Originally Posted by WhyMe
take the door off and press the safety switch in to activate the furnace. watch what it does. see if the inducer is rotating. if not check the wires to it.
+1 on watching the furnace start up sequence.
These codes are a guide only, just like OBDII codes. They may not neccecerily mean part failure.
The furnace in my in laws hause, for example, will develop a fail to restart at the beginning if the heating season almost like clock work. I forget the code it throws now because I know what is wrong with it and it's the same thing every time.
Basically the inducer housing does not drain properly for some reason, it's not clogged or anything, but I guess it doesnt drain fast enough and this happens shortly after firs activation from summer break. All that needs to be done is disconnect the small drain hose, let the water drain, blow into it to expel more water and then the furnace will work fine for the rest of the heating season.
But to diagnose it the first time, I had to observe the furnace startup up sequence. In this case, the inducer motor would start spinning, then it would stop, then resume and after a third time I believe it would stop and throw an error code. It never got to turn on the flame. Also, as the inducer motor would wind down, I could hear a sloshing sound of water.
In my previous house, the furnace experienced a similar thing, with similar start up sequence, but I found no water and further diagnosis and googling pointed to a failed pressure switch which apparently was common for this model. The furnace was still under warranty so I called the company and the tech that showed up almost right away, after watching the start up sequence, got to check the pressure switch. It turned out to be bad.