You cannot turn off the GridLink by yourself. Thats what the vehicle modification is for. Spoof chip, on the other side, may at least confuse Grids further actions, it will take a while to identify the car. Well Agent is already loaded and active.
(You know it isn`t described anywhere AFAIK in the rules how exactly grid works, I play it by my imagination and build on the purpose of the GridLink system) Turning off wireless with your override will Dumpshock Fang, if that was what you are about to do.
EDIT: TBH reading Override in Arsenal, it seems you wont even be able to run on higher than allowed speed without the modification. So my version is even bit less strict (I keep forgetting things. Sorry, Im just a human)...