I usually use the scientific approach to begin with: If the wires in the controller are different colors I would check to see which wire is used for zone 2...then look in the valve box for the same wire. If that doesn't work, turn the water off to the sprinklers, turn zone 2 on manually WITH the timer...wait 5 minutes...and feel for the hot buzzing solenoid.
Then you can rebuild (hopefully) that zone to fix your problem.
Good Luck
Sprinkler Solutions, Inc.
Arizona and Colorado
www.sprinklersolutions.net