I have a honda 94 ex accord..Well I had my transmission replaced like beginning of this year...I was driving last night and shifted to d4 and then like 8 secs later it started blinking..there was no problem with the shifting it shifted perfectly..so I pulled in to the gas station and checked the transmission fluid while it was off and it was full and check it while it was on and there was none..so I started driving again in d4 and it started blinking then the speedometer went from 40mph down to 0 and then went back up to 40 again and repeated..so I stop again..I turn the car back on and it is fine I began to drive this time in d3 and it did not blink nor did I have problems with the speedometer.

i think this is a common issue with Honda and the accord models. unless you are getting any engine warning or seeing problems or losing power I would not worry and ask Honda to reset processor at next service.

Look at 2 concerns...are you driving above 42 mph when you expect the shift into D4? Automatic overdrive transmissions will not shift into overdrive below that speed. Depending on your mileage, a transmission fluid change may be on your scheduled maintenance list...If over 100,000 miles and no record of previous service, you may want to use an additive instead of a fluid filter change. Sometimes on high mileage, problems occur after an attempt to catch up on ****** maintenance:( My best results have been to use the Lucas Oil Companies "Transmission stabilizer" additive. With a warm motor and transmission, you can add the full bottle of the additive without a need to drain the old fluid. This additive is designed to "refresh" the ****** fluid and filters...about $12. at your parts store. Also you may need to clean your throttle body and injectors by direct spray, and gas tank additive. These are the least costly attempts to address both problems. Hope this helps.

It will blink a set number of times to tell you what diagnostic trouble code it has. I would first check the fluid to make sure it is still red in color and not too low just to make sure that your not doing any damage to the transmission by driving it. Then you can get a cheap repair manual like a "Haynes" manual from any auto parts store.
I hope this info helps!~subyguru~

There are 2 boxes under the passenger side floor board! Take the smallest box out and replace. Got mine at Honda salvage yard for $200. Fixed the problem,

The Blinking D4 light means that the transmission computer needs to be diagnosed, because there is a malfunction.

That is a fault indication for your transmission. I am not positive but I think that indicates a fault in your forth gear solenoid. Your transmission is not going to last very long driving it like that. When you stomp on the gas and it does not accelerate, your clutch discs are slipping and burning. It won't take much of that to ruin them. You may want to take it to a good Honda transmission place. I don't know about the older Hondas, but the newer ones don't have any provision for removing a pan and working on them. They don't even have a line replacable filter.
Check your transmission fluid dipstick. If its not a nice "bright" red color, you are probably burning up your clutches. The darker the fluid, the more contaminated it is.

I've had this problem before. You need to find your transmission computer from under your passenger side floor carpet and see if it looks burnt like this inside. If so, when you call the junkyards, make sure they have your exact year and trim of Accord, ie: LX, EX, SE, etc. Take the old one with you. It's important to know if the car has the sport shift button or not also.

D4 is slipping and not engaging. This means you need a transmission. you're losing a gear

you have a transmission fault the D4 light blinks to tell you that there is a transmission problem when the light is blinking the transmission computer put the transmission into limp home mode so it will not shift normally and you should try not to drive it very far when it gets to this stage you need to have the transmission codes check to pin point the problem

D4 is drive with over drive when overdrive switch is press in/on position on shift. Good luck and thanks for using FIX YA