Many ECUs do not support reading firmware over CAN, but since automotive manufacturers make mistakes and need to fix firmware bugs, they release firmware updates and support writing firmware over CAN. This will be a deep dive into how you can obtain these firmware updates, decrypt them, (modify if you like) and flash a firmware update file for Honda ECUs. The ECU tools provided by automotive manufacturers are from the stone age, so let’s use a modern web browser to flash an ECU!