After the break, Fernandez was in action again and made a great save this time to deny Mike Magee, turning his effort past the post after Dallas had lost possession inside their own box.
The game finally sprung to life when Leonardo was sent off for hauling down Bias Perez in the penalty area and the home side were awarded a spot kick.
The roles were reversed minutes later when Jose Villarreal was brought down by John and the Galaxy were awarded a penalty of their own.
But again the penalty was squandered away as Fernandez made a good save by diving to his left to keep Landon Donovan's spot kick out.
This proved to be crucial as five minutes from time John headed home from close range after Matt Hedges had hit the crossbar from a corner to earn his side the points.