York TM9T100C16MP11 Error Code 2 Red Flashes: Pressure Switch Stuck Closed
What Does Code 2 Red Flashes Mean?
A 2 red flash code on the York TM9T100C16MP11 means the pressure switch contacts are closed at the beginning of a heat cycle when they should be open. The control board checks the pressure switch state before starting the inducer motor — if the switch is already closed before the inducer creates any draft, the board knows something is wrong and will not proceed with the ignition sequence.
The most common cause is a faulty pressure switch with stuck internal contacts. These switches contain a flexible diaphragm and a set of electrical contacts that can stick together after years of operation. Miswiring of the pressure switch is also possible, especially if the switch was recently replaced or the wiring was disturbed during service work.
This repair requires a qualified HVAC technician. The technician will test the pressure switch with a multimeter to confirm the contacts are stuck, inspect the wiring for shorts or incorrect connections, and replace the switch if needed. Do not attempt to bypass the pressure switch, as it is a critical safety device.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Faulty pressure switch stuck in closed position | Most common | ✗ Call a pro → |
| Miswiring of pressure switch | Common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- When this code appears — a stuck pressure switch must be professionally tested and replaced
Sources
✓ Verified against manufacturer service manual — March 2026