1991 Honda accord auto tranny, shifting and

Your AT Control Unit is fried. There is one capacitor, and one resistor that fries on all of these faulty, defective little boxes. If you were to remove the box, which is under the passenger side carpet, and look at the chip board inside, you would probably see a little 33uf 35volt capacitor with black burnt gunk all around it.

Certain VIN numbered Hondas recieved these ATCUs from a factory in Georgia, which was responsible for the faulty capacitors. I replaced mine yesterday with a $20 junkyard variety. When I looked inside of it, the chip board was a different color, indicating it was made in a different factory. If the chip board in yours is green, it's probably of the Georgia variety. My new one had an odd-looking orange chip-board, with no blown up looking components.

After installing the new Unit, I now have all gears and no stupid blinking obnoxious (S)-light, whereas before, I had the same problem you're having. It works wonderfully now. Good luck finding one though, because I saw about ten cars there that had already had this box stripped out, which tells me that this is a very common problem among these cars. A brand new one is $187 from Honda, and a reconditioned one is $120.

At another site similar to FIXYA.com, I read of a guy that sent his box to radioshack, and they tested and replaced the faulty parts. This would still cost less than getting a new one, but you would have to wait for them to fix it. I plan on doing this to my old one, so I'll have a backup if this new one eventually does the same thing. I may fix it myself with a soldering iron, if I can find the right resistor. The capacitor though, is an easy find. Good luck if you decide to try this. I have a feeling that you would feel very satisfied if you were to replace two tiny little parts and fix the whole car.

I also suggest that you search the web, especially FIXYA.com, for other people having the same, or similar problems. You will find that you are not alone in your struggle to drive a fully operational, properly functioning Honda Accord. Mine has 257,000. I hope yours makes it that far plus another 100k or more. God Bless You, and good luck.