Hello,
It sounds like you have a problem with the smart junction box SJB. This is what controls the trunk release. Here is a wiring diagram of the SJB so you can see. Also I have included the location of the unit. A shop or the dealer will need to program it for you.
SJB location (below)
Check out the diagrams (Below)
Please let us know what you find. We are interested to see what it is.
Cheers, Ken
Images (Click to make bigger)
Thursday, December 7th, 2017 AT 7:16 PM