1993 Honda Accord Wagon - "D4" dash light is lit and I'm missing 1st & 3rd gear. I reset ECU & D4 light will go out and I have all gears and shifts fine. Turn car off and/or after # of miles light returns and only have 2nd & 4th gear?? Any suggestions would be appreciated. ECU? TCU?? Thanks

 

Check for transmission codes and post them on here. It is simple to do. You just need a piece of wire or a thin paperclip. There is a writeup in the common diy thread on top of the gen tech help forum to check engine codes. The procedure is the same for transmission codes except you count the flashes of the D4 light. There are youtube videos on it too.

 

I also have a Check Engine light - Code #41 Oxygen Sensor. D4 does not flash - either it is on or after disconnecting battery light is off

 

A flashing D4 light means the transmission computer detected a problem and stored a code. Did you try to check for codes before disconnecting the battery? What did the D4 light do when checking codes? Your last post wasn't exactly clear.

 

D4 light on when checking for codes (before reset) - solid on, no flashing. D4 light off after resetting ECU - D4 light back on after short time & few miles - I again checked for codes, no flash on D4 just on solid. Only light that flashed when checking for codes is Check Engine "41".

 

Problem has symptoms of defective TCU. See attached TSB's.

good luck

 

Excellent Thank You!
I do have a 91 EX Wagon parts car with a proper functioning TCU - can I just swap these? Or should I just have mine rebuilt. Both the cars have 125K miles.
Any feedback would be cool.
Merry Christmas!

 

Update - transplant of TCU complete! All gears there & shifts great! Only thing I noticed was radio code when entered would not work. Nice to have all 4 gears all the time.

 

I looked at car-part.com and saw two TCM's listed separately; LX and EX wagons. I suspect you will have problems unless both donor and recipient are LX or EX. There wasn't a large stock of either available used.

I doubt anyone knows for certain what swaps will work. You could try but might wind up w/ two non-working TCM's.

Rebuilding your part may be safest path.

PS: Looks like we posted at same time. Glad to hear it worked out!

good luck

 

Yes, normally the ECU and TCU need replaced with exact part no.