12 Trane Furnace Error Codes – Essential Guide

If you have ever experienced an issue with Trane furnace error codes, you may have been left scratching your head. Well, those flashing LEDs mean something!

In this guide, you’ll find out what all these codes mean and what exactly you should do to try and fix the problem.

How to Enter Service Mode on a Trane Furnace?

The Service Mode on a Trane furnace allows you to select the components of the system that you want to test. The unit will selectively turn the dampers, heaters, compressor, etc. on and off and then perform a service test to find out if everything is okay.

Simply press the key that says ‘Service Mode’ to enter the menu. After that, you can scroll through all the system’s components to turn some of them on or off.

Do bear in mind that the service mode screen will automatically revert back to the general display if no key had been pressed for over 30 minutes.

Read: American Standard Furnace – Troubleshooting Guide

How to Enter the Status Menu on Trane Furnace?

You can enter the Status Menu to view the unit’s components status, temperature and humidity levels, and different setpoints.

To enter the menu, press the Status key. You can press the ‘+’ to add a certain screen to your custom menu (this will save you quite some time in the future, as you wouldn’t have to go through all of the system’s components, in order to find what you’re looking for).

Just like with the Service Mode, the device will return to its regular display, if no one presses the keys for 30 minutes.

Trane Furnace Error Codes

1. A Slowly Flashing Light

The system is operating properly; no call for heat.

A slowly flashing light is technically one of your Trane furnace error codes, but it’s not really indicating an error at all. Everything is fine, and it’s simply waiting for a signal from the thermostat to start operating.

Have a Question? Ask HVAC Technician

Click here to use the chatbox to speak with one of our technicians.
No in-home service calls. No appointments.

However, if you have already raised the temperature, but the furnace is irresponsive, then such a slowly flashing light can become a problem. 

When a furnace is not responding to the thermostat, these are a few things that you can do:

  • Change your air filter

One of the most common issues for any furnace-related problem is simply a clogged air filter. If the airflow is restricted, the exchanger might overheat and shut the whole system down.

Read: Why Does My Furnace Filter Get Dirty So Quickly?

Also: Which Side Of The Air Filter Faces Out?

The device has to be set to ‘heat’, it should be properly attached to the wall and you shouldn’t be able to see any loose or frayed wires. 

Also, make sure that the time and date are correct and that the batteries have not died.

Read: Why Does Home Thermostat Say HEAT ON But There Is No Heat?

  • Check the electrical components

Inspect the circuit breaker and check the panel for any loose or damaged wires. By the way, the fuse might be tripped or blown, so do check that as well.

2. A Rapidly Flashing Light

The system is operating properly; call for heat.

This means that your unit is on and that it’s giving a call for heat, so everything should be fine.

However, if the furnace is calling for heat all the time, this might indicate that the unit is not responding to the thermostat (follow the instructions mentioned above). 

3. Continuous On

There is an issue with the control panel.

If the furnace light stays on, no matter what you do, then there is a problem with the control panel and you will, most likely, have to replace it.

It is quite challenging for a homeowner to figure out by himself, if the control board had actually gone bad or not – to solve such a riddle, you would have to know exactly how the system is attached to works.

Here are the things that can cause your control panel to go bad:

  • Loose wiring

After some time, the wires in the system might get loose because of the furnace’s vibration. Moreover, the wires can simply corrode or get damaged over time.

  • Clogged filters

Restricted airflow can make the blower motor overheat.

  • Dirty or wrong fuse
Fuse board

A fuse might be too small for your system or simply dirty. This, in its turn, will cause the control board to break down.

4. Continuous Off

The power is off.

Here, you would have to check your power source. Hopefully, the issue is with the power and not the actual unit.

To find out whether or not your furnace is getting electricity, throw the thermostat’s fan switch to ‘on’. If the fan starts working, then your unit is receiving electricity. 

In case that didn’t help, locate the breaker panel and the circuit that controls the panel. The circuit breaker might have tripped, in such a case, the switch would be either in the ‘off’ or the middle position.

Another thing that you can do is check the furnace switch that is usually located on the unit or on the wall right next to the furnace. The switch should be in the ‘on’ position.

Tip: if you had to change the position of any of the switches, make sure to give the furnace at least a few minutes as some units get switched on with a delay. 

Now, we’ll get into the flash patterns of the various Trane furnace error codes.

5. 2 Flashes

There has been a lockout.

If you can check for miswiring.

Your unit might also have a clogged pilot tube. To clean the components, get a needle and carefully scrape the inside of the tube.

Another possible issue that caused the system to lock out is humidity in the unit.

It is absolutely normal for high-efficiency furnaces to produce condensation during the operation process, but the system should also be able to get rid of the excess moisture.

If the unit fails to successfully do that, the condensate drains might be blocked, or there may be problems with the condensate pump, or there are issues with the condensation line. 

Trane furnace error codes circuit board

6. 3 Flashes

A pressure switch error. 

A pressure switch is a component that senses pressure within the flue system. It is a safety mechanism that helps protect the system from overheating.

Here are some steps that you can follow to fix the problem:

  1. Locate and then remove the front access panel.
  2. Unplug the 24-volt wires from the switch (if you don’t feel comfortable working with wires, leave this to a professional).
  3. Connect an ohmmeter to the switch. Check the pressure switch terminals as soon as the fan begins to run. The readings should be close to zero, if they are not, then the actual pressure switch needs to be replaced.
  4. If the switch is okay, then turn the unit off and let it cool for at least 30 minutes.
  5. Test the inducer fan – simply try spinning it manually. If the component spins freely, then proceed to the next step.
  6. Inspect the venting pipes. Leaves, nests, and debris might be clogging them.
  7. Remove the obstructions and check if the flashes had gone away.

Read: Why Gas Furnace Is Overheating?

7. 4 Flashes

There is an open temperature limit circuit issue (or an open high limit switch).

Make sure that the flame sensor rod on the switch is not dirty.

8. 5 Flashes

The unit sensed a flame when no flame should be present.

Check the flame sensor and the gas valves. The latter might be stuck or leaking gas.

Read: How Long Do Flame Sensors Last?

9. 6 Flashes 

A reversed polarity issue or poor grounding.

If you know how to work with wires, you can check the connections. Verify that the polarity at the furnace is correct (the neutral wire should not be connected to where the hot wire should be). 

furnace control panel

10. 7 Flashes

There is a gas valve circuit error.

You would have to check the gas valves. Ensure that they are not leaking any gas and that the valves are not stuck.

How do you know if your gas valve is leaking?

Tip: always start your inspection from the pipes that go towards the furnace and end with the pilot tube and burners.

You can use a carbon monoxide detector, a special gas detector, or a soap spray (dump the solution on the fittings to ensure that no bubbles get formed). 

Read: Why Furnace Is Running But Not Blowing Air?

11. 8 Flashes

There is a low flame.

This might be because of low gas pressure or an issue with the flame sensor. You can try removing the sensor and cleaning the component with very light grit sandpaper.  

12. 9 Flashes

Check your ignitor.

Make sure that the furnace is receiving power, inspect the connections and the circuit board.

Usually, the actual furnace has a longer lifespan than the ignitor. So, perhaps, the time has come to change the component. 

Final Thoughts

Now that we’ve covered the Trane furnace error codes, hopefully the next time your furnace starts blinking at you, you will know just how to approach the issue. But remember that not every time it flashes necessarily mean there’s a problem. Check back with our list any time to be sure.

Related: Goodman, Lennox, Carrier, Rheem, & Bryant Furnace Error Codes