The code is a single flash, meaning retrys exceeded.
It will turn on, but once the gas comes on it goes right back off.
The fan spins, the gas comes on, the gas goes off, the furnace turns off.
Please help.

I had a similar issue many years ago and it turned out to be the timed limit switch. I checked the manufacturers website for recalls and it turned out there was a recall on it so I was able to have someone come out with the new part and fix it for free. I'd suggest you might want to check your manufacturers site for recalls before you call in a repairman, for sure.

Good luck!

Didi