04 Chevy Astro Power Window

I installed an xm radio in my company van - works fine. After it was all back together I now realized that the power locks do not work using the controls on the door panels. Not just drivers door but all the doors. The doors will automatically lock/unlock when put into drive/park respectively so it's not the lock module. I checked the fuse and it's fine. I'm now trying to track down the relay that operates the locks via the door panel control. I can't find the relay. My local auto parts store was no help.  Any help in locating the relay or solving the problem would be appreciated.

Thanks Sparky!! That was it. I never thought the cig lighter would be tied into the lock system.  Thanks again.