozone for the free reading which said secondary air intake. Whatever that ment. It turned out to be the gas cap. The light would come on and off occaisonally with the car running normal.

my ck eng lt came on 2 years ago.Took car to dealer and after 2500 US dollars the car runs great but the ck eng lt never went out.it comes and goes.Then I discovered if I bought gas at a particular gas station it goes out and stays out.So....I get gas at only one station....if I use any other gas the light comes on.VW dealer never could give me an explanation.It was always some other problem that they wanted to fix.When I get the money I will have the catalytic converter looked at but until then~~~~~~

Many people automatically assume a check engine light means bad cat converter or bad 02 sensors...when in reality hundreds of things can cause a CEL. It is unfortunant that your dealership cannot pinpoint the problem...but prior to simply spending more money on random parts that may or maynot need replacing...I'd suggest trying a different mechanic. Also about the cat specifically, it probably doens't need to be replaced unless you notice a smell like rotten eggs, and/or you are getting random backfires.