What is the gray plug in the middle??

 

It is for a feature you don't have. Most likely traction control. They just make the same harness for all the trucks even if they don't have all the features. Mine has the same setup as yours but I unplugged the spare plug and cut a hole for a usb port.

 

Good to know. Thanks for the info!

 

No problem!

 

It is traction control. Just had mine apart for a new radio and it is the same connector. How ever my traction control and lighter ports are swapped.