We recently had to replace the battery in our van and ever since then, the computer has been messed up and caused us to fail our emissions testing with sensors not ready. I cannot find any resources on how to reset the computer in the vehicle... any ideas?

 

Just drive it. Yyou need to start and stop the vehicle like 50 times in order for that code to clear. It is a normal code that will occur anytime the van loses all electrical power and the only practcalway to clear it is to drive the van.