I dont have a manual for it, look onthe back side of your front cover. There may be a troubleshooting guide with the codes.
More then likely it is a inducer pressure switch fault (not necessarily a faulty pressure switch). Most common causes are:
-Blocked exhaust or air intake (bird/wasp nests). Make sure they are clear.
-Plugged condensate drain causing condensate (water) to back up into the inducer blower. Check and clear the lines. There should be water in the trap. (This keeps exhaust gas from escaping)
-Failing pressure switch. These have a membrane that can fail. You will need a hand powered vacuum pump and gauge to test this, too much vacuum from the pump will destroy it. You can often borrow these from big box auto parts stores.
-Failing inducer. The inducer must spin at a specified speed or not enough vacuum will be generated to trip the pressure switch. Bad bearings (condensate is acidic and will speed up rust in the bearings if it backs up into them) is the most common cause. They usually get noisy. This is a whole unit replacement.
Then pressure switch is a safety switch. You can bypass it to see if the furnace starts, but DO NOT RUN THE FURNACE WITH IT BYPASSED. You could be putting you and your family at risk of carbon monoxide (a silent killer) IF it starts, shut it off immediatly and check the above in order.
Sometimes the switch could get stuck from sitting over the summer. Try tapping on it a few times. There may be a button in the back to manual actuate it for testing purposes. If there is, push it a few times with the furnace shut off. Then try starting it again.. If it works, be prepared, sometimes it will never act up again, sometimes its a warning of the switch failing.