Furnace flame will stay on for 5 seconds and shut off. Led light on circuit board flashes once after it completes cycle. 1 flash indicates the following possible problems: Gas flow... Gas pressure... flame sensor... as a result, everything seems to be working normal. However, I did replace the flame sensor, but I'm still having the same problem.

Model number
Type of fuel LP or natural.

((as a result, everything seems to be working normal. However, I did replace the flame sensor, but I'm still having the same problem))

How can everything be working normal but you are still having a problem?

Be more specific.