Trailer wiring not working

[handstr]

Had the great idea to wire some rigid reverse lights into my trailer harness, but found out it doesn’t work. Plugged a tester into and the 12v works but nothing else. Brake, turn, reverse all won’t work. Any ideas ? I check the fuses under the hood and all were fine.

 

[Doubeleive]

Had the great idea to wire some rigid reverse lights into my trailer harness, but found out it doesn’t work. Plugged a tester into and the 12v works but nothing else. Brake, turn, reverse all won’t work. Any ideas ? I check the fuses under the hood and all were fine.

not sure if this is still the case with the new trucks but on previous models you have to connect the trailer wire power up by the underhood fusebox 1 of the wires would be tucked on the side between the fender and fuse box (wrapped with tape) and other would be tapped up to the main wire harness on the other side in the engine bay area.
they would connect to corresponding post's on the forward side of the fusebox
1 is for power and the other 1 for brake, I wired some reverse lights to my 2012 thru the tow harness and they wouldn't work until I connected those wires

 

[Fless]

not sure if this is still the case with the new trucks but on previous models you have to connect the trailer wire power up by the underhood fusebox 1 of the wires would be tucked on the side between the fender and fuse box (wrapped with tape) and other would be tapped up to the main wire harness on the other side in the engine bay area.
they would connect to corresponding post's on the forward side of the fusebox
1 is for power and the other 1 for brake, I wired some reverse lights to my 2012 thru the tow harness and they wouldn't work until I connected those wires

^^This for 12v auxiliary power, and brake controller circuit. And fuses might need to be added for those.

This is a 2021+ model year? Need more detail on what your truck is.

If these newer models are like the older models, there are individual fuses for the trailer lights, separate from the truck lights. There may be left and right trailer turn signals (brakes) and running lights. Be sure you're looking at those in the fusebox. SWAG maybe they leave those fuses out of those from the factory?

 

[handstr]

It’s a 22 suburban with max trailer. I would expect everything to be hooked up and ready to go. I checked the obvious fuses under the hood. Example trailer left turn but not even that one is working. I bought a 7pin plug in that tells you what lights are working and only the 12v is lit up.

 

[gooffeyguy]

It’s a 22 suburban with max trailer. I would expect everything to be hooked up and ready to go. I checked the obvious fuses under the hood. Example trailer left turn but not even that one is working. I bought a 7pin plug in that tells you what lights are working and only the 12v is lit up.

Was the vehicle started when checking the lights?

I know my brake and turn signal lights won't come on unless the engine is running

 

[handstr]

Yes vehicle was started. And the ground works bc I put a small led prob on the 12v and ground and it lit up.

 

[R32driver]

If it was mine I would have it back at the dealer to see what the deal is. Brand new rig with max trailer package you should have no reason to be troubleshooting wiring. I towed with ours a while back and no issues, all my trailer lights worked like normal

 

[Doubeleive]

It’s a 22 suburban with max trailer. I would expect everything to be hooked up and ready to go. I checked the obvious fuses under the hood. Example trailer left turn but not even that one is working. I bought a 7pin plug in that tells you what lights are working and only the 12v is lit up.

so you have a oem trailer brake controller on the left side of the dash? or no?

 

[Doubeleive]

Was the vehicle started when checking the lights?

I know my brake and turn signal lights won't come on unless the engine is running

should only have to have key-on

 

[handstr]

so you have a oem trailer brake controller on the left side of the dash? or no?

Yes