RV Repair: Atwood Water Heater GC6AA-9E, pilot flame, gas valve

Question
My pilot flame lights and runs for about 6 seconds then the system shuts down.  This will happen over and over again but the burner will not light.  I have cleaned the flue aligned the burner and the flame plate on the end of the burner.  I am at a complete loss right now. Can you help me?

Answer
Start by suspecting the thermalcouple.  That is the copper thing that the pilot flame engulfs.  

So the pilot goes out after 6 seconds???  Will the burner light with a match.  BE CAREFUL WHEN CHECKING THAT.  

Easy check is ventilation.  Maybe a plugged filter or vent.

Suspect thermalcouple, or gas valve.