HVAC Code Lookup

York and Coleman fault codes

48 documented codes for York and Coleman furnaces, each cited to the manufacturer's own manual. Find your code in the table, then jump to what it means, the likely causes, what you can safely check, and when to call a technician.

York is Johnson Controls Unitary Products (UPG). The same UPG furnace control boards and the same LED flash-code tables are used across York, Coleman, Luxaire, Champion, Guardian and Fraser-Johnston branded furnaces, and Johnson Controls publishes one installation manual per chassis covering all of those model prefixes (e.g. the modulating manual covers YP9C, CP9C, LP9C and TP9C together). There are two distinct code systems: the classic UPG single/two-stage board (TG8S, TG9S, TM8X, TM9X, TM8T, TM9T, TM8V, TM9V, TM9E, TM8Y, TM9Y) which uses 1-13 red flashes plus green/amber status flashes, and the modulating board (YP9C / YPLC and the older Affinity modulating furnaces) which uses a different red/green/amber flash list. That is why Coleman codes are on this page: they mean the same thing on either brand.

Looking it up by flash count?

If you counted LED flashes rather than reading a code number, these are the codes that start with that many flashes:

Furnace codes

CodeMeaningSeverity
Slow green flashGreen LED on two seconds, off two seconds, repeatingNormal operationStatus
Slow amber flashAmber LED on two seconds, off two seconds, repeatingNormal operation with a call for heatStatus
LED steady offNo LED activity at allThe control board LED is not flashing at all, which means the board is not getting power or its on-board fuse has blownWarning
Steady on (any color)LED lit solid, not flashing, in any colorControl failureHard lockout
Continuous green flashGreen LED flashing on and off continuously with no pausesTwinning errorWarning
Continuous red flashRed LED flashing on and off continuously with no pausesTwinning error on the TM8Y / TM9YWarning
Continuous amber flashAmber LED flashing on and off continuously with no pausesThe flame sense current has fallen below 1Warning
1 red flashOne red flash, then a two-second pause, repeatingFlame was sensed when there was no call for heatSafety fault
2 red flashesTwo red flashes, then a two-second pause, repeatingThe pressure switch is closed when it should be openSoft lockout
3 red flashesThree red flashes, then a two-second pause, repeatingThe pressure switch contacts are open when they should be closedSoft lockout
4 red flashesFour red flashes, then a two-second pause, repeatingThe main limit switch has opened its normally closed contacts - the furnace is overheatingSoft lockout
5 red flashesFive red flashes, then a two-second pause, repeatingThe normally closed flame rollout switch has openedSafety fault
6 red flashesSix red flashes, then a two-second pause, repeatingWhile the furnace was running, the pressure switch opened four times during one call for heatSoft lockout
7 red flashesSeven red flashes, then a two-second pause, repeatingThe burners failed to light on three trials for ignition, so the control locks out for one hour and then tries againSoft lockout
8 red flashesEight red flashes, then a two-second pause, repeatingThe flame was lost five timesSoft lockout
9 red flashesNine red flashes, then a two-second pause, repeatingReversed line voltage polarity, a grounding problem, or reversed low voltage transformer wiresHard lockout
10 red flashesTen red flashes, then a two-second pause, repeatingThe gas valve is energized with no call for heatSafety fault
11 red flashesEleven red flashes, then a two-second pause, repeatingThe main limit switch opened and stayed open for more than five minutes, which the control reads as a failed blowerHard lockout
12 red flashesTwelve red flashes, then a two-second pause, repeatingThe model ID plug on the control board is loose or missingWarning
13 red flashesThirteen red flashes, then a two-second pause, repeatingThe high-fireWarning
4 amber flashesFour amber flashes, then a two-second pause, repeatingThe control is receiving a YWarning
2 green flashesTwo green flashes after pressing the LAST ERROR buttonThere are no error codes stored in the control board's memoryStatus
3 green flashesThree green flashes after holding the LAST ERROR button more than five secondsConfirmation that the stored error code memory has been clearedStatus
Steady off (YP9C modulating)No LED activity at all on the modulating control boardNo 24V power at the modulating control boardWarning
1 green flash (YP9C modulating)One green flash, two-second pause, repeatingNormal operation with no call for heatStatus
Rapid green flash (YP9C modulating)Green LED flashing rapidlyThe control is in Factory Speed-up mode, used only during factory run-testingWarning
1 amber flash (YP9C modulating)One amber flash, two-second pause, repeatingNormal operation with a call for coolingStatus
2 amber flashes (YP9C modulating)Two amber flashes, two-second pause, repeatingNormal operation with a call for heatStatus
3 amber flashes (YP9C modulating)Three amber flashes, two-second pause, repeatingNormal operation - the burner is still on at the end of the heating cycle after the wall thermostat has been satisfiedStatus
4 amber flashes (YP9C modulating)Four amber flashes, two-second pause, repeatingThe furnace has automatically cut back its heating output because airflow through the house side is restrictedWarning
5 amber flashes (YP9C modulating)Five amber flashes, two-second pause, repeatingThe furnace has cut back its heating output because the combustion air or vent system is restrictedWarning
6 amber flashes (YP9C modulating)Six amber flashes, two-second pause, repeatingHeat pump applications only: normal operation with a call for heat pump heatingStatus
Rapid amber flash (YP9C modulating)Amber LED flashing rapidlyLow flame sense currentWarning
1 red flash (YP9C modulating)One red flash, two-second pause, repeatingFlame is present with no power being supplied to the gas valve - gas is reaching the burners when it should not beSafety fault
2 red flashes (YP9C modulating)Two red flashes, two-second pause, repeatingThe pressure switch is closed while inducer pressure is below the switch setpoint - the switch is closed when it should be open, so the control will not startSoft lockout
3 red flashes (YP9C modulating)Three red flashes, two-second pause, repeatingThe pressure switch is open while inducer pressure is above the switch setpoint - the switch is open when it should be closed, so the burners cannot lightSoft lockout
4 red flashes (YP9C modulating)Four red flashes, two-second pause, repeatingHigh limit switch open, defective temperature sensor, or the 24 volt fuse is openSoft lockout
5 red flashes (YP9C modulating)Five red flashes, two-second pause, repeatingThe rollout switch or the condensate pressure switch is openSafety fault
6 red flashes (YP9C modulating)Six red flashes, two-second pause, repeatingGas valve communication errorSoft lockout
7 red flashes (YP9C modulating)Seven red flashes, two-second pause, repeatingLockout due to no ignitionSoft lockout
8 red flashes (YP9C modulating)Eight red flashes, two-second pause, repeatingLockout due to too many flame recycles - the flame was lost five times during a single heating cycleSoft lockout
9 red flashes (YP9C modulating)Nine red flashes, two-second pause, repeatingReversed line polarity or improper grounding at the furnaceHard lockout
10 red flashes (YP9C modulating)Ten red flashes, two-second pause, repeatingGas valve circuit shortedSafety fault
11 red flashes (YP9C modulating)Eleven red flashes, two-second pause, repeatingMain blower failureHard lockout
12 red flashes (YP9C modulating)Twelve red flashes, two-second pause, repeatingThe model ID plug is not present or not connected properlyWarning
Steady on red (YP9C modulating)Red LED lit solid, not flashingA control fault has been detected, or 115 volts is present without 24 voltsHard lockout
2 green flashes (YP9C modulating)Two green flashes after pressing the LAST ERROR buttonIndicator for 'No error codes in memory'Status
3 green flashes (YP9C modulating)Three green flashes after holding the LAST ERROR button more than five secondsIndicator for 'Error codes cleared from memory'Status

