add actuator questions..

my 4wd in my 2006 v6 automatic tacoma is currenty not working.. when you try to engage it the green light for it in the instrument cluster just flashes.. i hear realys clicking in the glove box area.. i have seen where a lot of people have said this could be caused by a bad add actuator and have found a few posts about it.. would this be scanable with a obd2 tool to narrow down the issue ? i have also seen where sometimes this is caused by a loose connection to power the motor in the add actuator. is this able to be resoldered with removal of the black cover while still in the truck ?

thank you for any help...