What exactly is the parking brake wire for that I am grounding for the bypass on the d-3 It says in the book that it is for the gps??

Dave

it is for grounding, telling the vehicle that you are not moving.. try searching this has been asked a few times at least before

I have never used my parking brake in my truck so it is really of no use to me i guess.I guess thatis why we dont use it and just ground it out

Dave

well the parking brake is useful, in fact you should have used it. consult your local dmv or even owners manual for your vehicle on properly using it... but yes it is important.