For anyone else who might be having the same problem as I had...It was indeed the fan on the combustion blower, it was seized up and needed to be cleaned and lubricated.

Thanks I'll check to make sure the motor and wheel aren't dirty, tubes look to be fine. Appreciate the help!

I have a furnace model DGAT056BDF that worked fine last winter but when i tried to turn it on for the first time this year, it wouldn't start and showed 3 flashing lights for the error code, which on my furnace reads "Combustion air switch failed to close" I couldn't hear the pressure swit...