A Honeywell smart thermostat is an easy way to fine-tune how you use your HVAC system. But like any technology, you might occasionally run across a problem. With its digital display, Honeywell smart thermostats can provide an error code that trained technicians use to get a better sense of what's wrong. Here are several of the most likely error codes you might see on your Honeywell smart thermostat.

Honeywell Error Code e42

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

How to Fix Honeywell Thermostat Error e42

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

Honeywell Thermostat Error e02

Error code e02 appears when the password for communicating with your home’s Wi-Fi router is not correct. Once this error code appears for 30 seconds, the thermostat’s digital display automatically transitions to the Wi-Fi setup screen so you can attempt to enter the password again.

How to Fix Honeywell Thermostat Error e02

All you'll need to do to solve error e02 is verify you’re entering the correct Wi-Fi password when setting up the thermostat.

Honeywell Thermostat Error 40

Error code 40 can appear when the thermostat is alerted that a heat pump or air conditioner’s monitoring system has detected a malfunction. Most commonly, this happens when the compressor isn’t working despite being directed to. But this error code can also show up if power is disconnected from the outdoor unit for a lengthy period of time. A “High Pressure Fault” error, induced by blocked airflow, can render this error code. And finally, you may experience 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 examine the air filter for signs of a clog, as well as the breakers and indoor unit’s blower for ordinary operation. If you reset the thermostat and error code 40 reappears, it’s best to get a hold of an experienced technician.

Honeywell Error Code e43

If a Honeywell thermostat shows error code e43, it is failing to communicate with the router, and by extension your Wi-Fi. This may happen if the router’s ethernet cable isn’t plugged in or it isn’t communicating with the 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 could also be disconnected if you’ve recently updated the password or the Wi-Fi’s SSID, which is the name you give it.

Honeywell Error Code e1

Thermostats employ sensors to determine the temperature outdoors and indoors. If a sensor breaks down, you could see error code e1 appear on your Honeywell smart thermostat.

How to Fix Honeywell Thermostat Error e1

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

Honeywell Error Code 11n

Error code 11n could appear if the thermostat is failing to recognize a heating or cooling unit. This may mean that the equipment itself is faulty and unable to communicate with the thermostat. This can happen when the wiring is defective or even if the thermostat is faulty.

How to Fix Honeywell Thermostat Error 11n

A qualified technician can employ a voltmeter to find out if there’s a bad electrical connection. If the wiring on your specific HVAC system is bad, the technician can replace it. When the thermostat itself is the issue, it should probably be replaced.

Error Code e2 for Honeywell Thermostats

If you see error code e2 show up on your Honeywell smart thermostat, it can mean a couple of different things. For example, one of the sensors that detects the temperature isn’t operating correctly. In other cases, it means the router was disconnected from its power source before the thermostat completed the setup process.

How to Fix Honeywell Thermostat Error e2

When the error code stems from sensor failure, a technician can troubleshoot and swap out the damaged sensor. If the problem comes from disconnected power, all you have to do is make sure the router stays on over the course of the setup process.