Can't see trailer connected

I replaced my trailers 7 pin connector and now my truck (2021 Tundra) doesn't see the connection. Everything else works lights wise. My question is what lead from the trailer tells the truck its connected ? Is it the electric brakes ? It worked yesterday when I came home from a campout but I realized the lights were incorrect and I fixed that but now no connection. Also the trailer is not on the ball only connected only through the cable. Thank you !

 

I am not an expert, but You can try and match to this! You are looking for trailer brake output.

 

Some trailers like RVs have to be grounded to the truck through the truck's frame. I recently bought an RV and wanted to check the lights before hauling to the hunting ranch without hooking it up to the ball. I ran a set of jumper cables from RV frame to truck's hitch to test.

 

Thanks Guys, I went and hooked my truck up to my friends trailer and it works fine. Guess it's time to hit the RV boards to see if anyone there has any ideas.

 

You need to be careful with that as supposedly a short in the trailer side can blow some electronics in the instrument cluster. There is a thread on that somewhere around here.

 

Thanks, the issue is resolved and it was a shorted brake magnet. Also interesting fact is that the brake controller is looking for at least 6 ohms of resistance to show the trailer connected.