York furnace Slow Green Flash: Normal operation

StatusShown as: Green LED on two seconds, off two seconds, repeating

Normal operation. The control board is powered and healthy and there is no call from the thermostat. This is the LED's resting state, not a fault.

Manual wording: “SLOW GREEN FLASH: Normal operation, no thermostat calls.”

Documented for: TG8S, TG9S, TM9E, TM9V, TM8Y, TM9Y and other UPG single/two-stage boards

Likely causes, most common first

  1. Normal standby - no heating, cooling or fan call from the thermostat

What you can safely check yourself

  • If the house is cold, check the thermostat is set to HEAT and above room temperature
  • Check the thermostat batteries

When to call a technician

No service needed for this code. If the furnace still will not run with the thermostat calling for heat, have a technician check the thermostat wiring.

Sources

York furnace Slow Amber Flash: Normal operation with a call for heat

StatusShown as: Amber LED on two seconds, off two seconds, repeating

Normal operation with a call for heat. The control has received a W signal from the thermostat and is running the heating sequence. Not a fault.

Manual wording: “SLOW AMBER FLASH: Normal operation with call for heat.”

Documented for: TG8S, TG9S, TM9E, TM9V, TM8Y, TM9Y

Likely causes, most common first

  1. Normal heating operation with a thermostat call for heat

When to call a technician

No service needed. If the furnace is showing this code but no warm air reaches the rooms, have a technician check the blower and ductwork.

Sources

York furnace LED Steady Off: The control board LED is not flashing at all, which means the board is not getting power or its on-board fuse has blown

WarningShown as: No LED activity at all

The control board LED is not flashing at all, which means the board is not getting power or its on-board fuse has blown.

Manual wording: “LED STEADY OFF - If the LED light does not flash at all, check for power to the board and check for a blown fuse on the board.”

Documented for: TG8S, TG9S, TM9E, TM9V, TM8Y, TM9Y

Likely causes, most common first

  1. No power reaching the control board
  2. Blown fuse on the control board
  3. Failed control board

What you can safely check yourself

  • Check the furnace breaker in the electrical panel is on
  • Check the furnace service switch (the light-switch-looking one near the furnace) is on
  • Make sure the furnace door panel is fully seated - a loose door opens the door switch and kills power to the board

When to call a technician

If the breaker and switch are on and the door is seated but the LED is still dark, the fuse or the board itself needs a technician. Replacing a blown control-board fuse means finding what shorted it out first.

Sources

York furnace Steady On (Any Color): Control failure

Hard lockoutShown as: LED lit solid, not flashing, in any color

Control failure. The board has detected an internal fault. On the TM8Y/TM9Y board an open 24V control fuse also produces a steady red LED.

Manual wording: “STEADY ON ANY COLOR: Control failure. Turn power to the furnace off and back on. If the fault code returns, the control board must be replaced. The control board is not field-repairable.”

Documented for: TG8S, TG9S, TM9E, TM9V, TM8Y, TM9Y

Likely causes, most common first

  1. Internal control board failure
  2. Open 24 volt control fuse on the board (TM8Y / TM9Y)

What you can safely check yourself

  • Turn the furnace off at the service switch for a minute, then back on once, to see if the code clears

When to call a technician

If the solid LED returns after one power cycle, the control board must be replaced. Johnson Controls states the board is not field-repairable, so this is a technician job.

Sources

York furnace Continuous Green Flash: Twinning error

WarningShown as: Green LED flashing on and off continuously with no pauses

Twinning error. Two furnaces are wired together on a common duct system and the 24V control power is out of phase, or one of the twinned units has lost power.

Manual wording: “CONTINUOUS GREEN FLASH: Twinning error, incorrect 24V phasing or no power to twinned unit. Check twinning wiring. Confirm that both twinned units have power.”

Documented for: TG8S, TG9S and other twinnable UPG single-stage furnaces. On TM8Y / TM9Y the same twinning fault is shown as a continuous RED flash instead.

Likely causes, most common first

  1. Incorrect 24V phasing between twinned furnaces
  2. No power to the twinned unit
  3. Twinning wiring error

What you can safely check yourself

  • Check the breaker and service switch for the second (twinned) furnace are on

When to call a technician

Twinning phasing is a wiring job. A technician needs to verify the 24V transformer phasing and twinning harness between the two furnaces.

Sources

York furnace Continuous Red Flash: Twinning error on the TM8Y / TM9Y

WarningShown as: Red LED flashing on and off continuously with no pauses

Twinning error on the TM8Y / TM9Y (and TM8T / TM9T) boards: incorrect 24V phasing between two twinned furnaces, or no power to the twinned unit.

Manual wording: “CONTINUOUS RED FLASH: Twinning error, incorrect 24V phasing or no power to twinned unit. Check twinning wiring. Confirm that both twinned units have power.”

