91 Honda Acord) Flashing Green (S) an Check engine

The flashing green key icon when turning off your car? Ignition security system, requires chipped key to start. It's sort of like the GM and Ford flashing red light to announce the security system is active.

you may need to have your immobilizer reset at the honda dealership.

try another key it sounds like the imoblizer

the flashing S light on your car is your tcu "transmission control unit" sending a trouble code to your dash this could mean alot of differant things if im not mistaken it will be an electrical problem not mechanical. is your speedometer just randomly jumping? the reason i ask is i drive a 91 as well and my S light is blinking and my speedometer jumps and sometimes doesnt work at all the the code for the S or tcu is 4 which is the vss "vehicle speed censor" eventually your check engine light will probably come on and if the code is 17 then its your vss as well but you can check the code by getting either a paper clip or small wire and using it as a jumper wire there is a little blue wiring harness on the passenger side of your car under the glove box use the paper clip or wire and plug them in "dont worry you wont get shocked ive done this plenty of times and in the rapair manual it tells you to do this" when you do this make sure the paper clip or wire is secure and put you key in the ignition and turn it to where your dash lights up but dont start the car the S light will start to blink count the blinks "1 long blink is 10, 1 small blink is 1" example if the light stays on for a couple of seconds and turns off and then blinks 4 times that would be code 14, if your check engine light blinks count that as well if you need help with checking any of it there is a video on you tube i believe the title is how do you check the check engine light on a 91 honda accord. or something of that nature. if you get the codes tell me what they are I may be able to find them and get more specific about what is goin on I hope this helps

You have a bad speed sensor on the tranny. Click here for the fix.

Either your battery is weak or short circuited. check the wires manually if any is extra hot.

is it SPORTS MODE try and press any button located near the shifting assembly

If the green light is one of your turn signal arrows. it means you have a burnt bulb.

check under seat and see if wire connector has come loose what green light are you talking about if you mean the green "s" light you just hit the switch on the shifter for firmer and higher shifts if its an automatic transmission.

The s light might mean a problem with the transmission computer it is right next to the computer for the car under the carpet. does the car shift gears? if it don't the tcu is burned out ,it is a common problem for 91-93 accords