Status LED flashes twice repeatedly, furnace will not run, inducer may not start

Safety: Turn off power to the Trane furnace before opening any panels.

Steps to check:

• Inspect pressure switch tubing: Remove the front panel. Locate the round pressure switch connected to the inducer housing by rubber or silicone tubing. Remove the tubing and check for water, debris, or cracks. Blow gently through the tubing to clear any blockage and reinstall firmly.
• Check vent and condensate: For high-efficiency Trane furnaces (PVC venting), inspect intake and exhaust pipes outside for obstructions (leaves, nests, snow). Ensure the condensate trap and drain lines are not clogged, as water backup can affect the pressure switch.
• Test switch operation (advanced): With power off, disconnect the wires from the pressure switch and check continuity with a multimeter. The switch should be open with no inducer running. If it reads closed, the switch is stuck and should be replaced.
• Reset power: Restore power and call for heat. Confirm the inducer starts and the code clears.

When to call a professional: If the pressure switch tests closed when it should be open, or if the code persists after tubing and vent checks, have a technician replace the pressure switch or diagnose the control board.