Can one RPG disable an m1 abrams tank?

Theoretically, one rpg hit directly into the treads of a tank could break loose a tread and render the tank immobile. However, this is very unlikely. The rpg would have to be at least an rpg-9 (rpg-7's being the more common model). And the small area of vulnerability, means that to have a chance of knocking the track loose, a large number of rpg's would have to hit the tank before one got the lucky hit.

A lucky hit to the GPS (Gunners Primary Sight), or other targeting sensors such as the laser range finder could disable the ballistic computer. This would make the main gun far less effective.