OK, you have the Keyless Entry system. The owner's manual shows the following two notes about opening the trunk. If your external trunk request button was original equipment on your car - it should work under these conditions... But I admit I don't know what the "front passenger inside lock ****" is. And even the cancel switch instructions are slightly confusing. Seems like the switch needs to be in the "on" position for the dash button and external request button to open the trunk. Cancel, on? Oh well. Maybe try it both ways. FOB trunk button should continues to work with this switch in either position.

 

I knew you were thinking about this from a sedan mindset which is why I added my previous comment. The OP has a coupe. Once again '03-'05 coupes did not have an external trunk switch anywhere. If his tail lamp has one it's because either him or a previous owner did the very common upgrade to the '06-'07 tail lights, and the '03-'05s do not have the wiring to support that trunk opener!!!

 

D'OH! Sorry. The 2005 G35 sedan and coupe share the same owners manual. I thought I was looking at coupe info there but obviously from the drawing that was referring to the sedan. Sorry! Your theory about the OP's 2005 coupe having a replacement 06+ left rear lamp seems the most logical answer. That button is likely not connected to anything.

 

There are separate FSM for both the 2005 coupe and sedan. The coupe one doesn't even show a picture of the tail light trunk opener in section BL.

Looks like you might be able to pick up a 2006-2007 passenger door lock actuator and use it to add the tail light trunk button. I don't think the 2003-2005 door lock actuators had the second set of pins for the lock/unlock switch.

All the trunk release is a ground source signal, when the BCM sees ground it opens the trunk actuator.

One side of the tail light switch goes to chassis ground, the other side goes to the passenger door lock actuator switch, through that switch up to the line side (blue wire) of the cabin trunk opener switch, then to the cancel switch in the glove box.

You could look at the tail light harness B125 and if there's no wires landed on pins 4 and 6 then it's not hooked up.

It should be fairly easy to add that circuit, especially if the earlier model passenger door actuator already has pin 2 and 3 on it. Might be as simple as just pulling a wire up to the door, then from the door across the dash to the cabin trunk button.

 

Correct, and as I previously stated there will be no wire on pin 6 of B125. There will be for pin 4 as it's a ground used by all versions of the lamp.

 

ok so if i understand this in idiot terms ( because im no electric guy) absolutely no 05 came with the tailight switch? and if thats true couldnt i just intercept the power wire that goes into the actuator at the latch ofthe trunk and run it over to the taillight switch? or would that mean it could be opened anytime by anybody walking buy unless car is locked ????

 

Let me try to make up for my earlier errors... as cleric670 suggests, you could modify your car so you can use that switch but it's not quite as simple as connecting it directly to the trunk actuator because you don't want the switch to work when the car is locked. That's why the circuit diagram shows the wire from that rear lamp button running to the "Passenger Side Door Lock Assembly". That's where the circuit is either connected (when both doors are unlocked) or disconnected (when the passenger door locked). It corresponds to your "Fuel Lid Lock Actuator" which only unlocks when the whole car is unlocked. Make sense?

So yes, there should be a way to do it, but if I understand correctly it would require a wire run from that button all the way into the passenger door.

The other thing to do is to just pretend that button isn't there and continue to use the fob as your '05 was originally equipped.

 

im thinking that sounds like a splendid idea......thanks for all of your thought's ideas and knowledge i will just tell people its an option.....optionally challenged

 

Yeah it would require running a single wire from the taillight up to the passenger door lock actuator, connecting it to the actuator (using a newer 2006-2007 actuator if the 2005 didn't have the correct pins), then coming back out of the actuator and running another single wire across the dash over to the trunk release button on the driver side, then splicing into the line side of that switch.