Natural gas heater. See and hear spark. All wires are intact. Turns on from cold start no problem then heats for a few mins turns off then tries to reignite. I see the pilot sparking and lighting but the burners dont ignite and the pilot shuts off then tries to ignite again but pilot just lights for a spilt second then tunrs off. Then cycles again. Display shows SPK and CFH. Only error codes. Cleared burners and all debris and soot. Cant think of anything else to do. Im guessing its the PC board. Any other suggestions out there?