I just installed a new bcu and ecu and a new key fob came with them. Allegedly the fob was already sync'd to the bcu but it isn't working. Is there a procedure for reestablishing a connection with a fob that was at one time sync'd?

 

Not that I am aware of.

I just sold a set with 2 synced remotes that had been on the shelf for 6 months at least and the buyer installed and both remotes worked without issue.