Hi :) I have the Trane Furnace that just turn on the gas valve and burn the gas just about 3 second and then stop. No power from the circuit board to the gas valve when it stop burning. LED code is quick flash (call for heat, no error). I though the problem is caused by the flame sensor and tried to replaced the exact flame sensor and then the circuit board but nothing changed. The gas valve is working fine (when it igniting, I connect 24V power supply to the gas valve and it burned until I disconnect).I check that pressure switch and the limit switch, all of them are closed (when the inducer blower is working). The wire connect from flame sensor to the circuit board is good (when I left the flame sensor touch the unit, the fuse burned, that mean the flame sensor is connect to the circuit board, right? :)) It seem to be very easy to tell the the problem is the flame sensor but it's not. Please help Thank you so much

Heating & Cooling - American Standard - Trane Ge Gas Furnace Flame Sensor Sensing Sen00355 Pse-tr9