A Honeywell smart thermostat is an excellent way to better manage how you use your heating and cooling. But like any utility, you might occasionally experience a problem. With a digital display, Honeywell smart thermostats can provide an error code that trained 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 Thermostat Error e42

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 take place if a router doesn't execute the Dynamic Host Configuration Protocol, or DHCP. This function automatically transmits the needed 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 making sure that your router is enabled for DHCP. If it does, you may also have 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 your smart thermostat.

Honeywell Thermostat Error e02

Error code e02 appears if the password for accessing your home’s Wi-Fi router is not correct. When this error code has appeared for 30 seconds, the thermostat’s digital display automatically transitions 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 ensure you’re putting in the correct Wi-Fi password when setting up the thermostat.

Honeywell Thermostat Error 40

Error code 40 can show up when the thermostat is notified that a heat pump or air conditioner’s monitoring system has detected a malfunction. Most commonly, this happens once the compressor isn’t running despite being instructed to. But this error code can also surface if power is shut off from the outdoor unit for a long period of time. A “High Pressure Fault” error, induced by blocked airflow, can lead to this error code. Lastly, you might encounter error code 40 if there’s a problem with the refrigerant, 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 normal operation. If you reset the thermostat and error code 40 reappears, you should try to get a hold of an experienced technician.

Honeywell Thermostat Error e43

If a Honeywell thermostat shows error code e43, it can’t 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

Restart 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 give it.

Honeywell Thermostat Error e1

Thermostats use sensors to detect the temperature outdoors and indoors. If a sensor malfunctions, you may see 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 reset the thermostat, which should resolve error code e1.

Honeywell Thermostat Error 11n

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

How to Fix Honeywell Thermostat Error 11n

A professional technician can employ a voltmeter to assess 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. In situations where the thermostat itself is the issue, it will likely have to be replaced.

Honeywell Thermostat Error e2

If you see error code e2 appear on your Honeywell smart thermostat, it could mean several different things. Sometimes, one of the sensors that detects the temperature isn’t operating properly. Other times, it means the router was disconnected from the outlet before the thermostat completed the setup process.

How to Fix Honeywell Thermostat Error e2

In situations where the error code stems from sensor failure, a technician will troubleshoot and replace the impacted sensor. When the problem stems from disconnected power, all you'll need to do is make sure the router remains on during the setup process.