Documented for: TM8Y, TM9Y (and the TM8T / TM9T two-stage PSC chassis)

Likely causes, most common first

  1. Incorrect 24V phasing between twinned furnaces
  2. No power to the twinned unit
  3. Twinning wiring error

What you can safely check yourself

  • Check the breaker and service switch for the second (twinned) furnace are on

When to call a technician

Have a technician verify the twinning wiring and 24V transformer phasing between the two furnaces.

Source

York furnace Continuous Amber Flash: The flame sense current has fallen below 1

WarningShown as: Amber LED flashing on and off continuously with no pauses

The flame sense current has fallen below 1.5 microamps. The furnace is still lighting, but the control can barely see the flame and will eventually lock out if the signal keeps dropping.

Manual wording: “CONTINUOUS AMBER FLASH: Flame sense current is below 1.5 microamps. Check and clean flame sensor. Check for proper gas flow.”

Documented for: TG8S, TG9S, TM9V, TM9Y and other UPG boards. On TM8Y the threshold is 0.28 microamps.

Likely causes, most common first

  1. Dirty or corroded flame sensor rod
  2. Poor gas flow to the burners
  3. Weak or failing flame signal path

What you can safely check yourself

  • Replace a dirty air filter
  • Make sure the vent and combustion air pipes outside are clear of snow, ice, leaves or nests

When to call a technician

Cleaning the flame sensor means working inside the burner compartment with the gas on. Have a technician clean the sensor and measure the flame current. Ignoring it usually ends in a no-heat lockout.

Sources

York furnace 1 Red Flash: Flame was sensed when there was no call for heat

Safety faultShown as: One red flash, then a two-second pause, repeating

Flame was sensed when there was no call for heat. The control saw a burner flame while the gas valve should have been closed, so it runs the inducer and the blower to clear the heat exchanger.

Manual wording: “1 RED FLASH: This indicates that flame was sensed when there was not a call for heat. The control will turn on both the inducer motor and supply air blower. Check for a leaking or slow-closing gas valve.”

Documented for: TG8S, TG9S, TM9E, TM9X, TM8X, TM9T, TM8T, TM8Y, TM9Y

Likely causes, most common first

  1. Leaking gas valve
  2. Slow-closing gas valve

What you can safely check yourself

  • If you smell gas, leave the house and call the gas utility from outside

When to call a technician

This means gas may be reaching the burners when it should not. Call a licensed technician right away - the gas valve has to be tested and replaced by a professional.

Sources

York furnace 2 Red Flashes: The pressure switch is closed when it should be open

Soft lockoutShown as: Two red flashes, then a two-second pause, repeating

The pressure switch is closed when it should be open. Before each heat cycle the control checks that the pressure switch contacts are open; if they are already closed it will not allow the ignition sequence to start.

Manual wording: “2 RED FLASHES: This indicates that the pressure switch is closed when it should be open... Check for a faulty pressure switch or miswiring.”

Documented for: TG8S, TG9S, TM9E, TM9X, TM8X, TM9T, TM8T, TM9V, TM8Y, TM9Y

Likely causes, most common first

  1. Faulty pressure switch stuck closed
  2. Miswired pressure switch

What you can safely check yourself

  • Turn the furnace off at the service switch for a minute and back on once to see whether the code clears

When to call a technician

A stuck-closed pressure switch is a safety interlock failure. It must be tested and replaced by a technician - never jumper or bypass it.

Sources

York furnace 3 Red Flashes: The pressure switch contacts are open when they should be closed

Soft lockoutShown as: Three red flashes, then a two-second pause, repeating

The pressure switch contacts are open when they should be closed. The inducer is not producing enough draft to close the switch, so the control will not light the burners.

Manual wording: “3 RED FLASHES: This indicates the pressure switch contacts are open when they should be closed. Check for faulty inducer, blocked vent pipe, broken pressure switch hose, disconnected pressure switch or inducer wires or faulty pressure switch.”

Documented for: TG8S, TG9S, TM9E, TM9X, TM8X, TM9T, TM8T, TM9V, TM8Y, TM9Y

Likely causes, most common first

  1. Faulty inducer (draft) motor
  2. Blocked vent pipe
  3. Broken pressure switch hose
  4. Disconnected pressure switch or inducer wires
  5. Faulty pressure switch

What you can safely check yourself

  • Go outside and check the vent and combustion air pipe terminations for snow, ice, leaves, insect nests or other blockage
  • Check the condensate drain and trap for a clog (on 90%+ furnaces a plugged drain can back up and open the pressure switch)
  • Replace a heavily clogged air filter

When to call a technician

If the outside pipes are clear and the code stays, a technician needs to test the inducer, hoses and switch. Do not jumper the pressure switch - it is what proves the furnace can vent safely.

Sources

York furnace 4 Red Flashes: The main limit switch has opened its normally closed contacts - the furnace is overheating

Soft lockoutShown as: Four red flashes, then a two-second pause, repeating

The main limit switch has opened its normally closed contacts - the furnace is overheating. The control runs the blower and inducer while the limit is open to cool the heat exchanger down.

Manual wording: “4 RED FLASHES: This indicates that the main limit switch has opened its normally closed contacts. The control will operate the supply air blower and inducer while the open limit condition exists. Check for a dirty filter, improperly sized duct system, incorrect blower speed setting, incorrect firing rate, loose limit switch wiring or faulty blower motor.”

Documented for: TG8S, TG9S, TM9E, TM9X, TM8X, TM9T, TM8T, TM9V, TM8Y, TM9Y

Likely causes, most common first

  1. Dirty air filter
  2. Improperly sized duct system
  3. Incorrect blower speed setting
  4. Incorrect firing rate
  5. Loose limit switch wiring
  6. Faulty blower motor

What you can safely check yourself

  • Check and replace the air filter - this is the number one cause
  • Open all supply registers and make sure return grilles are not blocked by furniture or rugs
  • Check that the furnace door panel is fully seated

When to call a technician

If the code comes back after a clean filter and open vents, the airflow problem is in the ductwork, blower or firing rate and needs a technician. Never jumper or reset the limit switch to keep the furnace running.

