so if i put this wire
Battery Constant 12v+ Positive Wire (+): White

and connect it to a module to make it -12v and connect it to this wire:
Power Door Lock Negative Wire Location: In Passenger Side Fusebox

the door will unlock correct?

 

Maybe. Depends on the specific relay wiring.
Single Pole Double Throw (SPDT), Single Pole Single Throw (SPST) Automotive Relays

View the security and alarm applications. Relays can do everything you want.

 

hmm....this is getting much more complicated than i wanted....

I was really hoping i could implement all the hardware on a microcontroller... so when it recieves the signal to unlock itll send the right voltage to the wire to unlock the car

 

well lets just say i wanted to test it out and was by the wiring harness... if i strip the wire for the car unlock back... and i take another wire and tap it to the ground on the car... will the doors unlock??? or am i still on the wrong track?

 

Depends on where you tap the wire.

You are completing a circuit. The lock motor draws current. How much varies, but I would rate a relay for 10A. Negative trigger means you ground the motor. +12V is already available. A relay can be controlled by a microprocessor so that the positive voltage out of the processor powers a relay coil which closes the contact to complete the ground. The motor current is through the relay only.

This is why cars have both computers and relay banks. Relays switch high current. Processors control relays.

 

Start with the wiring/electrical schematic for the car. That will show you where you want to connect. Haynes manuals have good schematics.