Wiring diagram help 10 and 20 series references, what do they mean?

[txbandit44]

So chasing a few issues on the Yukon and came across something on the Mitchell wiring diagram I don't understand. In the attached image the wiring diagram keeps referring to a 10 series and 20 series. I have circled them in red. Is this a connector series or a harness series? How do you know which series on the truck? I'm hunting down what I think may be a ground issue. I have several button modules on the truck not illuminated (DIC Steering wheel controls Trailer brake controll and 3 buttons below the radio) and I had a service trailer brake system warning a few days ago. So I'm checking common issues like grounds and voltages before I go throwing parts at it.

 

[Geotrash]

So chasing a few issues on the Yukon and came across something on the Mitchell wiring diagram I don't understand. In the attached image the wiring diagram keeps referring to a 10 series and 20 series. I have circled them in red. Is this a connector series or a harness series? How do you know which series on the truck? I'm hunting down what I think may be a ground issue. I have several button modules on the truck not illuminated (DIC Steering wheel controls Trailer brake controll and 3 buttons below the radio) and I had a service trailer brake system warning a few days ago. So I'm checking common issues like grounds and voltages before I go throwing parts at it.

The series refers to 1/2 ton (10 series) or 3/4 ton (20 series) chassis.

 

[txbandit44]

That's what I suspected but didn't want to assume so. Thanks for the help.