Upon arrival made call for heat and checked furnace. Unit flames came on then shut off suddenly. Cleaned very dirty flame sensor and returned power to furnace. Flames came on and unit ran like normal. Reset power for a second cycle, but unit shut off again after flames. Tried more cycles and was unsuccessful. Code 2 flash related to flame sensor. I believe this flame sensor may still be to dirty to successfully operate in the furnace and should be replaced with new. Upon installation of new flame sensor, further diagnosis may be necessary, and homeowner is aware.
