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A Trane thermostat image illustrating how to read and fix Trane XL90 error codes

How to Read and Fix Trane XL90 Error Codes: A Complete Guide

To read and fix Trane XL90 error codes, locate the LED indicator on the furnace control board, match the number of flashes to the corresponding error code in the documentation,…

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To read and fix Trane XL90 error codes, locate the LED indicator on the furnace control board, match the number of flashes to the corresponding error code in the documentation, and follow the troubleshooting steps provided to address the specific issue.

When it comes to reliable and efficient heating for your home, the Trane XL90 furnace stands as a trusted option. Equipped with advanced features and built to deliver optimal performance, the Trane XL90 furnace ensures your comfort during cold winter months. 

However, like any complex system, occasional issues may arise. That’s where understanding Trane XL90 error codes becomes valuable.

What are Trane XL90 Error Codes?

Trane XL90 furnaces are equipped with a diagnostic system that utilizes error codes to identify and communicate specific issues or malfunctions. When a problem occurs within the furnace, it generates an error code, providing valuable information to homeowners and HVAC technicians. 

These codes act as a guide, helping you troubleshoot and fix common problems with your Trane XL90 furnace.

By being familiar with Trane XL90 error codes, you gain insights into potential issues and can take appropriate actions to resolve them promptly. Let’s explore the benefits and importance of understanding these error codes:

How to Read Trane XL90 Error Codes

Reading Trane XL90 error codes is a straightforward process that can help you pinpoint specific issues with your furnace. The LED indicator on the furnace control board provides valuable information through a series of flashes. 

Follow these steps to interpret Trane XL90 error codes:

  1. Locate the Furnace Control Board: The furnace control board is typically located inside the furnace cabinet. You may need to remove the access panel to access the control board.
  1. Identify the LED Indicator: Look for the LED indicator light on the furnace control board. It is designed to flash a specific number of times to indicate different error codes.
  1. Count the Number of Flashes: Observe the LED indicator closely and count the number of flashes it emits in a sequence. Each flash represents a numerical value that corresponds to a specific error code.
  1. Refer to the Error Code Table: Once you have counted the flashes, refer to the Trane XL90 error code table below (or a similar table provided by Trane or the furnace manufacturer) to determine the meaning of the error code:
Error CodeMeaning
1 flashSystem lockout
2 flashesExternal lockout
3 flashesDraft pressure error
4 flashesOpen limit device
5 flashesFlame sensed when no flame should be present
6 flashes115 VAC power reversed polarity or poor grounding
7 flashesGas valve circuit error
8 flashesLow flame sense signal
9 flashesCheck igniter

By interpreting the number of flashes and referring to the error code table, you can identify the specific issue or malfunction indicated by the Trane XL90 furnace.

Please note that the error code table provided above is for illustrative purposes only. Make sure to consult the official documentation or the Trane XL90 furnace manual for the accurate error code meanings specific to your model.

How to Fix Common Trane XL90 Error Codes(General Guidelines)

Fixing common Trane XL90 error codes can often be accomplished with simple steps or troubleshooting techniques. Here are some guidelines for resolving specific error codes:

Error Code 1 – System Lockout: If you encounter error code 1, indicating a system lockout, follow these steps:

  • Turn off the power to the furnace for at least five minutes.
  • Turn the power back on and restart the furnace.
  • If the error persists, check the thermostat settings, the gas supply, and the flame sensor for any issues or malfunctions.

Error Code 4 – Open Limit Device: To address error code 4, which signifies an open limit device, perform the following actions:

  • Inspect the air filter for blockages and clean or replace it as necessary.
  • Check the blower motor and lubricate it according to the manufacturer’s guidelines.
  • Ensure the vent system is free from any obstructions or debris.
  • If the error continues, consider replacing the limit switch after consulting with a qualified HVAC technician.

Error Code 7 – Gas Valve Circuit Error: If you encounter error code 7, indicating a gas valve circuit error, take the following steps:

  • Inspect the wiring connections between the gas valve and the control board.
  • Tighten any loose wires or terminals.
  • If the error persists, consult with a professional to determine whether the gas valve or control board needs replacement.

Please note that the troubleshooting steps provided above are general guidelines. For specific instructions related to your Trane XL90 furnace model and error codes, refer to the official documentation or consult with a qualified HVAC technician. Visual aids such as images or videos can be valuable in understanding the repair process.

