I dont know your particular furnace, but if you initiate call for heat with the burner box open do all of the burners light and burn a nice blue flame? If they do, I would clean the flame sensor lightly with fine steel wool, put it back and initiate the ignition sequence. If you have the type where the ignitor and flame sensor are close together, check the flame hood to make sure it has not warped, and make sure the flame sensor is in the flame envelope.
If Yuri or the other HVAC Pros come on they will be able to tell you more accurately, as they know the particulars to most every brand of furnace out there.
Meanwhile, try what I said above.
If Yuri or the other HVAC Pros come on they will be able to tell you more accurately, as they know the particulars to most every brand of furnace out there.
Meanwhile, try what I said above.