Sources

York furnace 5 Red Flashes: The normally closed flame rollout switch has opened

Safety faultShown as: Five red flashes, then a two-second pause, repeating

The normally closed flame rollout switch has opened. Flame or hot combustion gas has spilled out of the burner box instead of going up the vent. The control goes into a hard lockout that only a power cycle will clear.

Manual wording: “5 RED FLASHES: This fault is indicated if the normally closed rollout switch opens. The rollout control is manually reset. Check for proper combustion air, proper inducer operation, and primary heat exchanger failure or burner problem. The control will enter a hard lockout...”

Documented for: TG8S, TG9S, TM9E, TM9X, TM8X, TM9T, TM8T

Likely causes, most common first

  1. Insufficient combustion air
  2. Inducer not drawing properly
  3. Cracked or failed primary heat exchanger
  4. Burner problem

What you can safely check yourself

  • Check the outside vent and combustion air pipe terminations for blockage
  • Make sure nothing is stored against the furnace blocking its air supply
  • If you smell exhaust fumes or have any CO alarm activity, leave the house and call for service from outside

When to call a technician

Call a licensed technician before running the furnace again. A rollout trip means combustion gas escaped the burner compartment, which can mean a cracked heat exchanger and a carbon monoxide risk. The rollout switch is a manual-reset safety device and must only be reset by a technician after the cause is found.

Sources

York furnace 6 Red Flashes: While the furnace was running, the pressure switch opened four times during one call for heat

Soft lockoutShown as: Six red flashes, then a two-second pause, repeating

While the furnace was running, the pressure switch opened four times during one call for heat. The furnace locks out for one hour, then tries again on its own.

Manual wording: “6 RED FLASHES: This indicates that while the unit was operating, the pressure switch opened four times during the call for heat. Check for faulty inducer, blocked vent pipe or faulty pressure switch. The furnace will lock out for one hour and then restart.”

Documented for: TG8S, TG9S, TM9E, TM9X, TM8X, TM9T, TM8T, TM9V, TM8Y, TM9Y

Likely causes, most common first

  1. Faulty inducer (draft) motor
  2. Blocked vent pipe
  3. Faulty pressure switch

What you can safely check yourself

  • Check the outside vent and intake pipe terminations for snow, ice, leaves or nests
  • Check the condensate drain and trap for a clog
  • Replace a dirty air filter

When to call a technician

If the pipes are clear and the furnace keeps dropping out, the inducer or pressure switch is failing and needs a technician.

Sources

York furnace 7 Red Flashes: The burners failed to light on three trials for ignition, so the control locks out for one hour and then tries again

Soft lockoutShown as: Seven red flashes, then a two-second pause, repeating

The burners failed to light on three trials for ignition, so the control locks out for one hour and then tries again.

Manual wording: “7 RED FLASHES: This fault code indicates that the flame could not be established during three trials for ignition... The furnace will lock out for one hour and then restart.”

Documented for: TG8S, TG9S, TM9E, TM9X, TM8X, TM9T, TM8T, TM9V, TM8Y, TM9Y

Likely causes, most common first

  1. Gas valve switch left in the OFF position
  2. Low or no gas pressure
  3. Faulty gas valve
  4. Dirty or faulty flame sensor
  5. Faulty hot surface ignitor
  6. Loose wires or a burner problem

What you can safely check yourself

  • Check that other gas appliances in the house (stove, water heater) still work - if none do, the gas supply is out
  • Replace a dirty air filter
  • Check the outside vent and intake pipes for blockage
  • Cycle the furnace off and on once at the service switch to let it retry

When to call a technician

Anything past confirming you have gas to the house - ignitor, flame sensor, gas valve - is technician work in a live gas compartment.

Sources

York furnace 8 Red Flashes: The flame was lost five times

Soft lockoutShown as: Eight red flashes, then a two-second pause, repeating

The flame was lost five times (four recycles) during one heating cycle. The furnace locks out for one hour and then restarts.

Manual wording: “8 RED FLASHES: This fault is indicated if the flame is lost five times (four recycles) during the heating cycle. Check for low gas pressure, dirty or faulty flame sensor or faulty gas valve.”

Documented for: TG8S, TG9S, TM9E, TM9X, TM8X, TM9T, TM8T, TM9V, TM8Y, TM9Y

Likely causes, most common first

  1. Low gas pressure
  2. Dirty or faulty flame sensor
  3. Faulty gas valve

What you can safely check yourself

  • Check that other gas appliances in the house still work
  • Replace a dirty air filter
  • Check the outside vent and intake pipes for blockage

When to call a technician

Flame sensor cleaning and gas pressure checks are done with the burners running and require a manometer. Call a technician.

Sources

York furnace 9 Red Flashes: Reversed line voltage polarity, a grounding problem, or reversed low voltage transformer wires

Hard lockoutShown as: Nine red flashes, then a two-second pause, repeating

Reversed line voltage polarity, a grounding problem, or reversed low voltage transformer wires. The furnace will not start the ignition sequence until this is corrected, and both heating and cooling are affected.

Manual wording: “9 RED FLASHES: Indicates reversed line voltage polarity, grounding problem or reversed low voltage transformer wires. Both heating and cooling operations will be affected.”

Documented for: TG8S, TG9S, TM9E, TM9X, TM8X, TM9T, TM8T, TM9V, TM8Y, TM9Y

Likely causes, most common first

  1. Reversed line voltage polarity (hot and neutral swapped) at the furnace or at the branch circuit
  2. Poor or missing furnace ground
  3. Reversed low voltage transformer wires
  4. Flame probe shorted to the chassis

What you can safely check yourself

  • If this appeared right after electrical work or a new outlet/breaker was installed, mention that to the technician
  • Check the furnace breaker is fully on

When to call a technician

Polarity and grounding faults are line-voltage electrical work. Have a technician or electrician check the polarity and ground at the furnace and at the branch circuit.

Sources

York furnace 10 Red Flashes: The gas valve is energized with no call for heat

Safety faultShown as: Ten red flashes, then a two-second pause, repeating

The gas valve is energized with no call for heat. The main blower and inducer will run and no ignition sequence starts as long as the condition exists.

Manual wording: “10 RED FLASHES: Gas valve energized with no call for heat. The main blower and inducer blower will run and no ignition sequence will be started as long as this condition exists. Check gas valve and gas valve wiring.”

