S Light But different then all the others - Need help

I own a 1990 honda accord lx in great shape mint inside decent out.Runs tip top and all stock a one owner car and great working until today.

I noticed after work today for the first time the s light came on when I started my car after it had sat on a jobsite all day.Mind you on the way to work and never before this light had never come on because I had never used the sport mode just figured no use I knew what it did and wasnt interested so never used it.

But this wasnt the only problem that happened with the s light when the s light would come on it would actually shift to sport mode by itself and I wasnt doing this lol.So the first time it actually went off and came back on I had just gotten on the highway hit about 60 and bamn the s light comes on shifts to sport mode and basically tacks out from the downshift but of course could still handle 55 or so.No damage was done there but still as I got off the highway and made my way home it began to do this more often and more often shifting to sport mode by itself.

Very strange it was and when I actually got to my house and put it in park I realized I could here a little clicking noise in my auto shifter coming from in side it ,it seemed like anyway.It would make it as the light would come on and off.I couldnt here that as I was driving due to the small amount of noise it makes while driving it was a quiet clicking.

Anyway that is basically the only thing Ive ever had go wrong with it and its been great to me.Would love to hear your opinions on it and how much it would be to fix it as to not get ripped off on this mission.Thanks for all your help ahead of time.

I used the search feature and read many blinking s light posts but not one of them I read said there car was actually shifting while doing this ,they were just saying it would blink.My car will blink but when it does it actual goes to sport mode which obviously I dont want it to do.Seems electrical or something but im not much of a mechanic thats why im asking to get a good responce and a price so I know what im dealing with here thanks alot again.

I would lean towards the TCU or TCM, tranny control unit/module. You are probably losing 4th gear, which you are interpreting as it going into sport mode. This is actually a kind of 'safety' mode to indicate that there is a problem with the TCU.

If you do a search for TCU or TCM, you can find quite a bit of info, but basically it is a little electronic box under the kickboard of the passenger seat (where the passenger's feet would be up near the dash) You pull back the carpet, and behind that metal shield there are 2 computer boxes...I forget which is the TCU (I want to say the one on the left, but double check that before you take my word on it). Anyway, the dealership will charge huge amounts of money for a new one. So go to your local junkyard or ask around on here. Tyically you can find a used one for $50 or less. It takes 15 minutes for the average person to swap.

Thanks a million man you saved me 600 on the part and how ever much on the labor.I did it in about a half an hours time and got the part from a local salvage yard for 75 bucks with a 30 day warrantee.The 2 plastic wire clips were hardest to get at out of it all taking the 4 bolts off was cake but getting to those clips was no joke lol.

Cant beat the help saved me a pile and my car is now shifting smoother then it ever has very happy with the help here thanks a ton again man really helped me out.

P.S. It was the box on right as your looking at it from sitting in the passenger seat.

Thanks again appreciated greatly.

No problem, glad it worked out.