A Honeywell smart thermostat is a great way to better manage how you use your home comfort system. But like any utility, you could occasionally experience a problem. With the digital display, Honeywell smart thermostats can display an error code that certified technicians can use to get a better sense of what's wrong. Here are several of the most likely error codes you may see on your Honeywell smart thermostat.

Error Code e42 for Honeywell Thermostats

You may encounter this error code when your home’s Wi-Fi connection did not present an IP address for the thermostat to connect with. This can happen if the router does not perform the Dynamic Host Configuration Protocol, or DHCP. This function automatically supplies the needed IP address for your thermostat to connect.

How to Fix Honeywell Thermostat Error e42

You can fix error code e42 by confirming that your router has enabled DHCP. Assuming it does, you usually also need to power cycle the router and repeat the initial setup process with your thermostat. Completing this task should ensure the DHCP is delivered and connects to your smart thermostat.

Error Code e02 for Honeywell Thermostats

Error code e02 occurs if the password for accessing your home’s Wi-Fi router is incorrect. After this error code appears for 30 seconds, the thermostat’s digital display should automatically transition to the Wi-Fi setup screen so you can try to enter the password again.

How to Fix Honeywell Thermostat Error e02

All you need to do to solve error e02 is make sure you’re putting in the correct Wi-Fi password when configuring the thermostat.

Honeywell Error Code 40

Error code 40 can pop up when the thermostat is alerted that a heat pump or air conditioner’s monitoring system has recognized a malfunction. Most commonly, this appears once the compressor isn’t turning on despite being instructed to. But this error code could also surface if power is shut off from the outdoor unit for a long period of time. A “High Pressure Fault” error, caused by poor airflow, can lead to this error code. Finally, you could see error code 40 if there’s a problem with the refrigerant, the outdoor unit’s fan motor or the motor’s starting capacitor.

How to Fix Honeywell Thermostat Error 40

You can inspect the air filter for signs of a clog, as well as the breakers and indoor unit’s blower for normal operation. If you turn the thermostat off and on again and error code 40 reappears, you should try to get in touch with an experienced technician.

Error Code e43 for Honeywell Thermostats

If the Honeywell thermostat presents error code e43, it is unable to communicate with the router, and by extension the Wi-Fi. This could happen if the router’s ethernet cable isn’t plugged in or it isn’t communicating with the wide area network (WAN).

How to Fix Honeywell Thermostat Error e43

Restart the router by unplugging it and leaving it that way for around 30 seconds. The thermostat might also be disconnected if you’ve recently switched the password or the Wi-Fi’s SSID, which is the name you create for it.

Honeywell Error Code e1

Thermostats utilize sensors to detect the temperature outdoors and indoors. If a sensor malfunctions, you may notice error code e1 turn up on your Honeywell smart thermostat.

How to Fix Honeywell Thermostat Error e1

A trained technician can replace the sensor and reboot the thermostat, which should resolve error code e1.

Honeywell Thermostat Error 11n

Error code 11n may appear if the thermostat is unable to recognize a heating or cooling unit. This might mean that the equipment itself is defective and unable to connect with the thermostat. This can happen when the wiring is damaged or even if the thermostat has failed.

How to Fix Honeywell Thermostat Error 11n

A licensed technician can use a voltmeter to assess if there’s a faulty electrical connection. If the wiring on your specific HVAC system is bad, the technician can replace it. When the thermostat itself is the problem, it should probably be replaced.

Honeywell Thermostat Error e2

If you see error code e2 pop up on your Honeywell smart thermostat, it might mean several different things. Sometimes, one of the sensors responsible for detecting the temperature isn’t working properly. In other cases, it means the router was disconnected from the outlet before the thermostat completed the setup process.

How to Fix Honeywell Thermostat Error e2

In situations where the error code stems from sensor failure, a technician should troubleshoot and switch out the impacted sensor. If the problem originates from disconnected power, all you’ll have to do is verify the router remains on during the setup process.