Documented for: TG8S, TG9S, TM9E, TM9X, TM8X, TM9T, TM8T, TM9V, TM8Y, TM9Y

Likely causes, most common first

  1. Faulty gas valve
  2. Gas valve wiring fault

What you can safely check yourself

  • If you smell gas, leave the house and call the gas utility from outside

When to call a technician

The gas valve is being powered when it should not be. Call a licensed technician immediately - do not keep operating the furnace.

Sources

York furnace 11 Red Flashes: The main limit switch opened and stayed open for more than five minutes, which the control reads as a failed blower

Hard lockoutShown as: Eleven red flashes, then a two-second pause, repeating

The main limit switch opened and stayed open for more than five minutes, which the control reads as a failed blower. It enters a hard lockout that only a power cycle clears.

Manual wording: “11 RED FLASHES: This indicates that the main limit switch has opened its normally-closed contacts and has remained open for more than five minutes. This condition is usually caused by a failed blower motor or blower wheel. The control will enter a hard lockout...”

Documented for: TG8S, TG9S, TM9E, TM9X, TM8X, TM9T, TM8T, TM9V, TM8Y, TM9Y

Likely causes, most common first

  1. Failed blower motor
  2. Failed or seized blower wheel

What you can safely check yourself

  • Check and replace the air filter
  • Open blocked supply registers and clear anything covering the return grille
  • Turn the furnace off at the service switch for a minute and back on once after the airflow problem is fixed

When to call a technician

A blower motor or wheel failure is a technician replacement job. If the code returns after one reset, stop resetting it and call for service.

Sources

York furnace 12 Red Flashes: The model ID plug on the control board is loose or missing

WarningShown as: Twelve red flashes, then a two-second pause, repeating

The model ID plug on the control board is loose or missing. The board uses this plug to know which furnace size it is running.

Manual wording: “12 RED FLASHES: This indicates a loose or missing model ID plug.”

Documented for: TM9V (2017 revision and later), and the modulating YP9C board (Twelve Red Flashes)

Likely causes, most common first

  1. Loose model ID plug
  2. Missing model ID plug

What you can safely check yourself

  • Turn the furnace off at the service switch for a minute and back on once

When to call a technician

Reseating the ID plug means opening the control compartment. Have a technician confirm the correct plug for the model is installed - the wrong plug makes the furnace fire at the wrong rate.

Source

York furnace 13 Red Flashes: The high-fire

WarningShown as: Thirteen red flashes, then a two-second pause, repeating

The high-fire (second stage) pressure switch is open when it should be closed. The furnace cannot run on high fire, so on the coldest days it may not keep up.

Manual wording: “13 RED FLASHES: This indicates that the high-fire pressure switch is open when it should be closed. Check for a partially blocked vent pipe or a loose or disconnected wire before replacing pressure switch.”

Documented for: TM9V, TM8V, TM8Y, TM9Y and other two-stage UPG furnaces

Likely causes, most common first

  1. Partially blocked vent pipe
  2. Loose or disconnected pressure switch wire
  3. Broken or disconnected pressure switch hose
  4. Faulty inducer
  5. Faulty second-stage pressure switch

What you can safely check yourself

  • Check the outside vent and intake pipe terminations for partial blockage from snow, ice, leaves or nests

When to call a technician

If the pipes are clear, the switch, hoses and inducer need to be tested with a manometer by a technician.

Sources

York furnace 4 Amber Flashes: The control is receiving a Y

WarningShown as: Four amber flashes, then a two-second pause, repeating

The control is receiving a Y (cooling) signal from the thermostat without a G (fan) signal. The furnace still heats and cools normally, but the wiring is wrong and the code is displayed to flag it.

Manual wording: “4 AMBER FLASHES: The control is receiving a "Y" signal from the thermostat without a "G" signal... Verify that the "G" wire from the thermostat is connected properly.”

Documented for: TG8S, TG9S, TM9E, TM9X, TM8X, TM9T, TM8T, TM9V, TM8Y, TM9Y

Likely causes, most common first

  1. The G wire from the thermostat is not connected properly

What you can safely check yourself

  • If a new thermostat was recently installed, mention it to the technician - the G (fan) wire is most likely off or on the wrong terminal

When to call a technician

Thermostat wiring corrections are quick for a technician. Left alone, the indoor blower may not run correctly during cooling.

Sources

York furnace 2 Green Flashes: There are no error codes stored in the control board's memory

StatusShown as: Two green flashes after pressing the LAST ERROR button

There are no error codes stored in the control board's memory. This is what the board answers when the LAST ERROR button is pressed and the fault history is empty.

Manual wording: “If there are no error codes in memory, the LED will flash two green flashes.”

Documented for: All UPG boards with a LAST ERROR button

Likely causes, most common first

  1. No stored faults in the control's five-code memory

When to call a technician

Not a fault. If the furnace is still misbehaving with no stored codes, a technician will need to watch it through a full cycle.

Sources

York furnace 3 Green Flashes: Confirmation that the stored error code memory has been cleared

StatusShown as: Three green flashes after holding the LAST ERROR button more than five seconds

Confirmation that the stored error code memory has been cleared. Not a fault.

Manual wording: “The LED will flash three green flashes when the memory has been cleared, then will resume the normal slow green flash after a five-second pause.”

Documented for: All UPG boards with a LAST ERROR button

Likely causes, most common first

  1. The LAST ERROR button was held for more than five seconds, clearing the fault history

When to call a technician

Not a fault. Clearing the fault history erases the evidence a technician uses to diagnose an intermittent problem, so leave the button alone before a service visit.

Sources

York furnace Steady Off (YP9C Modulating): No 24V power at the modulating control board

WarningShown as: No LED activity at all on the modulating control board

No 24V power at the modulating control board.

Manual wording: “STEADY OFF - No 24V power to board. Check the 24 volt control circuit fuse on the board. Check the circuit breaker or fuse on the 115 volt supply power to the furnace.”

