my service engine soon light was on once before because my syatem was draining and killing my batery that was an easy fix I just replced the battery with an optima yellow top deep cell battery and have not had any problems since.... but now my light is back on and I know it's not my battery again, and all the guages seem to be reading normally, the car shifts fine (a lil hard every now and then) but other than that I don't know what the problem may be, PLEASE HELP ME!!!!!!!

 

From your other posts, I can see that you have a 2000. Please add this information and anything else (like 4wd, auto ,etc) to your signature.

You need to get the code read. Go to your nearest Autozone or Advanced Auto and have them read the codes. Let us know the exact code(s) (Pxxxx - where 'xxxx' is a 4 digit number). We'll be able to help you out a lot better once we know the codes.

 

I finally figured out what was wrong with my service engine soon light.....it came the hard way though, I was off roading at a place called joe battle, very nice it has good steep hills and lots of ruts and plateaus it's beautiful, anyways I ended up taking my stock 2wd blazer and getting stuck in the sand repeated times the 1st time tho was the worst my truck completely died I was very puzzled as to why this happened but then I figured it out.... my battery the terminal was loose not enough to notice just by looking at it but if I were to wiggle it it was a little loose so I just tightened that bad boy up and BAM!!! everything was good as new, no service engine soon light my truck fired right up and I was pulled out by my buddy (he has a trd tacoma) I just though I'd share this experience with everyone just encase you know of anyone that has had or may have a similar problem, thanks for your patience if you read throug this post.

 

Your light may not have been on because of a drain in the battery. Chances are you do have a problem somewhere in the system that needs addressing. When the SES light comes on, that means that the PCM has registered a fault of some kind and the code really needs to be read to determine where that fault is. By having the cable get loose and lose connection, this simply reset the PCM. It will run through all of its checks and balances again and if the problem is still there, you'll see the SES light again. At that time, get the codes read and report back here. We'll try to determine the cause of the problem.

If it doesn't come back, well then good, but that is rarely the case...

 

how long will it take for the light to come back on if it's going to?

 

It depends..there are different types of codes. Most codes are set after one failure, but will not turn on the SES light until the diagnostic test is run and failed on two CONSECUTIVE drive cycles, so it could be a very long time if there is an intermittent condition causing the failed test.