find a 10 year old, and have them start the car, using only the instructions that you have written down.
Are you being sarcastic?
The way i'm wireing is is by having a seperate set of relays, along side the ones the car has. if the car is to be started manually, which will happen most of the time, the arduino has nothing to do with it.
The arduino only controls it's own relays based on the serial command.
Well, like i said, i know very little about C++ or any programming for that matter.
So a little help with the actual code would be nice, if it's not too much trouble?