While driving, the D4 light gets bright, it shifts down into 3rd, and continues for a while.It will manually down shift into 1st but thats it.When you manually shift it, the D4 light stays on bright, but the other gears selected illuminates also.It does it very spuraticly, and does not seem to matter if its cold or warm.This car has 230000 miles on it, and I have never had any Trans issues until now.When it is operating properly, it shifts fine, no slippage.Any help will be greatly appreciated!

 

Sounds like the TCU to me. It is located under the floor board on the passengers front seat. I have had to replace several of these over the years with many 90 - 93 accords I have bought and sold. If you can manually shift it and all the gears shift fine I would put maney on the TCU.

 

When It's operating properly, all gears shift fine. When it starts to act up, the only gear I can Manually shift into is 1st. If I shift it up into 2nd it does nothing but slowly slip up into 3rd.The whole time the D4 gear selection is really bright.

 

A good used TCU from a salvage yard is $50 to $75. Just make sure the part numbers and serial numbers match with your old one. This is worth the try before you rebuild a tranny and still have the same problem. I can remember back in the late 90's everyone rebuilding there 90 - 93 model tranny's and still having the same problem afterwards and then replacing the TCU.

 

Hey, thanks for your response. I'm going to look at all the connections at the TCU, then shop around for a used one.Thanks