I have installed the wiring to controller correctly and I have attached the two red wires under the hood to the poles on the breaker box. The controller comes on but says no connection to trailer. The same trailer and same brake controller work fine on a different vehicle so it is something with the suburban. Any idea what could be causing the connection to trailer issue or how to troubleshoot it?

The 7 pole plug receptor looks good, has a cover, and is not rusty, etc.

 

check for power at the 7 pin connector....determine what is missing. they have led trailer pin connector testers for $20

Once you know what is missing...start tracing wires

did you need to install a fuse at the ubec ="breaker box"? for the stud you should have power at the stud
you spliced into the blunt cut wiring under the dash to the 4 pins of the brake controller....or did you splice into a factory plug that connects the the under dash fuse box

 

Thanks, very helpful. I did that and everything lights up as it should so I am at a loss. Same controller and trailer work fine on different vehicle. Any ideas?

 

then check for power coming out of the trailer connector. verify truck grd has no resistance to grd.