I have a 2021 Express 2500 Cargo with basic stereo and also has On-Star. I need to locate 12V switched power for Radar detector and dash cam. It seems the fuse box is under the seat. Is there something under the dash I can tap into? I also see a black box to the right of the steering column that looks like a radio or some sort. I am assuming the On-Star. Anyone have any ideas?

 

the procedure is documented in the electrical manuals on gmupfitter.com
Do not tap into existing circuits for power. (signal is OK)
The black box is probably the Telematics Communication Interface Control Module (TCICM) handles cellular and satellite interface. When in doubt, search the part number.

 

Reviewed the electrical schematics and manual. Overwhelming and out of my skill set. I don’t have cellular or SAT in the van. Not even an option on the radio.

 

hire a professional
You have Onstar, so yes you do. See that shark fin antenna on the roof?

 

yes I do. I even see the black box with connections under the dash to right of steering column

 

There's igntion switched power under the drivers under seat fuse box.
https://chevroletforum.com/forum/exp...88/#post470474