My 4wd 1998 blazers speedometer stopped working after going crazy and it stopped shifting gears I already changed the speed sensor still have the same problem also door locks locking by themselves really need help here

 

There can be codes to be read associated with the Body Control Module. I'd do that and see what is going on.

That the speedometer stopped working simultaneously with the other components does suggest there could be a connection but I do not know what it would be.

What would also help is some more details on how the speedometer acted and the lack of shifting gears. Also, under what conditions do the door lock on their own?

 

The only code is P0503 speed sensor I replaced it. The speedometer flickered and stopped and it stopped shifting gears. Also door locks open and lock by themselves