13 red flashes High-fire pressure switch open

What the control is telling you

TM9V boards: on a high-fire call the second-stage pressure switch never makes.

Applies to: York/JCI residential gas furnaces: York TM9V

Likely causes

• Partly blocked vent pipe
• Loose or disconnected wire
• Hose problem
• Faulty high-fire switch

Test and repair steps

1. Check vent and intake for partial blockage.
2. Check wiring to the high-fire switch.
3. Check hose from switch to port.
4. Only then replace the switch.
5. To read stored codes with no thermostat call active, tap the LAST ERROR button briefly (under 5 s); up to five codes play back newest first. Two green flashes = memory empty. Hold the button 5 s or more to clear (three green flashes confirm).

Settings for these units

Clearance to combustibles · York TM9V

Leave about 24 in. at the front and 18 in. at the side for service.

Approved for alcove and attic installs.

Filter size by return location · York TM9V

Sizes assume high velocity filters (600 FPM); throwaway filters must stay at or below 300 FPM.

Filters go outside the cabinet - never inside the furnace.

Models that show this code

7 models in York TM9V

Other codes on the same units

• 7 red flashes Ignition failure lockout (retries)
• 8 red flashes Flame lost repeatedly (recycles)
• 9 red flashes Polarity reversed or bad ground
• 10 red flashes Gas valve powered with no heat call
• 11 red flashes Limit open 5-15 minutes - blower failure
• LED steady off Board LED dark - no power to control
• Rapid amber flash Weak flame signal
• Steady on (any color) LED lit solid - internal control fault