You need to make sure you are hitting them.  

Guardian's System Crash is projected directionally forward in a cone.  It is not like Zephyrs EMP ability or Redox's Caustic Blast which is an AOE in all directions including up and down.  This makes it somewhat harder to aim.

It also has a pretty short range as Gaurdian is more of a brawler, up in your face style mech. 

Yes thanks, I know that it is only in a 90 degree cone in front of the mech, also that it is only a 30 meter range.  But I'm talking about actually seeing the wave pass over them and it not working.  Also, is the system crash suppose to stop killshot mid dash? It always stops my kills hot mid dash, but it only seems to work half the time when I try to do it, I wasn't sure if it was actually suppose to or not. 

If they are in the process of dashing it won't stop them as it doesn't disable movement. It will stop them from starting the ability but once it is cast it will just shutdown their weapons.

Some interesting things you can do with it though are remove Cheetah's placed mines, remove debuffs from friendly mechs like Zephyr's EMP stun and Redox Damage tick from Caustic Blast.  The main problem though is that it doesn't work on yourself so if you are caught in either it is kind of to late.

Ok awsome,  I think maybe the times it has stopped me mid dash are just a glitch, I will try to get a video sometime.  Thanks for the tips.