7 pin connector stays on

[ppod456]

New member. I bought a 2022 2500HD Sierra Denali to pull a travel trailer. Since the beginning I noticed that my rear trailer lights stay on and flicker after turning off truck and lights. They only turn off after disconnecting the 7-pin connector.

This happened again when hooking my truck up to a different trailer and did not happen when a friend's truck was connected to my trailer.
Has anyone heard of this? I'm having trouble getting GMC to believe it's a problem and wants to blame the trailers, even though the testers somewhat confirm it.

 

[mornstein]

My 2021 1500 Sierra does the same. My mechanic says that according to the schematic, the circuit is live whenever the trailer is plugged it. Doesn't seem correct to me.

 

[ppod456]

I did some more research and found that this is a security feature settable via the dashboard. Here's how to test it out. When you turn off your truck do not unhook the 7-pin connector right away. Lock your doors and maybe close windows (not sure if that makes a difference). Then unhook the 7-pin connector. You should hear your car alarm. I finally got this verified by my dealer and tried it out. It worked. It's useful if you stop at a store and leave your truck/trailer for a while.

BTW, I went to 3 other dealers before finding the answer. No one seems to know about it.