A Honeywell smart thermostat is a great way to better manage how you use your HVAC system. But like any mechanical system, you could sometimes run across a problem. With the digital display, Honeywell smart thermostats can show an error code that trained technicians will use to figure out what's going on. Here are several of the most known error codes you may see on your Honeywell smart thermostat.

Error Code e42 for Honeywell Thermostats

You can encounter this error code when your home’s Wi-Fi internet did not present an IP address for the thermostat to connect to. This can occur if the router does not perform the Dynamic Host Configuration Protocol, or DHCP. This function automatically sends out the necessary IP address for your thermostat to connect to the Wi-Fi.

How to Fix Honeywell Thermostat Error e42

You can resolve error code e42 by making sure that your router has enabled DHCP. When it does, you usually also need to power cycle the router and complete the initial setup process again with your thermostat. Doing so should see to it that the DHCP is transmitted and connects to your smart thermostat.

Honeywell Error Code e02

Error code e02 appears if the password for connecting to your home’s Wi-Fi router is incorrect. Once this error code appears for 30 seconds, the thermostat’s digital display will automatically progress 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 clear error e02 is make sure you’re entering the correct Wi-Fi password when configuring the thermostat.

Honeywell Error Code 40

Error code 40 can pop up when the thermostat is notified that a heat pump or air conditioner’s monitoring system has recognized a malfunction. Most commonly, this occurs once the compressor isn’t working despite being directed to. But this error code may also surface if power is shut off from the outdoor unit for a long period of time. A “High Pressure Fault” error, caused by blocked airflow, can display this error code. And finally, you might see 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 normal operation. If you turn the thermostat off and on again and error code 40 reappears, you should try to get a hold of an experienced technician.

Honeywell Thermostat Error e43

If a Honeywell thermostat displays 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

Reboot 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 Thermostat Error e1

Thermostats employ sensors to identify the temperature outdoors and indoors. If a sensor fails, you could see error code e1 show up on your Honeywell smart thermostat.

How to Fix Honeywell Thermostat Error e1

A skilled technician can swap out the sensor and restart the thermostat, which should resolve error code e1.

Error Code 11n for Honeywell Thermostats

Error code 11n can appear when the thermostat is unable 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 damaged or even if the thermostat has failed.

How to Fix Honeywell Thermostat Error 11n

A qualified technician can utilize a voltmeter to determine if there’s a bad electrical connection. In situations where the wiring on your type of HVAC system is bad, the technician can replace it. In situations where the thermostat itself is the problem, it should probably be replaced.

Error Code e2 for Honeywell Thermostats

If you see error code e2 pop up on your Honeywell smart thermostat, it can mean several different things. Sometimes, one of the sensors used to detect the temperature isn’t functioning properly. In other instances, it means the router was disconnected from power before the thermostat completed the setup process.

How to Fix Honeywell Thermostat Error e2

When the error code is caused by sensor failure, a technician should troubleshoot and swap out the damaged sensor. Any time the problem stems from disconnected power, all you'll need to do is make sure the router stays on throughout the setup process.