How to Prevent Trane XL90 Error Codes

To minimize the occurrence of Trane XL90 error codes and maintain optimal performance of your furnace, follow these preventive measures:

Regular Air Filter Maintenance: Change or clean your air filter every month or as recommended by the manufacturer. This helps maintain proper airflow and prevents debris from affecting the furnace operation.

Professional Furnace Tune-up: Schedule a professional tune-up for your furnace at least once a year before the heating season. A qualified technician can inspect and service the system, ensuring its efficient operation and identifying potential issues.

Thermostat Care: Regularly check your thermostat settings and replace the batteries if needed. Properly functioning thermostats contribute to accurate temperature control and prevent errors.

Clean and Organized Furnace Area: Keep the area surrounding your furnace clean and free of clutter, dust, or flammable materials. This promotes better airflow, reduces the risk of malfunctions, and enhances safety.

Trane Home Diagnostics: Consider opting into Trane Home Diagnostics, a service that allows your dealer to receive real-time information from your system. This enables remote assistance and proactive troubleshooting when necessary.

By following these preventive measures and best practices, you can minimize the occurrence of Trane XL90 error codes and ensure the reliable operation of your furnace.


Q: Why is the light blinking on my Trane XR90?

A: The blinking light on your Trane XR90 furnace indicates an error or issue within the system. Each blink pattern corresponds to a specific error code. By deciphering the number of blinks, you can determine the nature of the problem and take appropriate action to resolve it.

Q: What is error code 90 on Trane thermostat?

A: Error code 90 on a Trane thermostat typically signifies a communication issue between the thermostat and the heating or cooling system. It indicates a disruption in the connection or a malfunction that requires attention. Consult the thermostat manual or contact a qualified HVAC technician for further assistance in troubleshooting and resolving the error.

Q: What is error code 4 on Trane?

A: Error code 4 on a Trane system usually indicates an open limit device. This error suggests that a safety device, such as a limit switch, has detected an abnormal temperature rise within the furnace. To resolve this issue, you should check the air filter, inspect the blower motor, and ensure that the vent system is free from any obstructions or blockages. If the error persists, consider consulting a professional HVAC technician for further evaluation and repair.

Q: What are the codes for a Trane furnace?

A: Trane furnaces utilize error codes to diagnose specific issues within the system. The exact codes can vary depending on the model and version of the furnace. Common error codes for Trane furnaces include system lockout (code 1), external lockout (code 2), draft pressure error (code 3), open limit device (code 4), and more. 

Consult the Trane furnace manual or contact a qualified technician to obtain the accurate list of error codes for your specific Trane furnace model.

Q: What is error code 12 on Trane?

A: Error code 12 on a Trane system typically indicates a communication error or loss of connection between components. It suggests that there might be an issue with the communication wiring, sensors, or control board. To address this error, it is recommended to check the wiring connections and ensure they are properly secured. 

Q: How do I reset my Trane thermostat?

A: To reset your Trane thermostat, you can follow these general steps:

  • Locate the reset button on your thermostat. It is typically found on the front or side of the device.
  • Press and hold the reset button for approximately 5 seconds.
  • Release the button and wait for the thermostat to restart.
  • Once the thermostat has restarted, you can reconfigure the settings according to your preferences.

Please note that the specific reset procedure may vary depending on the model and type of Trane thermostat you have. It is recommended to consult the thermostat manual or contact Trane customer support for the exact steps relevant to your device.

Q: How do I unlock my Trane thermostat code?

To unlock your Trane thermostat code, you can follow these steps:

  • Find the Locked Padlock icon on your thermostat display screen and click on it.
  • The screen will ask you if you want to unlock it. Press OK to proceed.
  • The screen will prompt you to enter the unlock code. This is the same code that you used to lock the thermostat. Use the Up, Down, and Next buttons to insert the code digit by digit and press OK.
  • Your Trane thermostat will now be unlocked and the padlock icon will disappear. You can now change the settings on your thermostat.

If you don’t remember your unlock code, you can try this trick:

  • Locate both the + and buttons on the screen.
  • Then place one of your fingers on the + button and another finger on the button.
  • Press both buttons simultaneously and keep them pressed for about 5 seconds.
  • The thermostat should now be unlocked without a code.

Note that, the specific unlocking procedure may vary depending on the model and type of Trane thermostat you have.  Therefore, we recommend referring to the thermostat manual or contacting Trane customer support for accurate instructions applicable to your particular device.

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