My keyless entry fob got real hard to work so I put a new battery in it. Now it don't work at all. Please help?
Does it lose touch with the box when the battery is removed?

 

battery installed correctly?

 

Yeah installed the same way the old one was. Flat side + up with rear lid off.
Now the other remote doesn't work either. This is crap.
I wonder if they both need to be reprogramed?

 

Replacing a key remote battery will indeed mean that it needs to be reprogrammed. You're best off calling your dealership and asking them how to do it, or Googling "reprogram scion key fob" or something.

 

my wife's remote was doing the same thing

we replaced the battery..and it worked again for about 3 days..then nothing..we bought another new battery for it..again it worked for a few days

now..it's just dead
the one on my keychin still works though

 

Try this from the tech section:
https://www.scionlife.com/forums/viewtopic.php?t=16563

 

Turns out both batteries were dead and the extra new one I had was dead too. Put new batteries in both fobs and they both work like new again.