2013 Sierra 2500 HD doors unlock but will not lock

[Jack Gaskins]

Good morning all, 

I am at a loss, I took my pickup to be detailed and when I got it back the door lock switches will unlock but will not lock. The keyless entry works just fine. I checked fuses, all were good (unless I overlooked one) I pulled both switches cleaned contacts as well as sprayed electrical contact cleaner under the switch and then blew it out with an air hose. I did a 12v test on all the pegs when the button was pressed and there was voltage change however I cannot hear the relay when the lock button is pressed. I cannot seem to locate the relay's. I can hear the unlock relay down in the in cab fuse box area however cannot see/find it. Has anyone ever had this issue? Does anyone have any advice on where to go from here? I contacted the detailer, they claim they did not remove the door panel or anything like that and have never had this issue after a detailing.

 

Thank you in advance for any assistance anyone may be able to provide!