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YP9C - Diagnostic Codes/Fault Codes

Article ID: 598
Last updated: 8 Feb, 2019

York Gas Furnaces: YP9C

Re: Diagnostic/Fault Codes

These York modulating 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:
1 Green Normal Operation - no call for heat
2 Green Indicator for "No error codes in memory". See Diagnostic Fault Code Storage and Retrieval section below.
3 Green Indicator for "Error codes cleared from memory". See Diagnostic Fault Code Storage and Retrieval section below.
Rapid Green Control is in "Factory Speed-up" mode. This mode is used only during factory run-testing of the furnace. To stop this
mode, cycle power to the furnace off and then back on.
1 Amber Normal Operation - with a call for COOLING
2 Amber Normal Operation - with a call for HEATING
3 Amber Normal operation, burner is on at end of heating cycle after wall thermostat has been satisfied.
4 Amber Heating capacity is reduced due to restriction in the circulating air system.
  • Check for dirty filter or closed registers.
5 Amber Heating capacity is reduced due to restriction in the combustion air or vent system.
  • Check for blocked vent/air pipe or clogged condensate drain.
6 Amber Normal operation with call for HEAT PUMP heating.
Rapid Amber Low flame sense current.
  • Check for dirty or mislocated flame sensor rod.
Steady Red Control fault has been detected or there is 24 volts present without 115 volts.
  • Check that there is 24 volts and 115 volts being supplied to the board. If so, then the board should be replaced.
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
  • Bad limit
  • Low airflow
  • Over-Fired
5 Red Rollout switch open / open fuse
  • Bad switch
  • Cracked heat exchanger
  • Bad inducer motor
  • Over-Fired
6 Red Gas valve communication error
  • Bad wiring to valve
  • Bad air pressure sensor
  • Check pressure switch hose connection
7 Red Ignition lockout due to 3 retries
  • Bad igniter
  • Dirty flame sensor
  • No gas flow
8 Red Flame signal lost 5 times
  • Dirty flame sensor
  • Combustion air problem
9 Red Grounding or line polarity fault
  • 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 ID plug is not present or not connected properly

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.

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Article ID: 598
Last updated: 8 Feb, 2019
Revision: 1
Access: Public
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