Gas Furnace Error Codes: What They Mean and What to Do

Gas furnace burners lit with blue flames beneath the gas valve

Gas Furnace Error Codes: What They Mean and What to Do

Modern gas furnaces diagnose themselves. When something goes wrong, the control board shuts the furnace down and reports why, usually with a blinking light visible through a small window in the lower door, or a code on a small digital display. That code is genuinely useful. It tells you which part of the system tripped, whether it is something you can safely check, and whether you should stop and call.

This guide covers the codes used by the brands we service most often in Vancouver and Portland homes. Read the safety section first. It is the most important part of this page.

Safety First: Read This Before Anything Else

If you smell gas, ignore the code entirely. Do not reset the furnace, do not flip light switches, and do not use your phone inside. Leave the house and call your gas utility or 911 from outside.
If a carbon monoxide alarm is sounding, get everyone outside and call 911. Do not stay to read the furnace display.
Never reset a flame rollout code. A rollout switch trips when flames come out of the combustion chamber where they do not belong, usually from a blocked flue or a cracked heat exchanger. Resetting it and letting the furnace run again is how furnace fires and carbon monoxide exposure happen.
Never reset a code that says flame is present when the furnace is not calling for heat. That can mean gas is flowing when the valve should be closed. Turn the furnace off at its service switch and call for service.
Reset once, not repeatedly. For codes that are safe to reset, turn the furnace off at its service switch for 30 seconds and turn it back on. If the same code comes back, stop. Resetting a furnace over and over hides a real problem and can make it worse.
Never bypass or jumper a safety switch. Pressure switches, limit switches, and rollout switches exist to shut the furnace down before something dangerous happens.
Do not open the burner compartment or touch the gas valve. Burners, igniters, flame sensors, and gas valves are technician work.

How to Read Your Furnace Code

Most furnaces have a small sight glass in the lower door where you can see a status light without removing any panels. Watch it for a full minute and count carefully. Most codes repeat with a longer pause between each round.

Single light, counted flashes. Goodman, Amana, Trane, American Standard, Rheem, Ruud, and many York models. Count the flashes between pauses. Two flashes, pause, two flashes means code 2.
Two digit flash codes. Carrier, Bryant, and Payne. A set of short flashes gives the first digit, a pause, then a set of longer flashes gives the second. Three short, pause, four long is code 34.
Digital display codes. Many newer Lennox furnaces show a code such as E223 on a small screen, and communicating thermostats often display the same code.

One important caution: codes vary between models and control boards, even within the same brand. The chart printed on the inside of your furnace door, or in your owner's manual, is the final word for your specific unit. Use the lists below as a guide, and trust the label on your furnace if they disagree.

What the Codes Mean, by Problem

Nearly every brand's code list comes down to the same handful of problems. Understanding these makes any code easier to act on.

Ignition Failure or Lockout

The furnace tried to light several times and never confirmed a flame, so it locked itself out. Most furnaces retry on their own after one to three hours.

Safe to check: the thermostat is set to heat and set above room temperature, the furnace service switch is on, and the breaker has not tripped. If the gas utility recently shut off service or you have other gas appliances not working, call the utility. Reset once.

Call a technician if: the code returns. Common causes are a dirty flame sensor, a failing igniter, or a gas supply problem, and all of them involve the burner compartment.

Pressure Switch Codes

Before the burners light, a small inducer fan pushes exhaust out through the vent pipe, and a pressure switch confirms the vent is clear. A pressure switch code means the furnace could not confirm safe venting, or the switch is stuck.

Safe to check: on high-efficiency furnaces with white plastic vent pipes, look at where the pipes exit the house. Snow, ice, leaves, wasp nests, and bird nests all block them. Clear anything you can reach safely from outside by hand. Also look for a visibly kinked or disconnected rubber hose or a condensate drain line that is backed up with water. Reset once.

Call a technician if: the vents are clear and the code returns. A blocked vent you cannot see, a failed inducer motor, a clogged condensate trap, or a bad switch all need hands-on diagnosis.

High Limit Codes

The furnace got too hot and shut the burners off. The number one cause is restricted airflow.

Safe to check: replace the air filter, especially if you recently switched to a thicker or higher rated filter. Open any closed supply vents and clear furniture or rugs off return grilles. Reset once.

Call a technician if: the code returns with a clean filter and open vents. A failing blower motor, a dirty blower wheel, or undersized ductwork can cause it, and repeated overheating stresses the heat exchanger.

Flame Rollout Codes

Do not reset. Turn the furnace off at its service switch and call for service. Rollout means flame escaped the combustion area. Causes include a blocked flue, a cracked heat exchanger, or incorrect gas pressure, and some of these can put carbon monoxide into your home. Make sure your carbon monoxide detectors are working while you wait.

Flame Sensed Out of Sequence

Do not reset. The furnace sees a flame when the gas valve should be closed. The cause may be a sensor fault, but it can also be a gas valve that is not shutting off fully. Turn the furnace off at its service switch and call. If you smell gas at any point, leave the house and call your gas utility from outside.

Low Flame Signal

The furnace lights but the flame sensor reading is weak, so it may shut down shortly after lighting. The usual cause is a dirty or oxidized flame sensor. This is a quick service item, but it requires opening the burner compartment, so it belongs to a technician.

Igniter Circuit Codes

The hot surface igniter or its wiring has failed. Igniters are fragile and wear out with age. A reset will not fix it, and the replacement should be done by a technician.

Reversed Polarity or Grounding Codes

The furnace is detecting a wiring problem in its power supply, often after electrical work, a new outlet, or a furnace replacement. This is an electrical issue. Call a technician rather than opening the furnace's wiring.

