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

Error Code e42 for Honeywell Thermostats

You might encounter this error code when your home’s Wi-Fi internet did not provide 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 required IP address for your thermostat to link up.

How to Fix Honeywell Thermostat Error e42

You can clear error code e42 by making sure that your router can complete the DHCP. Assuming it does, you might also need to power cycle the router and repeat the initial setup process with your thermostat. This should ensure the DHCP is sent and connects to your smart thermostat.

Error Code e02 for Honeywell Thermostats

Error code e02 occurs whenever the password for communicating with your home’s Wi-Fi router was incorrect. After this error code has appeared for 30 seconds, the thermostat’s digital display should automatically transition to the Wi-Fi setup screen so you can try the password again.

How to Fix Honeywell Thermostat Error e02

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

Honeywell Error Code 40

Error code 40 can appear when the thermostat is notified that a heat pump or air conditioner’s monitoring system has identified a malfunction. For the most part, this happens if the compressor isn’t running despite being directed to. But this error code can also appear if power is shut off from the outdoor unit for an extended period of time. A “High Pressure Fault” error, caused by poor airflow, can render this error code. Finally, you could see 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 check 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.

Honeywell Thermostat Error e43

If a Honeywell thermostat presents error code e43, it can’t communicate with the router, and by extension the Wi-Fi. This might 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 a short period. The thermostat may also be disconnected if you recently changed the password or the Wi-Fi’s SSID, which is the name you provide it.

Honeywell Error Code e1

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

How to Fix Honeywell Thermostat Error e1

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

Honeywell Thermostat Error 11n

Error code 11n can appear if the thermostat is failing to recognize a heating or cooling unit. This might mean that the equipment itself is defective and unable to maintain a connection to 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 find out if there’s a faulty electrical connection. In situations where the wiring on your type of HVAC equipment is bad, the technician can replace it. When the thermostat itself is the source of the error code, it should probably be replaced.

Honeywell Error Code e2

If you’ve noticed error code e2 show up on your Honeywell smart thermostat, it can mean a few different things. In some cases, one of the sensors responsible for detecting the temperature isn’t functioning correctly. In other cases, it means the router was disconnected from power before the thermostat could complete the setup process.

How to Fix Honeywell Thermostat Error e2

In situations where the error code is a result of sensor failure, a technician should troubleshoot and replace the affected sensor. If the problem comes from disconnected power, all you'll need to do is make sure the router remains on over the course of the setup process.