The OKI 66207 reads the firmware from a 27C256 EEPROM (32kByte).
![usb 27c256 eprom programmer usb 27c256 eprom programmer](https://ae01.alicdn.com/kf/HTB1w1bAKXXXXXbGXFXXq6xXFXXXv/Env-o-Gratis-Nuevo-Universal-EPROM-EEPROM-flash-mpu-pic-Programador-para-coche-c-mara-usb.jpg)
Technical details: The Honda ECU uses an OKI 66207 microcontroller running at 10MHz. So please do not comment I can just buy something of the shelve: this project is for educational/entertainment purpose. I was thinking of building my own EEPROM emulator, because I want to refresh my PCB / SW / HW knowledge a bit. You can buy the Moates Demon/Ostrich or the Hondata S300, but these cost well over 200$. To solve this there are quite a few EEPROM emulators which allow live updates to the emulated EEPROM for a PC.
![usb 27c256 eprom programmer usb 27c256 eprom programmer](https://m.media-amazon.com/images/I/418mn0Q8PeL._AC_SS450_.jpg)
This is a cumbersome process as with every change you need to stop the car and update the EEPROM. Recently I have been tuning a Honda car with an EEPROM burner.