Knowledgebase

TM9Y Diagnostic Codes / Fault Codes

Article ID: 703
Last updated: 20 Apr, 2022

York Gas Furnaces: TM9Y

Re: Diagnostic Codes / Fault Codes

These York gas furnaces have a control board inside the furnace blower compartment that will flash a diagnostic code that shows the operating status of the furnace.

Diagnostic Codes:
Slow Green Normal Operation - no call for heat
Slow Amber Normal Operation - with a call for HEATING
4 Amber No power on "G" during a cooling cycle (power on "Y")
  • Check thermostat and low voltage wiring
Flashing Amber Low flame signal
  • Flame signal below 0.35 microamps
  • Check flame sensor
  • Check gas pressure
Any Color - Steady On Possible Faulty Control or Blown Fuse
  • Reset power - if steady light returns, replace control
  • Steady Red indicates a blown fuse - Check low voltage fuse
1 Red Flame present with gas off
  • Stuck gas valve
  • Shorted flame sensor 
  • Faulty control
2 Red Pressure switch stuck closed
  • Bad pressure switch
  • Inducer fan relay stuck on
3 Red Pressure switch stuck open
  • Bad pressure switch
  • Bad inducer fan
  • Bad inducer fan relay
  • Blocked or restricted vent
  • Condensate drainage issue
4 Red

Limit switch open / open fuse

Limit opened 5 times during a heating cycle (1-Hour Lockout)

  • Bad limit
  • Low airflow
  • Over-Fired
5 Red Rollout switch open / open fuse (Hard Lockout)
  • Bad switch
  • Cracked heat exchanger
  • Bad inducer motor
  • Over-Fired
6 Red

Pressure switch opened 4 times in one heating cycle (1-Hour Lockout) 

  • Bad pressure switch
  • Bad inducer fan
  • Bad inducer fan relay
  • Blocked or restricted vent
  • Condensate drainage issue
7 Red 3 failed ignition attempts (1-Hour Lockout)
  • Bad igniter
  • Dirty flame sensor
  • No gas flow
8 Red Flame was established but later lost - 5 times in one heating cycle (1-Hour Lockout) 
  • Dirty flame sensor
  • Combustion air problem
9 Red Grounding or line polarity fault
  • Look for loose or missing Ground wire
  • Try reversing transformer power
10 Red Gas valve circuit shorted
  • Check gas valve wiring
11 Red Extended limit switch open
  • Bad limit
  • Blower failure
12 Red Igniter failure
  • Bad Igniter
  • Bad board

Fault Code Retrieval:  With no thermostat call push and release the LAST ERROR button.  The LED will flash up to 5 stored fault codes, beginning with the most recent.  If there are no codes in memory, the LED will flash two green flashes.

Clear the Fault Codes:  Push and hold the LAST ERROR button for at least five seconds.  The LED will flash three green flashes when the memory has been cleared.

This article was:   Helpful | Not helpful
Report an issue
Article ID: 703
Last updated: 20 Apr, 2022
Revision: 1
Views: 16
Comments: 0