Why not start by verify power and ground to module that operate the system.

$1 fuse save you time and money on the parts cannon

 

Takes Steve's advice clean up every ground surface to metal and most issues magically disappear. Just make sure you add some fluid film to prevent rust. I had been dealing with electrical gremlins in our 21012 for the last 2 years.

 

We have the same vehicle. The command start can be deactivated from the fob. Give me some time to find what the sequence is to activate it.

 

OK here is the way you can activate and deactivate your factory command start.
Hold both the lock and unlock buttons at the same time for about 5 seconds.
You will see the park lights flash.
If your command start was activated now it will be deactivated.
If your command start was deactivated now it will be activated.
I have had it change from activated to deactivated and vice versa once in a while.
No sense in replacing anything till you know its not activated.

 

 

Thanks very much for all the great advice, greatly appreciated.