Trane E12 Error Code – 4 Causes & Solutions!

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In the heating and air conditioning industry, Trane is a popular brand. They are well known for their furnaces. But no system is free from faults. So, they can occasionally face problems as well.

But what is indicated by the Trane E12 error code?

Usually, this E12 error code indicates the combustion motor error or ignition circuit problem. Defective thermocouples are the most common cause of this error. However, a fault in the pilot assembly can also show this code. When this assembly doesn’t work properly, the E12 error code appears to you.

The above portion only gives a basic idea of the error code. But there’s a broader concept of the problem. And for that, you’ll have to go through the full article below. 

So, please keep reading along to know more.

What is the E12 Error Code?

Electrical components are bound to malfunction after using for a certain amount of time. That’s why manufacturers always include common problems and fixes in the user manual.

Very often, these common problems are indicated by some equipment error codes. This code helps to quickly identify the actual cause and fix it accordingly. Trane also does the same.

E12 error code is also one of the provided codes. And it’s related to the combustion motor which is an integral part of the furnace. It helps to heat or cool and in air conditioning. The ignition circuit creates the spark for the combustion motor to work.

Error code E12 can also occur due to pilot assembly errors.

Reasons for E12 Error

There are some common reasons which lead to the E12 error code of Trane furnaces. And here they go-

1. Disconnection of Heating Coil

If the heating coil is turned off or disconnected, this problem may occur. Heating coils convert electricity into heat. When this coil doesn’t work, the combustion can’t take place.

As a result, the combustion motor fails and error code E12 appears. So, this is one of the reasons behind the error code E12 issue.

Connecting the heating coil again can solve this issue.

2. Gas Valve Issue or Combustion Blower Issue

The gas valve maintains the gas flow pressure on the furnace. If this function is hampered, the gas pressure becomes unstable. And the gas valve doesn’t work properly.

Following that, the combustion blower also fails to do its work. This total thing is a significant reason for the E12 error code. Because this eventually leads to combustion motor error.

So, check the gas valve and adjust it accordingly.

3. Heat Exchanger Wiring Issue

Wiring issues are very common in electrical appliances. Very often the wires are loosened or get disconnected. This can happen with your Trane furnace as well.

Heat Exchanger Wiring Issue

Sometimes the wiring connection is damaged in your Trane furnace heat exchanger. Due to this, the heat exchanger doesn’t work properly. The transition of heat is not possible and thus the combustion is hampered.

For this reason, this is a potential reason for the E12 error code.

4. Incorrect Setting of Thermostat

A thermostat works by regulating the heating and cooling operation. When the thermostat is not set correctly, it does not record the correct temperature. Then it fails to regulate the heating and cooling operation.

Eventually, the combustion system is hampered and the combustion motor doesn’t work. And we know that the failure of the combustion system is the E12 error code. That’s why the incorrect setting of the thermostat also causes the E12 error. 

So, these were the reasons for the E12 error code. Knowing these reasons can help you to fix the problem.

How to Fix of The Problem Trane E12 Error Code?

It’s pretty annoying when the Trane furnace doesn’t seem to work. But as you’ve identified the cause, the fixation can be done now. And you can reset the Trane error codes as well. 

We’ve listed down some possible troubleshooting ideas for you. Please have a look.

1. Checking The Connections

Check all the connections before turning on the furnace. Check if the heating coil is turned on. Turn it on if needed and connect it when necessary.

Also, it takes time for the furnace to heat up your room. Set the thermostat to the correct temperature.

2. Fixing The Wirings

Loose wiring connections won’t let the furnace work. So, check the wirings and connect them properly. See if the wires have worn out. In that case, change the wirings if necessary. Also, use good quality wires for the connections.

If you’re looking for excellent quality wirings with utmost safety, check the ones below.

  • Trane WIR05025 Central wire harness– OEM branching harness, It’s in American Standard.
  • Trane Air Conditioning Communication Cable– You can find a cluster of Trane wires here.

These wires will surely serve you for a long time with a good connection. For your convenience, here’s a diagram of Trane wiring.

3. Claiming Warranty

Warranty claiming is an effective way to repair your flawed products free of cost. But usually, there are some conditions set by the manufacturer to avail of the warranty.

Generally, a 1-year warranty is provided by Trane. In this timeframe, they will repair your furnace free of cost under certain circumstances. So, if you find any manufacturing defect on the furnace, contact them for warranty services.

4. Calling Out Professionals

If you’re out of warranty, this is the way to go. If you’re not acquainted with the furnace system, take help from professional repair services.

There are a lot of service providers out there. You can hire one who will do your work. But try to hire those who have experience in this field. However, this will cost you money.

So, these are some ways for you to solve the E12 error code issue. Use the one according to your convenience. And don’t forget to ground the furnace before doing any work on them.

Frequently Asked Questions (FAQs)

Now we’ll be discussing some of the most commonly asked questions regarding this.

How to clear a Trane error code?

You can clear a Trane error code simply by resetting the circuit breaker. After you reset the furnace, wait for a moment before restarting it. Thus you can successfully clear the Trane error code.

How is it possible to reset the Trane furnace?

Turn off the furnace from the power connection to reset the Trane furnace. After that, reach out to the control panel. There you will find a reset button beside the blower motor on the blower compartment. Press the reset button to reset the furnace.

What’s the reason for the furnace not turning on?

Furnace not turning on can occur due to dirty air filters. Dirty air filters don’t let the air flow properly and prevent the furnace from starting. So, clean the air filters regularly. Also, check the thermostat settings, gas line switch, etc.

How much time does it take to reset the furnace?

After pressing the reset button, it takes around 30 seconds for the furnace to reset. Make sure to hold the reset button for 30 seconds after you press it. Also, set the thermostat to the desired temperature.


Hope you have no confusion left about the Trane E12 error code. We tried to cover all the aspects to clear out your queries.

Although Trane is a trusted brand, problems occurring are normal. So, don’t get panicked and follow the proper procedure to fix the problem. 

That’s all for this time. Have a good day.

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