Bcm 2003 350z
 

My rear hatch lock keeps unlocking, has a mind of its own....what is the most inexpensive route to repair?

Perhaps go to a salvage yard to get a new unlock solenoid. ( assuming that it latches properly when closing ). gl!

It could also be the button or wiring. You cheapest option would be to diagnose the problem and figure out why it is happening.

You need to replace the rear hatch trunk actuator (part number 90550-CD00A).

I had to replace this on my 2003 350z last year.