I have a Concord 80 plus furnace that lights and burns normally. The burners will kick on several times. After the cycle it shuts off and flashes error code six, system lockout. If I shut the power off it will repeat the cycle and shut down again. When I turn the power on the blower kicks on and after a few minutes the burners light for several cycles I have cleaned the flame sensor with no luck.

Any assistance would be greatly appreciated.