Documented for: YP9C, YPLC modulating furnaces (and the identical TP9C / CP9C / LP9C chassis)

Likely causes, most common first

  1. Open 24 volt control circuit fuse on the board
  2. Tripped circuit breaker or blown fuse on the 115 volt supply
  3. Failed 24 volt transformer

What you can safely check yourself

  • Check the furnace breaker in the electrical panel is on
  • Check the furnace service switch is on
  • Make sure the lower door panel is fully seated

When to call a technician

If power at the breaker and switch is confirmed, the on-board fuse or the transformer has failed and needs a technician - a blown fuse usually means something else shorted.

Source

York furnace 1 Green Flash (YP9C Modulating): Normal operation with no call for heat

StatusShown as: One green flash, two-second pause, repeating

Normal operation with no call for heat. Standby.

Manual wording: “One Green Flash - Normal Operation with no call for heat.”

Documented for: YP9C, YPLC modulating furnaces

Likely causes, most common first

  1. Normal standby

What you can safely check yourself

  • If the house is cold, check the thermostat is set to HEAT and above room temperature

When to call a technician

No service needed.

Source

York furnace Rapid Green Flash (YP9C Modulating): The control is in Factory Speed-up mode, used only during factory run-testing

WarningShown as: Green LED flashing rapidly

The control is in Factory Speed-up mode, used only during factory run-testing. Cycling power to the furnace off and back on stops it.

Manual wording: “Rapid Green Flash - 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.”

Documented for: YP9C, YPLC modulating furnaces

Likely causes, most common first

  1. Control left in factory run-test (speed-up) mode

What you can safely check yourself

  • Turn the furnace off at the service switch for a minute, then back on once

When to call a technician

If a power cycle does not clear it, have a technician check the control board.

Source

York furnace 1 Amber Flash (YP9C Modulating): Normal operation with a call for cooling

StatusShown as: One amber flash, two-second pause, repeating

Normal operation with a call for cooling. Not a fault.

Manual wording: “One Amber Flash - Normal operation with call for cooling.”

Documented for: YP9C, YPLC modulating furnaces

Likely causes, most common first

  1. Normal air conditioning operation

When to call a technician

No service needed.

Source

York furnace 2 Amber Flashes (YP9C Modulating): Normal operation with a call for heat

StatusShown as: Two amber flashes, two-second pause, repeating

Normal operation with a call for heat. Not a fault.

Manual wording: “Two Amber Flashes - Normal operation with call for heat.”

Documented for: YP9C, YPLC modulating furnaces

Likely causes, most common first

  1. Normal heating operation

When to call a technician

No service needed.

Source

York furnace 3 Amber Flashes (YP9C Modulating): Normal operation - the burner is still on at the end of the heating cycle after the wall thermostat has been satisfied

StatusShown as: Three amber flashes, two-second pause, repeating

Normal operation - the burner is still on at the end of the heating cycle after the wall thermostat has been satisfied. Not a fault.

Manual wording: “Three Amber flashes - Normal operation, burner is on at end of heating cycle after wall thermostat has been satisfied.”

Documented for: YP9C, YPLC modulating furnaces

Likely causes, most common first

  1. Normal end-of-cycle burner operation on the modulating control

When to call a technician

No service needed.

Source

York furnace 4 Amber Flashes (YP9C Modulating): The furnace has automatically cut back its heating output because airflow through the house side is restricted

WarningShown as: Four amber flashes, two-second pause, repeating

The furnace has automatically cut back its heating output because airflow through the house side is restricted.

Manual wording: “Four Amber Flashes - Heating capacity is reduced due to restriction in the circulating air system. Check for dirty filter or closed registers.”

Documented for: YP9C, YPLC modulating furnaces

Likely causes, most common first

  1. Dirty air filter
  2. Closed or blocked supply registers

What you can safely check yourself

  • Check and replace the air filter
  • Open all supply registers and clear anything blocking the return grille

When to call a technician

If the code stays after a clean filter and open registers, the duct system or blower needs a technician.

Source

York furnace 5 Amber Flashes (YP9C Modulating): The furnace has cut back its heating output because the combustion air or vent system is restricted

WarningShown as: Five amber flashes, two-second pause, repeating

The furnace has cut back its heating output because the combustion air or vent system is restricted. Above 4,000 feet altitude this can also be normal automatic derating.

Manual wording: “Five Amber Flashes - Heating capacity is reduced due to restriction in the combustion air or vent system. Check for blocked vent/air pipe or clogged condensate drain.”

Documented for: YP9C, YPLC modulating furnaces

Likely causes, most common first

  1. Blocked vent or air intake pipe
  2. Clogged condensate drain
  3. Normal altitude derating above 4,000 feet

What you can safely check yourself

  • Check the outside vent and intake pipe terminations for snow, ice, leaves or nests
  • Check the condensate drain and trap for a clog

When to call a technician

If the pipes and drain are clear and you are not at high altitude, have a technician check the venting and inducer.

Source

York furnace 6 Amber Flashes (YP9C Modulating): Heat pump applications only: normal operation with a call for heat pump heating

StatusShown as: Six amber flashes, two-second pause, repeating

Heat pump applications only: normal operation with a call for heat pump heating. Not a fault.

Manual wording: “Six Amber Flashes - (Heat Pump applications only) Normal operation with call for heat pump heating.”

Documented for: YP9C, YPLC modulating furnaces paired with a heat pump

Likely causes, most common first

  1. Normal dual-fuel / heat pump heating operation

When to call a technician

No service needed.

Source

York furnace Rapid Amber Flash (YP9C Modulating): Low flame sense current

WarningShown as: Amber LED flashing rapidly

Low flame sense current. The control can barely detect the burner flame.

Manual wording: “Rapid Amber Flash - Low flame sense current. Check for dirty or mislocated flame sensor rod.”

Documented for: YP9C, YPLC modulating furnaces

Likely causes, most common first

  1. Dirty flame sensor rod
  2. Mislocated flame sensor rod

What you can safely check yourself

  • Replace a dirty air filter
  • Check the outside vent and intake pipes for blockage

When to call a technician

Cleaning or repositioning the flame sensor is done inside the live burner compartment. Call a technician before this turns into a no-heat lockout.

Source

York furnace 1 Red Flash (YP9C Modulating): Flame is present with no power being supplied to the gas valve - gas is reaching the burners when it should not be

Safety faultShown as: One red flash, two-second pause, repeating

Flame is present with no power being supplied to the gas valve - gas is reaching the burners when it should not be.

