Yes, there are actually two separate ones.

One is for the air conditioner condensate, the other is for the furnace itself. That's the one I was referring to. You need to completely disassemble the drain lines and make sure all the fittings and passageways are clear and unobstructed. IIRC, the forced draft has to be able to blow/draw through those drain lines freely or the draft sensor will shut the machine down.

And then again, your furnace problem could be something entirely unrelated to this?