A Honeywell smart thermostat is an excellent way to better manage how you use your heating and cooling. But like any utility, you might sometimes experience a problem. With its 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 common error codes you could see on your Honeywell smart thermostat.

Honeywell Error Code e42

You can see this error code if your home’s Wi-Fi connection did not present an IP address for the thermostat to hook up to. This can occur if the router fails to complete the Dynamic Host Configuration Protocol, or DHCP. This procedure automatically sends out the required IP address for your thermostat to connect.

How to Fix Honeywell Thermostat Error e42

You can resolve error code e42 by confirming that your router is enabled for DHCP. When it does, you might also have to power cycle the router and perform the setup process again with the thermostat. Doing so should ensure the DHCP is sent and connects to your smart thermostat.

Error Code e02 for Honeywell Thermostats

Error code e02 appears whenever the password for communicating with your home’s Wi-Fi router was incorrect. When this error code has appeared for 30 seconds, the thermostat’s digital display will automatically progress 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 clear error e02 is ensure you’re entering the correct Wi-Fi password when setting up the thermostat.

Error Code 40 for Honeywell Thermostats

Error code 40 can show up when the thermostat is informed that a heat pump or air conditioner’s monitoring system has detected a malfunction. Most commonly, this happens if the compressor isn’t turning on despite being instructed to. But this error code may also show up if power is disconnected from the outdoor unit for a long period of time. A “High Pressure Fault” error, induced by blocked airflow, can display this error code. And finally, you may experience error code 40 if there’s an issue with the coolant, the outdoor unit’s fan motor or the motor’s starting capacitor.

How to Fix Honeywell Thermostat Error 40

You can examine the air filter for signs of a clog, as well as the breakers and indoor unit’s blower for regular operation. If you turn the thermostat off and on again and error code 40 reappears, it's time to get a hold of an experienced technician.

Honeywell Thermostat Error e43

If the Honeywell thermostat displays error code e43, it is unable to communicate with the router, and by extension the 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

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

Honeywell Error Code e1

Thermostats use sensors to determine the temperature outdoors and indoors. If a sensor malfunctions, you might notice error code e1 show up on your Honeywell smart thermostat.

How to Fix Honeywell Thermostat Error e1

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

Error Code 11n for Honeywell Thermostats

Error code 11n can appear if the thermostat is failing to recognize a heating or cooling unit. This can mean that the equipment itself is malfunctioning and unable to maintain a connection to the thermostat. This sometimes happens when the wiring is damaged or even if the thermostat is faulty.

How to Fix Honeywell Thermostat Error 11n

A professional technician can utilize a voltmeter to find out if there’s a bad electrical connection. If the wiring on your existing HVAC equipment is bad, the technician can replace it. If the thermostat itself is the source of the error code, it will likely have to be replaced.

Error Code e2 for Honeywell Thermostats

If you’ve noticed error code e2 pop up on your Honeywell smart thermostat, it could mean a few different things. Sometimes, one of the sensors that detects the temperature isn’t working like it should. In other cases, it means the router was disconnected from power before the thermostat completed the setup process.

How to Fix Honeywell Thermostat Error e2

If the error code stems from sensor failure, a technician will troubleshoot and replace the affected sensor. Any time the problem comes from disconnected power, all you have to do is verify the router remains on during the setup process.