My furnace is blowing cold air only. It sounds like the heat kicks on after the initial blowing, only to shut back off. The LEDs indicate pressure switch issue or intake/exhaust issue. Any advice on trouble shooting would be greatly appreciated, if I can get it working without having to call a service tech. Only other bit of info is that my daughter said when the heat was turned on for the first time this season a few weeks ago, the house seemed hazy or smoky for a while. It cleared out and has worked OK since then until yesterday. Thanks!

Check to make sure the vent pipes are not blocked. Make sure the combustion blower is running.