Goodman furnace won't ignite.... help.
 

I have a Goodman GMPN120-5 furnace. Tonight I noticed that our house was getting quite cold and found that the furnace was not kicking on. I power cycled the furnace and listened to it's cycle. The exhaust fan turned on (vents though a pvc pipe to the outside) and ran for around 3 minutes and then shut off. I noticed that the ignitor never glowed as it should. I didn't smell any gas. I noticed something that looks like it may be a flame detecting sensor which lies in front of one of the metal tubes where the flame develops. Anyway, I noticed it looks pretty caked up with soot.
I checked the computer board in the furnace and the diagnostic light blinks three times, pauses and then repeats with three blinks then pause and so on.
I don't recall ever replacing the ignitor. It doesn't appear to be defective from what I can see. If I knew what the three blinking red leds represents that would help.
Any other ideas I should try?
It's supposed to get down in the teens tonight, so I need to get this fixed quick!
thanks

I think the light codes are listed inside the blower door.

igniter heats up after inducer motor comes on,check your igniter for a crack.it will probably looklike a white line across one side.