Manual wording: “One Red Flash - Flame is present with no power being supplied to gas valve. This can be caused by a gas valve that is slow to close or that leaks gas through to the burners.”

Documented for: YP9C, YPLC modulating furnaces

Likely causes, most common first

  1. Gas valve slow to close
  2. Gas valve leaking gas through to the burners

What you can safely check yourself

  • If you smell gas, leave the house and call the gas utility from outside

When to call a technician

Call a licensed technician right away. A leaking gas valve is a safety hazard and only a professional can test and replace it.

Source

York furnace 2 Red Flashes (YP9C Modulating): The pressure switch is closed while inducer pressure is below the switch setpoint - the switch is closed when it should be open, so the control will not start

Soft lockoutShown as: Two red flashes, two-second pause, repeating

The pressure switch is closed while inducer pressure is below the switch setpoint - the switch is closed when it should be open, so the control will not start.

Manual wording: “Two Red Flashes - Pressure switch closed with inducer pressure below pressure switch setpoint (switch is closed when it should be open). Check pressure switch and pressure transducer.”

Documented for: YP9C, YPLC modulating furnaces

Likely causes, most common first

  1. Faulty pressure switch stuck closed
  2. Faulty pressure transducer

What you can safely check yourself

  • Turn the furnace off at the service switch for a minute and back on once to see whether the code clears

When to call a technician

A stuck pressure switch is a safety interlock failure. It must be tested and replaced by a technician - never jumper it.

Source

York furnace 3 Red Flashes (YP9C Modulating): The pressure switch is open while inducer pressure is above the switch setpoint - the switch is open when it should be closed, so the burners cannot light

Soft lockoutShown as: Three red flashes, two-second pause, repeating

The pressure switch is open while inducer pressure is above the switch setpoint - the switch is open when it should be closed, so the burners cannot light.

Manual wording: “Three Red Flashes - Pressure switch open with inducer pressure above pressure switch setpoint (switch is open when it should be closed). Check pressure switch and pressure transducer.”

Documented for: YP9C, YPLC modulating furnaces

Likely causes, most common first

  1. Faulty pressure switch
  2. Faulty pressure transducer

What you can safely check yourself

  • Check the outside vent and intake pipe terminations for snow, ice, leaves or nests
  • Check the condensate drain and trap for a clog

When to call a technician

If the venting and drain are clear, the pressure switch or transducer needs a technician with a manometer.

Source

York furnace 4 Red Flashes (YP9C Modulating): High limit switch open, defective temperature sensor, or the 24 volt fuse is open

Soft lockoutShown as: Four red flashes, two-second pause, repeating

High limit switch open, defective temperature sensor, or the 24 volt fuse is open. Usually an airflow restriction is making the furnace overheat.

Manual wording: “Four Red Flashes - High limit switch open or defective temperature sensor or 24 volt fuse is open. This may be caused by a dirty air filter, improperly sized duct system, faulty blower motor, restricted circulating airflow an open fuse on the control board.”

Documented for: YP9C, YPLC modulating furnaces

Likely causes, most common first

  1. Dirty air filter
  2. Improperly sized duct system
  3. Faulty blower motor
  4. Restricted circulating airflow
  5. Open fuse on the control board

What you can safely check yourself

  • Check and replace the air filter
  • Open all supply registers and clear the return grille
  • Check that the furnace door panel is fully seated

When to call a technician

If the code returns with a clean filter and open vents, have a technician check the blower, ductwork and the board fuse. Never bypass the limit switch.

Source

York furnace 5 Red Flashes (YP9C Modulating): The rollout switch or the condensate pressure switch is open

Safety faultShown as: Five red flashes, two-second pause, repeating

The rollout switch or the condensate pressure switch is open. A rollout trip means flame or hot gas escaped the burner compartment; a condensate switch trip means the drain has backed up.

Manual wording: “Five Red Flashes - Rollout switch or condensate pressure switch open. Check the rollout switch(es) on the burner assembly. It is a manual reset switch... If it cannot be reset or if the switch trips again, contact a qualified serviceman.”

Documented for: YP9C, YPLC modulating furnaces

Likely causes, most common first

  1. Flame rollout switch tripped on the burner assembly
  2. Condensate pressure switch open from a backed-up drain

What you can safely check yourself

  • Check the condensate drain line and trap for a clog and clear standing water from the drain pan area
  • Check the outside vent and intake pipes for blockage
  • If you smell exhaust fumes or a CO alarm sounds, leave the house and call for service from outside

When to call a technician

The manual is explicit: if the rollout switch cannot be reset or trips again, contact a qualified serviceman. A repeat rollout can mean a cracked heat exchanger and a carbon monoxide risk - do not keep resetting it.

Source

York furnace 6 Red Flashes (YP9C Modulating): Gas valve communication error

Soft lockoutShown as: Six red flashes, two-second pause, repeating

Gas valve communication error. The modulating gas valve and the control board have lost their data link, so the furnace cannot modulate or fire.

Manual wording: “Six Red Flashes - Gas valve communication error.”

Documented for: YP9C, YPLC modulating furnaces

Likely causes, most common first

  1. Loss of communication between the control board and the modulating gas valve

What you can safely check yourself

  • Turn the furnace off at the service switch for a minute and back on once

When to call a technician

Modulating gas valve communication faults are a technician job - the valve, its harness and the board all have to be checked.

Source

York furnace 7 Red Flashes (YP9C Modulating): Lockout due to no ignition

Soft lockoutShown as: Seven red flashes, two-second pause, repeating

Lockout due to no ignition. The control tried three times to light the burners and failed, so it locks out for one hour and then tries again.

Manual wording: “Seven Red Flashes - Lockout due to no ignition. The control will try three times for ignition. If flame cannot be established in three tries, the control will lockout for one hour and then will try again to light.”

Documented for: YP9C, YPLC modulating furnaces

Likely causes, most common first

  1. No or low gas supply
  2. Failed hot surface ignitor
  3. Faulty gas valve
  4. Dirty or faulty flame sensor

What you can safely check yourself

  • Check that other gas appliances in the house still work
  • Replace a dirty air filter
  • Check the outside vent and intake pipes for blockage
  • Cycle the furnace off and on once at the service switch to let it retry

When to call a technician

Ignitor, flame sensor and gas valve work all happen inside the live gas compartment. Call a technician.

