2015 GMC Terrain, Compustar CM-900AS

Hello to all I have 2015 GMC Terrain I have had a compustar remote start alarm hooked up for a couple months. I changed the battery and now I can’t get the car to start or even crank I have power to all things except the lights inside the car do not work. Is is a it is a CM-900AS with BL I have checked all fuses in the car any help would be much appreciate

It's very unusual for a properly installed Compustar system to brick a vehicle after a simple battery replacement. I would definitely check the vehicle fuses and fusible links closely before jumping on the R/S system.

That being said...

Did you do the install yourself? Wondering how familiar you are with the system. Below is a current diagram of the Blade AL install for your vehicle :



To test to see if the R/S system is causing the issue you could pull the two fuses, unplug the black 20 pin Blade harness and reconnect the one cut vehicle wire ( circled in red ).

-------------
Soldering is fun!

I did not do the install my issue is I can’t see any other fuses other than the one close to the cm900as brain I can’t seam to find where the other things are

A blown fuse on the CM900 wouldn't cause your issue.

Not sure on your next step. If you feel comfortable with taking a few trim panels off to get to the R/S and the vehicles BCM, you could try the above posted test.
If the CM900 20 Pin Blade harness was loose or unplugged you could get the "no start" condition. Not sure how that could happen with a battery replacement. With that one vehicle wire cut, you can't just simply unplug and remove the CM900 controller.

While the wiring is not exactly the same, below is a diagram of the vehicle and BCM location with its necessary connectors indicated.   Use as a quick reference.



-------------
Soldering is fun!

Thanks for the info I will give it a try

check the 2amp Pk3 fuse.. when you slide the key into the ignition and turn it to "ON", and with the door open, do you hear the "ding" ?