Furnace short cycles in early morning, then runs fine
The last 2 days, the furnace has been short cycling early in the morning around 4:00am; turning on, then shutting off after a minute, and continues to do this; a minute on, then off, then re-starts for a minute, then off and the cycle continues. Then around 5:00am, it starts running fine and runs fine the rest of the day. For example, at 6:00am yesterday it ran for 25 minutes nice and smooth until it reached the required temperature (while short cycling around 3-4am). Same thing this morning at around 5:30am...ran for 30 minutes until it reached the required temperature (but again this morning was short cycling around 3:30-4am). The problem is early morning at 3:00-4:00am or so.
Any idea what's going on?
Update code 34 seems to suggest flame sensor: