S3 flashing

[sailboat165]

ok, I'll try and explain this as clearly as I can. I have a 90 prelude with an auto tranny. I start it up in the morning and it runs perfect. I then go where i want to go and shut it off. As long as I leave it alone for long enough to cool down it will start right up again and run perfect. If I want to start it up when it's still hot it will usually do the flashing S3 and won't start. It will turn over but not fire. The S3 flashing will flash forever, it's not giving me any code as far as I can tell, because it will flash continuously, if I leave the key turned on. The check engine light stays on as well. I can go take out the clock fuse and wait, then put it back in, but the flashing continues. I let it sit for maybe 10-15 minutes and when I turn the key on and the s3 light and check engine light go out after a couple seconds, I start it right up and it's perfect again.
If by chance [ and this is seldom] I'm able to start it up when the S3 is flashing, the flashing continues and when I put the car in drive from being in park the tranny will stay stuck in 3rd gear and wont shift up or down like it should. So I either have it in park, neutral, or 3rd gear. So, the problem only occurs when it's hot and hasn't had a chance to cool off. I asked at a Honda service desk and of course they all claimed they had never heard of it before, but suggested I leave it with them for the day, and they would figure it out. I don't think I am the only person that has had this problem and sure don't care to leave it at the dealers so they can ring up big dollars. I appreciate any suggestions anyone can offer.

[spiffyguido]

I think you might actually be having two problems, but do some further diagnostics to be sure.

I'd like you to try and get the error codes from both your ECU and your automatic transmission control unit. The steps to do this are found in the following threads:

viewtopic.php?f=4&t=549

viewtopic.php?f=4&t=706

Let us know what you find. I'm guessing your starting problems might actually be related to the coolant temp. sensor, and the S3 light is caused by the speed sensor, but we'll see.

[sailboat165]

thx for your reply. I will try to see if I can get some codes to happen. So far I can't. I've pulled back the little flap on the passenger side carpet down and it will give me the tiniest little flash once when I turn on the ignition, while looking at it. So I think I'll maybe pull the carpet down further and maybe undo the whole Ecu and see if I can see more of the pretty little red lights that I'm looking for . I do think that it must have something to do with the Tranny because why else would it [ on very rare occasions when I can get it to start while the S3 light is still flashing] want to go straight in 3rd gear when I shift it from park to drive. I do notice that I can get the flashing to end quicker by going under the hood and taking out the ecu fuse and waiting a few seconds and then putting it back in. Often it will clear the issue up even though the engine is still hot and allow me to start it and go.

[spiffyguido]

For the starting issue, there's something that I'd like you to try as I've seen it cause hot start problems many many times.

The next time you can't start the car while hot, open the hood and disconnect the plug on the coolant temperature sensor. It's a two-wire cylindrical plug directly to the right of where the upper radiator hose meets the engine. It's usually a grey or green plug.

With the plug disconnected, try to start the car again, and if it fires right up you may have the source of your starting trouble.

Re: the transmission. You probably have an issue there as well, I agree. Try again to get the trouble code from your transmission control unit following the steps detailed in the 2nd post of the following thread:

viewtopic.php?f=4&t=460

[sailboat165]

well, I don't think that it's the coolant temp sensor. I took the car out for a spin and when I stopped it I had to start it a couple of times while hot and then I got it to start the flashing. I took out the sensor and tried turning on the ignition and it kept flashing. I put the sensor back on and it still flashed. I then left it for about 10 min. and sure enough it went out and it started like normal. I haven't taken the time to get a better look at the ecu light when it's flashing but will get at that in the next day or so. Thx for the advice, I'll take all i can get.

[spiffyguido]

Keep trying to get the error code from the automatic transmission control unit as well.

Take a look at page 9-12 in the 1988 service manual available in our manuals section. It describes how the AT control unit reports error conditions.

[sailboat165]

I took the ECU out a bit [ but still keeping the wires attached] and checked to see if maybe I just wasn't seeing a flashing light that was doing it's thing. I removed the plates covering the computer board . Well i wasn't missing anything and it got me nowhere. All I get when I turn on the ignition is a quick little flash one time on the ECU and it doesn't matter whether the S3 light is flashing on the dash or not. I can get the s3 light to flash by getting the engine all warmed up and then shutting it off and starting it up again and by doing this a couple times I get the s3 light to start it's flashing thing and then it won't start up. I watch the ECU board both, when the s3 goes out as it should after a couple seconds and then starting it up, and also when it's flashing endlessly and the ECU reacts the same either way. I'm starting to wonder whether it is the ECU board itself, since it behaves the same way at all times.

[spiffyguido]

Are you checking the light on the engine control unit (ECU) or the automatic transmission control unit. They are separate boxes. The light on the ECU will flash if the check engine light comes on. The light on the automatic control unit will flash if the S3 light is flashing, as detailed in the manual pages I referenced.

The fact that your transmission still functions at all is a pretty good indication that the control unit for it is working just fine, so it should just be a matter of getting the code.

[sailboat165]

TY for your patience on this subject. I found the box for the AT and got the codes [ finally] They came up as 1. 2 .3 .7. 8. I am seeing from looking at the manual that they are related.

[spiffyguido]

Perfect. Now you have something to go off.

Based on the symptom chart on page 9-14 it looks like you could have a problem with some of the transmissions sensors being unplugged. Take a look at the wiring to all parts of your automatic transmission and see if you can see if anything has suddenly become disconnected. Watch for other symptoms as well...for example, if your speed pulser was disconnected or not working, your speedometer also wouldn't work.

You can use the wiring chart on 9-11 to find out what color of wires you should be looking for.

Sometimes these problems can be as simple as a wire coming undone.