Need help on how to connect to car ecu.

Hey everyone, so as the the title says i need some help on connecting to the cars ecu, i think i might have it figured out but i am very new to arduinos so i am not sure 100%.

I have a cable that is consult(nissan version of obd, it is different from obd) to USB, with this cable i have being able to write a program in VS using windows form that streams all the information from the ecu to my laptop. Now i want to move this project onto an arduino, i am using the following. Arduino Mega2560, 4d systems screen that will be running on one of the serial ports.

the part that i am getting stuck on and not 100% sure about is plugging the arduino into the ecu. it has to be done over usb.

Would either of the following ideas work.

idea #1 Use a USB to TTL serial cable, connect the consult cable to the USB TTL cable with a female to female USB connector, then plug the USB to TTL into a RX TX 5v GND pin on the board and program it to use the corresponding serial port. this is the cable i would be using

idea #2 use a USB to TTL board and wire it to the arduino mega, plug the consult cable into it, and program it to the corresponding serial port

idea #3 Use a female to female USB connector, plug the consult cable into a USB cable that can plug directly into the USB port already on the arduino mega, and program it to run on serial port 0 i think it is.

Would any of those ideas work ? it 100% need to run via USB.

Cheers in advance :)

So after a bit more research, ive figured out i'm not going to be able to use USB, as the car runs as 12v but the board only runs at 5v.

so i would need to take it from 12v to 5v, then back to 12v to communicate with the car.

now to figure out if i can use r232 or bluetooth