ok.. i have a 1991 honda accord auto tranz. it developed the flashing S light problum a few months back. so i did some reserch found alot out. but thus far have not been able to correct the problum it has multiple symptoms. the S light will flash and the car goes into safe mode leaveing me with only 1st gear and 3rd gear.. it does not always do this sometimes ill start it up and its fine drives normal no flashing light. some tuimes it will start flashing after a few min of driveing. when the S light is flashing the motor idles realy ruff sounds like it has a miss or is out of time. if i put the key in and turn it to on position with out starting it ill hear a loud click comeing from the passinger floor bord where the ecu and tcu are located this only happends when the S light flashe's.. developed a new symptom today car was driving fine no flashing light had all gears traveiling at around 40mph the car infront of me desided to stop suddenly and turn i hit the brake much harder than i ever have in the car but never came to a full stop cause the other car turned out of the way when i accelirated agin the car seemed to be stuck in 1st gear but then finaly sifted into second and then 3rd but the speed and rpm it was shifting at where way higher than it should of been as if i was in a manul and almost tacking the motor out befor shifting.. the S light never flashed when it did this. after resherch this is what i have done so far .. jumpered the blue wires and got code 7 shift silinods.. replaced the shift silinods. discovered that there is no tranz filter and flued needs changed every 30,000 miles .. no clue when it had last been done drained the flued looked realy bad was almost black like oil had some thick sludge in it as well no metal shaveings at all thou was relived there.. filled tranz drove for 800 miles draned and refilled agin. looked much better this time but could tell there was still some sludge mixed in that did not come out the first drain. found out about the TCU capasitor leaking problum.. pulled the TCU looked perfectly fine to me no leaks no burns looked bran new.. whent ahead and replaced the c28, c35,c32 capasitors just to be sure. i have tryed the pull the fuse and the remove the negative battery trminal to reset the TCU memory this does not seem to do anything some peopl have said that the problum will go away for a short wile if you do this sometimes my goes away then returns sometimes it never goes away at all. im still geting code 7 for the shift silinods even thou i have replaced with new ones .. and have hard tested new ones they are working

 

every once in a wile when in park the motor will idle up and then down rapidly. but has not done this in quite some time. had almost forgoten about it doing that

 

Your problem could be the wiring.

You may want to grab volt meter and see if the resistance to ground of the blu/yel wre at the shift solenoid electrical connector is the same as the resistance to ground at the proper pin of the TCU. The pin is A5 on the TCU and the wire color is blu/yel.

 

ok borrowed a volt meter, there are two wire's at the shift silinod a blue with white stripe, and a green with white stripe.. never use a volt meter befor assuming i just connect 1 wire to the silinod wire and atatch the other to a grounded part of the car.. then repeat on the same wire at the TCU ? then compare results

 

That is correct. Set volt meter to ohms, horseshoe looking symbol. The range is 12-24 ohms. Not sure about your meter, but the range number you want should be larger than 24, but the closest number.

10 would read from 1-10; 100 would read from 10-100, etc...

The red volt meter lead goes to the electrical connector wire. The black lead will go to ground (like a valve cover bolt). Really any bare metal will work for a ground.

 

ok im geting a reading of 23 at the silinod. but have a few questions befor i test at the TCU. there are 2 pluggs on the tcu not sure witch pin is A5 .. also do i check it wile the TCU is pluged in or unplug and test?

 

if you have any type of wireing diagram for the TCU so i can be for sertain im testing the correct wire would be vary useful

 

ok i have removed the mounting plate over the tcu, ecu. and have them hooked up just laying in the floor board for easyer acsess. wile doing this i had the key in turned to the on position listing to the radio. noticed the LED on the TCU was blinking. it's reading 2 code's code 7 and code 8... so i turned key off jumpered the blue conector turned key back on to see what the S light was reading. with the conector jumperd the S light is only reading 1 code, code 7........ not sure if this makes any differance at all.

 

looks like i have another problum with the car i have to fix as well, on the way home from work heard a pop followed by smoke / steam comeing out from under the hood. i found a crack in the top of the radiator on the black domed part just below the radiator cap.. temp gage never registered hot when it happend and never over heated during the mile and half ride rest of way home... hopeing it just failed due to old age and being under pressure... have to fix this first so the car is driveable but am still working on the origonal flashing S light problum..

 

belive all problums solved... replaced radiator easy fix and obious, as for the silinod wire i got a length of wire atatched to the ground on the volt metor attached other end to the conector at silinod harness, used the red wire of volt metor to systimaticaly probe the connector at the TCU till i found the proper wire completing the circle did the smae for the second wire to the silinod the wire's checked out ok so i whent back to the TCU everything seamed to be pointing to it..... pulled and inspected seams when i replaced the bad capasitors i was not as carfull as i should of been i had 1 solder joint a little heavy and it was causeing a short on the board, creating the same symptom's as the bad capsitor. removed solder cleand an resoldered much morer carfuly this time.. so far drives and shift's perfectly... only thing it has done now is when i first started it idled up and down sparaticaly agin ... drove for a few and now the idol seams fine ... time will tell if its just temp or acualy fixed this time