Source

York furnace 8 Red Flashes (YP9C Modulating): Lockout due to too many flame recycles - the flame was lost five times during a single heating cycle

Soft lockoutShown as: Eight red flashes, two-second pause, repeating

Lockout due to too many flame recycles - the flame was lost five times during a single heating cycle. The control locks out for one hour, then tries again.

Manual wording: “Eight Red Flashes - Lockout due to too many flame recycles. This flash code occurs if flame is lost five times during a single heating cycle.”

Documented for: YP9C, YPLC modulating furnaces

Likely causes, most common first

  1. Faulty gas valve
  2. Low gas pressure
  3. Dirty flame sensor

What you can safely check yourself

  • Check that other gas appliances in the house still work
  • Replace a dirty air filter

When to call a technician

Gas pressure and flame sensor checks require a manometer and live-burner access. Call a technician.

Source

York furnace 9 Red Flashes (YP9C Modulating): Reversed line polarity or improper grounding at the furnace

Hard lockoutShown as: Nine red flashes, two-second pause, repeating

Reversed line polarity or improper grounding at the furnace.

Manual wording: “Nine Red Flashes - Reversed line polarity or improper grounding. Check polarity of the incoming power to the furnace. Check the grounding of the furnace, including the transformer ground and the L1 and neutral connections.”

Documented for: YP9C, YPLC modulating furnaces

Likely causes, most common first

  1. Line voltage hot and neutral reversed
  2. Poor or missing furnace ground
  3. Bad transformer ground or L1/neutral connection

What you can safely check yourself

  • If this appeared right after electrical work, mention that to the technician
  • Check the furnace breaker is fully on

When to call a technician

Polarity and grounding are line-voltage electrical work. Have a technician or electrician correct it.

Source

York furnace 10 Red Flashes (YP9C Modulating): Gas valve circuit shorted

Safety faultShown as: Ten red flashes, two-second pause, repeating

Gas valve circuit shorted.

Manual wording: “Ten Red Flashes - Gas valve circuit shorted. Check gas valve wiring. If correct, replace gas valve.”

Documented for: YP9C, YPLC modulating furnaces

Likely causes, most common first

  1. Shorted gas valve wiring
  2. Failed gas valve

What you can safely check yourself

  • If you smell gas, leave the house and call the gas utility from outside

When to call a technician

A shorted gas valve circuit is a gas-safety fault. Call a licensed technician and do not keep cycling the furnace.

Source

York furnace 11 Red Flashes (YP9C Modulating): Main blower failure

Hard lockoutShown as: Eleven red flashes, two-second pause, repeating

Main blower failure. The main limit opened and did not reclose within five minutes, which the control reads as a failed blower motor or blower wheel.

Manual wording: “Eleven Red Flashes - Main blower failure - This flash code occurs when the main limit opens and fails to reclose within five minutes, indicating that the blower motor or blower wheel has failed.”

Documented for: YP9C, YPLC modulating furnaces

Likely causes, most common first

  1. Failed blower motor
  2. Failed blower wheel

What you can safely check yourself

  • Check and replace the air filter
  • Open blocked supply registers and clear the return grille

When to call a technician

Blower motor or wheel replacement is a technician job. Stop resetting the furnace if the code returns.

Source

York furnace 12 Red Flashes (YP9C Modulating): The model ID plug is not present or not connected properly

WarningShown as: Twelve red flashes, two-second pause, repeating

The model ID plug is not present or not connected properly.

Manual wording: “Twelve Red Flashes - ID plug is not present or not connected properly, check for loose plug or loose wires in plug.”

Documented for: YP9C, YPLC modulating furnaces

Likely causes, most common first

  1. Loose ID plug
  2. Loose wires in the ID plug
  3. Missing ID plug

What you can safely check yourself

  • Turn the furnace off at the service switch for a minute and back on once

When to call a technician

Have a technician confirm the correct ID plug is fitted and seated - the wrong plug makes the furnace fire at the wrong rate.

Source

York furnace Steady On Red (YP9C Modulating): A control fault has been detected, or 115 volts is present without 24 volts

Hard lockoutShown as: Red LED lit solid, not flashing

A control fault has been detected, or 115 volts is present without 24 volts.

Manual wording: “Steady On Red - Control fault has been detected or there is 115 volts present without 24 volts... If there is both 24 and 115 voltage to the board, replace the control board.”

Documented for: YP9C, YPLC modulating furnaces

Likely causes, most common first

  1. Missing 24 volt supply to the board (blown control fuse or failed transformer)
  2. Failed control board

What you can safely check yourself

  • Turn the furnace off at the service switch for a minute, then back on once

When to call a technician

If both 24V and 115V are present and the LED is still solid red, the board has to be replaced. Voltage checks and board replacement are technician work.

Source

York furnace 2 Green Flashes (YP9C Modulating): Indicator for 'No error codes in memory'

StatusShown as: Two green flashes after pressing the LAST ERROR button

Indicator for 'No error codes in memory'. Not a fault.

Manual wording: “Two Green Flashes - Indicator for "No error codes in memory".”

Documented for: YP9C, YPLC modulating furnaces

Likely causes, most common first

  1. No stored faults in the control's five-code memory

When to call a technician

Not a fault. Johnson Controls states only a qualified service technician should use the fault-history feature.

Source

York furnace 3 Green Flashes (YP9C Modulating): Indicator for 'Error codes cleared from memory'

StatusShown as: Three green flashes after holding the LAST ERROR button more than five seconds

Indicator for 'Error codes cleared from memory'. Not a fault.

Manual wording: “Three Green Flashes - Indicator for "Error codes cleared from memory".”

Documented for: YP9C, YPLC modulating furnaces

Likely causes, most common first

  1. The stored fault history was cleared with the LAST ERROR button

When to call a technician

Not a fault, but clearing the history erases what a technician needs to chase an intermittent problem - leave it alone before a service visit.

Source

How old is this York?

Age changes what a fault code means for you. The same failure is a routine repair on a six-year-old unit and the end of the line on a twenty-year-old one. Your York serial number has the build date in it.

Decode your Yorkserial number →

Manuals used for this page