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

Honeywell Error Code e42

You might encounter this error code when your home’s Wi-Fi connection did not supply an IP address for the thermostat to connect with. This can occur if a router does not complete 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 fix error code e42 by verifying that your router has enabled DHCP. Assuming it does, you usually also have to power cycle the router and repeat the initial setup process with your thermostat. This should see to it that the DHCP is delivered and connects to the smart thermostat.

Error Code e02 for Honeywell Thermostats

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

How to Fix Honeywell Thermostat Error e02

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

Error Code 40 for Honeywell Thermostats

Error code 40 can pop up when the thermostat is informed that a heat pump or air conditioner’s monitoring system has detected a malfunction. Most often, this happens once the compressor isn’t working despite being directed to. But this error code may also appear if power is disconnected from the outdoor unit for an extended period of time. A “High Pressure Fault” error, caused by poor airflow, can lead to this error code. Lastly, you might experience 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 examine the air filter for signs of a clog, as well as the breakers and indoor unit’s blower for regular operation. If you restart the thermostat and error code 40 reappears, you should try to contact an experienced technician.

Honeywell Thermostat Error e43

If your Honeywell thermostat shows error code e43, it can’t 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 around 30 seconds. The thermostat could also be disconnected if you have recently updated the password or the Wi-Fi’s SSID, which is the name you provide it.

Error Code e1 for Honeywell Thermostats

Thermostats employ sensors to identify the temperature outdoors and indoors. If a sensor breaks down, you might notice error code e1 show up on your Honeywell smart thermostat.

How to Fix Honeywell Thermostat Error e1

A skilled technician can replace the sensor and restart the thermostat, which should take care of error code e1.

Honeywell Thermostat Error 11n

Error code 11n can appear when the thermostat can’t detect a heating or cooling unit. This may mean that the equipment itself is faulty 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 use a voltmeter to assess if there’s a bad electrical connection. In situations where the wiring on your specific HVAC system is bad, the technician can replace it. In situations where the thermostat itself is the issue, it will likely have to be replaced.

Error Code e2 for Honeywell Thermostats

If you notice error code e2 appear on your Honeywell smart thermostat, it can mean a couple of different things. In some cases, one of the sensors used to detect the temperature isn’t working like it should. In other instances, it means the router was disconnected from power before the thermostat finished the setup process.

How to Fix Honeywell Thermostat Error e2

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