service engine light

this one has got me quite confused at the moment. my service engine soon light comes on about everytime i drive my car. but it doesnt come on right away. i have noticed that it seems to come on while im coasting before i brake to come to a stop. i had it checked on the diagnostic and no codes came up. so im lost. any ideas out there?

It might be a faulty light. Also, when the light comes on it is usually something to do with the emissions system (thats what it says in the manual). Check the emission hoses and stuff. Good luck.

what year is it
its probably just the egr valve or something in the emissions like xlwhellraiser said

its a 94. i figured it had something to do with the emission system, i just didnt know what. guess ill give it all a good run down.

I have an 89 that was giving me codes just in the morning when I went to work. In the afternoon it was fine. At first it was an MAF code,so I tightened up around the plenum and it started giving me a o2 code ,so I put in an O2 sensor,and it was still there. So I changed the computer and haven't had one since. That was a year ago. The difference is I did get some codes ,but it could be a similar problem. Good luck, Tom

I think in '94 on GM cars, you can still use the old way of getting the codes out of the computer. Hopefully it is still old enough to do this, if not then you won't see anything happen. Take a large paper clip, unfold it, stick both ends of the paper clip in the the car's computer plug, the plug should be under the driver side dash, just beneath the steering wheel column on the right side. The plug will look like a long computer plug in. Take the paper clip ( with the key on... not the engine on ) place one of the ends of the paper clip into the far left insert and the other on the far right, make sure they have good connection, it sucks to hold it there but it pays off. What you will see if you have done it properly is a code will flash on your check engine screen. Count how many times you see to check engine or service engine light flash. The first 2 flashes are standard, don't count them, it will flash like this if you have a code 43.... flash, flash,...... long wait..... flash,flash,flash,flash,.....wait.. flash,flash,flash.......long wait..... flash, flash. Remember there are 2 standard flashes before and after the code is shown. There is always a wait in between the standard flash and the problem code. The process will repeat it once.. if you see it go for a thrid time, then you have another code you need to find out what it is. After you get the code, look up the code on the net, or call your local mechanic, and ask them what that code is.