A Honeywell smart thermostat is an easy way to better manage how you use your heating and cooling. But like any utility, you could occasionally experience a problem. With the digital display, Honeywell smart thermostats can display an error code that trained technicians use to figure out what's wrong. Here are several of the most likely error codes you might see on your Honeywell smart thermostat.

Honeywell Thermostat Error e42

You may see this error code when your home’s Wi-Fi internet did not provide an IP address for the thermostat to hook up to. This can occur if your router doesn't perform the Dynamic Host Configuration Protocol, or DHCP. This procedure automatically supplies the needed IP address for your thermostat to link up.

How to Fix Honeywell Thermostat Error e42

You can resolve error code e42 by confirming that your router can complete the DHCP. If it does, you usually also have to power cycle the router and complete the initial setup process again with the thermostat. Completing this task should see to it that the DHCP is transmitted and connects to your smart thermostat.

Honeywell Thermostat Error e02

Error code e02 appears when the password for communicating with your home’s Wi-Fi router is incorrect. Once this error code appears for 30 seconds, the thermostat’s digital display should automatically transition to the Wi-Fi setup screen so you can attempt to enter the password again.

How to Fix Honeywell Thermostat Error e02

All you have to do to resolve error e02 is ensure you’re putting in the correct Wi-Fi password when setting up the thermostat.

Honeywell Thermostat Error 40

Error code 40 can pop up when the thermostat is informed that a heat pump or air conditioner’s monitoring system has detected a malfunction. For the most part, this appears when the compressor isn’t turning on despite being directed to. But this error code can also appear if power is disconnected from the outdoor unit for a long period of time. A “High Pressure Fault” error, induced by poor airflow, can lead to this error code. Lastly, you could encounter error code 40 if there’s something wrong 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 regular operation. If you reset the thermostat and error code 40 reappears, you should try to contact an experienced technician.

Error Code e43 for Honeywell Thermostats

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

How to Fix Honeywell Thermostat Error e43

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

Honeywell Error Code e1

Thermostats utilize sensors to identify the temperature outdoors and indoors. If a sensor fails, you might see error code e1 appear on your Honeywell smart thermostat.

How to Fix Honeywell Thermostat Error e1

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

Error Code 11n for Honeywell Thermostats

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

How to Fix Honeywell Thermostat Error 11n

A qualified technician can use a voltmeter to assess if there’s a faulty electrical connection. If the wiring on your specific HVAC equipment is bad, the technician can replace it. When the thermostat itself is the source of the error code, it will likely have to be replaced.

Honeywell Error Code e2

If you’ve noticed error code e2 appear on your Honeywell smart thermostat, it might mean several different things. Sometimes, one of the sensors used to detect the temperature isn’t functioning correctly. Other times, it means the router was disconnected from power before the thermostat completed the setup process.

How to Fix Honeywell Thermostat Error e2

In situations where the error code is caused by sensor failure, a technician can troubleshoot and replace the impacted sensor. When the problem stems from disconnected power, all you’ll have to do is see to it that the router remains on over the course of the setup process.