when I use the key fob it will turn inside lights on or beep but won't unlock. The only way is to use key but can't unlock back doors. None of the doors work. Could it be the jcas fuse. Just trying to keep it running at 398,000 miles.

 

sounds like the electric actuator inside the door is weak.

Have you changed battery in your remote fob?

 

I had to replace all five door lock actuators on my 01 excursion about a year ago. They all went bad within a few months of each other. The fifth being the rear hatch lock. Amazon had them at a good price.