When I start my furnace the burners stay on for 5 to 10 seconds then go out.I check the flame sensor its OK ?

My question to you, is how did you check the flame sensor ? The correct way to check one is with a volt meter set for ohms ( and or continuity ) and with one lead from your meter on the wire end (disconnected ) and with the other meter probe ONLY touch the outer 1 inch of the flame rod, does the meter register a beep, proving continuity ? DO NOT RUB the probe on the flame proving rod to check, because in the flame rectification process, the flame does not rub the rod to prove flame. Usually, corrosion is the cause of a furnace not proving flame through the flame rod ( cleaning it carefully with rough steelwool or sand paper, will clean the corrosion off it )... BUT if it tests OK the cause could be a bad control, not recognizing the flame sense from the rod.