Blower or Inducer Motor Codes

One of the furnace's motors is not running correctly. Check the filter first, since restricted airflow can make a blower struggle. Beyond that, motor diagnosis and replacement is technician work.

Error Codes by Brand

These are the most commonly documented codes. Remember to confirm against the chart on your own furnace door.

Carrier, Bryant, and Payne

11: No previous code stored. Normal.
12: Blower running after power-up. Usually normal after a power interruption.
13: Limit circuit lockout. The high limit or rollout switch stayed open too long. If the cause was rollout, do not reset.
14: Ignition lockout. The furnace failed to light after several tries.
21: Gas heating lockout. Call a technician.
22: Abnormal flame proving signal. Flame sensed when the gas valve should be off. Do not reset.
23: Pressure switch did not open.
24: Secondary voltage fuse open. Often a wiring short. Call a technician.
31: Pressure switch did not close, or reopened. Check exterior vent pipes and the condensate drain.
33: Limit circuit fault. The high limit or rollout switch is open. Check the filter first, and do not keep resetting.
34: Ignition proving failure. Often a dirty flame sensor or weak igniter.
41: Blower motor fault.
45: Control circuitry fault. The control board needs attention.

Lennox

E200: Flame rollout circuit open. Do not reset.
E207: Hot surface igniter open.
E223: Low pressure switch failed to close. Check exterior vent pipes and condensate drain.
E225: High pressure switch failed to close.
E240: Low flame current while running. Often a dirty flame sensor.
E241: Flame sensed out of sequence. Do not reset.
E250: Limit switch circuit open. Check the filter and vents.
E270: Lockout after too many failed ignition attempts.
E273: Flame lost repeatedly while running.
E274: Limit switch open for more than three minutes.
E290: Igniter circuit fault.
E291: Heating airflow below minimum. Check the filter and return grilles.
E294: Combustion air inducer motor overcurrent.

Goodman and Amana

Steady light: Normal, or no call for heat.
1 flash: Lockout after repeated ignition failures.
2 flashes: Pressure switch stuck closed, or an inducer problem.
3 flashes: Pressure switch did not close. Check exterior vent pipes and the condensate drain.
4 flashes: Primary limit circuit open. Check the filter first.
5 flashes: Flame sensed with no call for heat. Do not reset.
7 flashes: Low flame sense signal.
8 flashes: Igniter circuit problem.
9 flashes: High-stage pressure switch did not close on two-stage furnaces.
Continuous rapid flashing: Reversed power polarity.

Trane and American Standard

Slow flash: Normal, no call for heat.
Fast flash: Normal, calling for heat.
Steady on: Control board fault.
2 flashes: System lockout. No flame established.
3 flashes: Pressure switch fault. Check exterior vent pipes and the condensate drain.
4 flashes: High limit open. Check the filter first.
5 flashes: Flame sensed with the gas valve off. Do not reset.
6 flashes: Reversed polarity or poor grounding.
7 flashes: Gas valve circuit error. Call a technician.
8 flashes: Low flame sense signal.
9 flashes: Igniter circuit problem.

Rheem and Ruud

Steady status light: Normal operation.
1 flash: Ignition failure. The furnace is locked out for about an hour.
2 flashes: Pressure switch stuck open. Check exterior vent pipes and the condensate drain.
3 flashes: Limit switch open, which can include flame rollout. Do not keep resetting.
4 flashes: Pressure switch stuck closed.
6 flashes: Line and neutral reversed.

York, Luxaire, and Coleman

These codes apply to many newer furnaces with red status light codes. Older models vary, so check your door chart carefully.

Slow green flash: Normal, no call for heat.
Slow amber flash: Normal, calling for heat.
Rapid amber flash: Low flame sense signal.
1 red flash: Flame sensed with no call for heat. Do not reset.
2 red flashes: Pressure switch stuck closed.
3 red flashes: Pressure switch did not close. Check exterior vent pipes and the condensate drain.
4 red flashes: Limit switch open. Check the filter first.
5 red flashes: Rollout switch open. Do not reset.
7 red flashes: Lockout. No flame after repeated ignition attempts.
9 red flashes: Reversed polarity or grounding problem.
10 red flashes: Gas valve energized with no call for heat. Turn the furnace off and call.

What to Have Ready When You Call

A few details help a technician arrive prepared and often shorten the visit:

The brand and the exact code, including light color or flash count
The model and serial number from the label inside the furnace door
When the problem started, and whether you reset the furnace
Anything that changed recently, such as a new filter, snowfall, electrical work, or a power outage
Whether any carbon monoxide detector has sounded or you have noticed any unusual smell

The Short Version

Gas smell or carbon monoxide alarm: leave the house first, then call from outside
Rollout and flame out of sequence codes: do not reset, turn the furnace off and call
Pressure switch codes: check exterior vent pipes for snow, ice, or nests
High limit codes: replace the filter and open vents
Reset once at most, and never bypass a safety switch
The chart inside your furnace door is the final word for your model

Need Help With a Furnace Error Code?

Error codes point toward a problem, but diagnosing and repairing a gas furnace safely takes a trained specialist. If your furnace is showing a code that keeps coming back, a rollout or gas valve code, or anything you are not comfortable checking, HVA Climate Control can help. Our technicians service gas furnaces throughout Vancouver WA and the Portland metro area.

Call us at (360) 888-2217 or use the contact form on our website to schedule an appointment with a furnace specialist. Tell us the code you are seeing and we will make sure the right technician arrives prepared.