My trucks been throwing the infamous “service trailer brakes” message in the driver information center. And I found my 30amp fuse blown and I replaced it but that didn’t fix it, so I bought a trailer brake relay (the one that mounts on the frame usually above the rear axel). Well I went to replace that relay and unfortunately I can’t for the life of me find the factory relay location in order to perform the swap. I bought my 2013 3500hd without the original bed it has a flatbed on it with a second gas tank where I’m assuming the spare tire would be. Idk if it’s on the inside of the frame rail above the tank where I can’t see it, however it doesn’t appear to have any keyhole bolts on the frame visible from the outside so I have no clue where this thing is ........ PLEASE HELP vin number is : 1GB4CZC88DF231914