Upon arrival, thermostat is in off mode. Turned thermostat to heating and set to 90f. Inducer motor comes on instantly as it should. Approximately 10 seconds later the ignitor comes on, and Approximately 5 seconds later, the gas valve opens and the gas is ignited properly. Approximately 3-5 seconds after ignition, the gas valve shuts and the system shuts off. Visual inspection of flame sensor indicates that it is very dirty and possibly not letting the flame seating current to make proper contact. Remove, clean, and replaced flame sensor. Inspected burners to verify they are not rusted or and also causing connection issues. Turned the furnace back on and test ran in heating from thermostat. Furnace comes on as it should and flames stay on thus time. Tested system for 15 images with no issues. Checked Amp draw of both blower and inducer motors, gas valve is getting proper 24v, and pressure switch is satisfied. No other issues detected during testing.