Trunk opening when shifting through neutral

[theonenandrew]

I have a 1999 Buick Century Limited with a key fob and a trunk release button in the glove compartment. Recently, the trunk will open when I shift into neutral from park to put it in drive and sometimes it will open when I shift back into park when the doors unlock. I can here it opening as soon as I shift into neutral. I had the car for a few months and just today was the first time it started happening. I just want to know what the problem could be and how to fix it. Thanks!

 

[Spriteman]

The trunk actuator is being energized somehow by the PNP switch circuit. It sounds like a short circuit somewhere that's causing this.

I would chase down the wires from the trunk actuator inside the trunk right at the back of the key slot and see if you see any nicks in the wires or maybe even a bad ground.

You might also try checking the fuse block for any problems.

After checking a circuit diagram it looks like it may be the Body Control Module (BCM) causing this problem. It's the only place that I can see where those two systems have something in common.

Here's a test - first, do you have an owners manual? If so, find the section on programming your door locks when you put the car in Park or Neutral.

There are 4 modes for this - your car is probably in Mode 3 or 4. Change that to be Mode 1 - this tells the car to not unlock any doors when put in park or neutral.

See if that changes the trunk opening.