91 tcu swap with a 93?

[Mellowdagr8]

Hello everyone! Well first of all I'm new.

I'm not very mechanically inclined but I prefer to do things myself.

I recently purchased a 91 Honda accord ex...the s light was blinking and it felt as though it wasn't shifting properly. My uncle thought it was the transmission but I assumed it was the tcu after reading things online.

So today I went to a junkyard and pulled a tcu from a 93 accord for like $25. I put it in and It shifts better now but the S light stays on when it's in D4.

Was it wise to put the tcu from the 93 in my 91? Any suggestions as to what it could be?

[deevergote]

*sigh*

The flashing S light is telling you of an error code. Something is wrong with your transmission, and your TCU was telling you about it.

The 92-93 models do not have that Sport mode. The 92-93 TCU doesn't know what to do with the wiring, so the S light stays on. You'd be better off getting another 90-91 TCU. Or just use your old one, which was probably fine. Pull the error code, and fix the problem it's reporting.

[Mellowdagr8]

Prior to me Replacing the tcu the car would not shift out of park without an override and would not drive past 55 mph...it did not shift properly.

But I'll put the old tcu back in and pull the codes.

[deevergote]

It's possible that the TCU is bad, but don't just assume so until you pull the codes. If it works well enough with the 93 TCU, I don't think it'll hurt anything to continue using it until you can find a proper 90-91 TCU to replace it. I'm not sure how the 92-93 TCU will report error codes in your 91... it does it by way of the D4 light in the 92-93, but I don't know if the wiring is different with the 91. Best not to mess with it.

[cloudasc]

It's possible that the TCU is bad, but don't just assume so until you pull the codes. If it works well enough with the 93 TCU, I don't think it'll hurt anything to continue using it until you can find a proper 90-91 TCU to replace it. I'm not sure how the 92-93 TCU will report error codes in your 91... it does it by way of the D4 light in the 92-93, but I don't know if the wiring is different with the 91. Best not to mess with it.

The 90-91's have a dedicated sport light, 92-93's, the d4 light bulb is wired in its place. 92-93 Tcu's are a comprimise between the two modes found in the 90-91's. If you use a 90-91 tcu in a 92-93, you will most likely be in "regular" mode all the time. If you use a 92-93 tcu in a 90-91, the sport button on the shifter will do nothing. If you want it to work in a 92-93, you would have to wire up a dedicated switch.