A Honeywell smart thermostat is an excellent way to optimize how you use your home comfort system. But like any utility, you could sometimes experience a problem. With a digital display, Honeywell smart thermostats can display an error code that professional technicians use to figure out what's happening. Here are several of the most known error codes you may see on your Honeywell smart thermostat.

Honeywell Thermostat Error e42

You might see this error code if your home’s Wi-Fi internet did not supply an IP address for the thermostat to hook up to. This can happen if the router fails to execute the Dynamic Host Configuration Protocol, or DHCP. This function automatically supplies the required IP address for your thermostat to connect to the Wi-Fi.

How to Fix Honeywell Thermostat Error e42

You can fix error code e42 by verifying that your router can complete the DHCP. When it does, you may also need to power cycle the router and repeat the initial setup process with the thermostat. Completing this task should ensure the DHCP is transmitted and connects to the smart thermostat.

Honeywell Error Code e02

Error code e02 is displayed when the password for connecting to your home’s Wi-Fi router is incorrect. After this error code appears for 30 seconds, the thermostat’s digital display automatically transitions to the Wi-Fi setup screen so you can try the password again.

How to Fix Honeywell Thermostat Error e02

All you need to do to solve error e02 is verify you’re typing the correct Wi-Fi password when configuring the thermostat.

Error Code 40 for Honeywell Thermostats

Error code 40 can show up when the thermostat is notified that a heat pump or air conditioner’s monitoring system has identified a malfunction. For the most part, this appears if the compressor isn’t turning on despite being directed to. But this error code could also show up if power is disconnected from the outdoor unit for a lengthy period of time. A “High Pressure Fault” error, caused by poor airflow, can lead to this error code. Lastly, you could encounter error code 40 if there’s a problem with the coolant, 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 a Honeywell thermostat presents error code e43, it is failing to communicate with the router, and by extension your Wi-Fi. This could 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

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

Honeywell Error Code e1

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

How to Fix Honeywell Thermostat Error e1

A qualified technician can change out the sensor and reset the thermostat, which should clear error code e1.

Error Code 11n for Honeywell Thermostats

Error code 11n could appear in situations where the thermostat is failing to recognize a heating or cooling unit. This can mean that the equipment itself is malfunctioning and unable to communicate with the thermostat. This sometimes happens 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 existing HVAC equipment is bad, the technician can replace it. In situations where the thermostat itself is the problem, it will likely have to be replaced.

Error Code e2 for Honeywell Thermostats

If you notice error code e2 pop up on your Honeywell smart thermostat, it could mean several different things. In some cases, one of the sensors used to detect the temperature isn’t operating like it should. Other times, it means the router was disconnected from the outlet before the thermostat completed the setup process.

How to Fix Honeywell Thermostat Error e2

When the error code is a result of sensor failure, a technician can troubleshoot and replace the damaged sensor. If the problem stems from disconnected power, all you'll need to do is verify the router stays on over the course of the setup process.