Early this week my furnace when out. It's a Trane XV80 model #TUDo6oRpV3k4 Serial # 5065S9E1G Date of manufactuer 2/05. It has a two stage gas valve. I when down stairs open the furnace door and watch the seq. of operation. The inducer fan comes on and board goes through the rest of the safety until it comes to the ignitor, the ignitor would not come on. So I replaced the ignitor. The ignitor works now and the board trouble light is flashing red fast and constant. Saying normal call for heat. Cleaned the flame sensor, but the gas valve still willn't open. Any suggestion what to do next would be great.

Thanks.