Here's my problem summarized:

doors locked = trunk alarm activated when opened or unlocked
doors unlocked/opened = trunk alarm not activated when opened

I've performed extensive experiments with my new 2018 EcoBoost Mustang, Sync feature, and I have found that regardless of how I choose to lock the car (remote, outside door handle, inside button), that if I open the trunk with either the remote (by pressing trunk button twice) or going within 3 ft of the trunk with FOB and using the release button above the license plate, that the alarm is triggered until I turn it off with the FOB. If I unlock the car with the FOB first by pressing unlock, I can then freely open the trunk with any method without the alarm sounding. If I unlock the doors by touching the handle or having the FOB close, I ACTUALLY HAVE to open the door before opening the trunk, otherwise the alarm on the trunk will sound.

Is this truly the way this works? Do you HAVE to unlock the doors before accessing the trunk? Am I missing something? My 2012 Challenger has the same locking and remote set up, however I can open the trunk in any manner with any combination and the alarm never goes off whether the doors are locked or not. If the doors have to be unlocked first on the Mustang, the feature of having the FOB close to the trunk (like in your pocket) is of little value as you actually have to take the FOB out to unlock the doors (disarm the alarm) or walk to the door and physically open it first.

I've also thoroughly scoured the internet, ford site, manual and dealership with no success. I also have researched 'Intelligent Access', Sync and all the settings available in the programming options.

If this post is in the wrong location or there is a better location, pls. let me know.

 

no idea, sorry,
but my 2006's doors lock every time the trunk opens lol
maybe it's just buggy

or it's haunted!
yeah, your car is haunted

 

Somethings screwy, I open the trunk on my '16 with the doors locked practically every morning and have never had the alarm go off.

I'm with gravydog316, have you tried washing the car with holy water ???

 

Well if my only choices are haunted, door locking on me when I open the trunk, or the alarm triggering on the trunk if the doors are locked, I'll stick with what I've got LOL

 

I'm surprised the dealership had nothing for you, what did they tell you when you told them about the problem ???

 

The dealership wanted to keep the car for a few days to 'figure it out', after I JUST got it and a terrible nightmare of an experience that took 3 weeks to fix. The purchase agreement was that they were going to add the racing stripes for me, did, but jobbed it out to someone and then when I got it (see pictures), it was an absolute mess! None of them were centered, many had pieces ripped off or patched on and the kicker, it was install AND CUT while on the car!!!!!! When they removed the stripes as I insisted, the Roof, trunk and bumper all had deep cut marks in the paint some over 16" long. They had to repaint my factory paint car. So honestly, I don't trust the dealership to help me out if I can find a way to do it on my own first. look close to see the cuts on both sides
extra piece literally laid on top to attempt to make the line look straight
the right of the left stripe is in the MIDDLE of the car
see the cut mark into the car where material was ripped away? At least that part alerted me to what could have lied ahead when they removed the stripes
use the Ford logo in the front window as a center point for reference to see how off centered lines are

 

 

Yah, stripes are a mess, thats brutal.

 

I am getting my car today, so will check actuation of trunk vs. alarm. Those stripes are brutal and that's sad for the damage done to a new car. I have a somewhat sad story to tell as well. The delivery of my car was delayed, as the top had a stitching problem so it was sent out to a specialty shop to be replaced (200+ km round trip) and when it was returned on Friday the dealership found a 1 cm long scratch on top of the right rear fender which was too deep to buff out. Consequently, they had to paint it and it was not ready for me to pick up on Saturday. They are, however, delivering it to my house today, again, with a further 130+ km on it. So when I get my "new" car it will probably have close to 350 km which I didn't get to put on. Very annoying but not nearly as annoying as your stripe fiasco.

 

You GTA guys get a rough going over, no offence, but quite happy I don't live anywhere near there. I'm sure its good once you get there, but between traffic and people...lol