It should light up. Any fuses blown like power port or lighter? Not sure which fuse powers the OBD port. In my '11 Tahoe on one of the screens that shows fuel mileage it shows V8 or V4 mode. Bring that screen up and see if it stays in V8 mode when light throttle cruising.

 

I never knew that one of the screens would do that. Thank you for the information. I'll do that and check it out.

 

Also be aware, if you don't drive your vehicle much, don't leave the Range device plugged into the obd2 port, it will slow drain the battery. At least mine does.