I put it in g gear D4 and it starts blinking

Hello,

When the D4 light flashes, it indicates an error form the transmission control module (TCM).
In order to know what the error might be, you will have to retrieve the transmission code(s). That can help with the diagnostics.
To pull the code, remove the kick panel on the passenger side and look for a set of wires with blue connector.
Use a jumper wire between the two pins (can be done using a paper clip or piece of wire).
Turn the key to the on position.
The D4 light will flash the code.
Short flash equals 1 and long flash equals 10.
Add the numbers to get the code.

https://www.2carpros.com/articles/honda-car-1990-1995-obd1-code-retrieval-procedure-and-definition-table

I have attached the code list below.

I have attached diagrams for your reference.

Please let me know if you have any questions.
Thank you.