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91 Accord. Green "S" light problems

04-10-2011, 05:42 PM
91 Honda accord. My car will start fine but when I drive it then try to restart it, the green "S" light flashes and will not let it start. Let it set 15 to 30 minutes and it will start fine. Got a used TCU from a 93 accord and drove the car no more than 5 minutes and the "S" light came on, not flashing but car ran fine. I pulled over, put it in park and light went off. Back in any gear and light came on. Turned car off then tried to restart but wouldn't. Would turn over but not start.
I have read alot of threads on this problem. Alot of people point the problem to the TCU itself or speed sensor (I don't think this is my cars problem) or the main fuel relay. If the main fuel relay is faulty (bad solder?), would that cause the S light to come on and send the car into "limp mode" or did I just another bad TCU? Any advise is appreciated.

04-10-2011, 08:30 PM
If the main relay is bad it won't cause the S light to come on or make the car stall. It will only prevent the car from starting. Usually a bad main relay shows signs when the car is HOT inside, open the door/windows for a few min to cool it down and it should start. As far as the S light there is a way to pull codes but I forget how. You could have more than one issue going on.

04-12-2011, 01:58 AM
Well it hasnt been over 80 here in Central CA soo I am not sure if its cause of the heat BUT after driving the car less than 3 minutes the s light did come on (car has never stalled), I pulled over and turned the car off and immediatly tried to restart. Did not happen. I did let it set for 15 minutes with the windows down and then it did start. It was around 70 that day. Sounds like the main relay but since you said the main relay wont cause the s light to come up, should I rule out the main relay?

I know how to check the codes with the jumper wires but I dont have a CEL. Do I have to wait to check for codes only when the S light is on?

thanks Bullshifter. btw your screen name is awesome

04-12-2011, 06:10 PM
I have to correct what I said about coming on in all gears. I start the car up, no S light is on. When I put car ONLY in D4 does the S light come on. Anyway, I pulled the codes and they were 1 - O2 sensor A, 2 - O2 sensorB, 6 - ECT sensor, 7 - TP sensor, and 14 - IAC Valve. The car doesn't run hot and I just put a new IAC valve on it last month. I am not sure where to start first?

04-17-2011, 01:18 AM
Well today, went back to the junkyard and replace the TCU a third time and replaced the Main Relay. I started the car let it idle for 15 minutes, turned it off and it actually restarted!!! A second test. Took it around the block a couple of times, turned it off, and it restarted AGAIN!! Although the S light does come on when I shift it into D4 it does restart when its warm.

Tried to replace the Throttle Position sensor but didnt know how to get it of the throttle body. Its not bolts, screws, alans, or rivots holding it onto the throttle body. Anyone know what I am talking about?

Also, why does the S light come on when I shift into D4? Thanks for you time and advise in advance.

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