So, I also have a 1995 Odyssey EX (only OBD-1, not OBD-2). My D4 light now starts flashing steadily after I drive and start to reach about 25 mph. When I stop and turn off the car and then restart the car, it won't start flashing again until I again start to drive and hit about 25 mph.
I jumped the OBD-1 test connector and turned the ignition switch to accessory, expecting the D4 light to go on and flash a code pattern. But the D4 light did nothing. There was no blinking check engine light either.
Since the transmission control module is apparently not registering and storing an error code, do you think this means that the transmission control module is faulty? Note that I just recently had to replace the ECU/PCM since it was shot and not issuing a signal to the fuel pump to turn on...but this flashing D4 issue was also happening with the previous ECU as well. Or is there something that I'm missing here and does a tranny shop have the ability to read a transmission error code that I cannot using the above method?