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

Error Code e42 for Honeywell Thermostats

You can see this error code when your home’s Wi-Fi connection did not provide an IP address for the thermostat to connect with. This can occur if a router doesn't perform the Dynamic Host Configuration Protocol, or DHCP. This procedure automatically transmits the necessary IP address for your thermostat to connect.

How to Fix Honeywell Thermostat Error e42

You can clear error code e42 by verifying that your router can complete the DHCP. Assuming it does, you usually also have to power cycle the router and complete the initial setup process again with your thermostat. This should see to it that the DHCP is transmitted and connects to your smart thermostat.

Honeywell Thermostat Error e02

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

How to Fix Honeywell Thermostat Error e02

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

Honeywell Thermostat Error 40

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 occurs when the compressor isn’t working despite being instructed to. But this error code can also surface if power is shut off from the outdoor unit for a lengthy period of time. A “High Pressure Fault” error, triggered by blocked airflow, can render this error code. And finally, you could encounter 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 inspect the air filter for signs of a clog, as well as the breakers and indoor unit’s blower for normal operation. If you restart the thermostat and error code 40 reappears, it’s best to get a hold of an experienced technician.

Honeywell Thermostat Error e43

If your Honeywell thermostat presents error code e43, it is failing to communicate with the router, and by extension the 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

Reboot the router by unplugging it and leaving it that way for about 30 seconds. The thermostat might also be disconnected if you’ve recently switched the password or the Wi-Fi’s SSID, which is the name you create for it.

Honeywell Thermostat Error e1

Thermostats employ sensors to identify the temperature outdoors and indoors. If a sensor fails, you may see error code e1 turn up on your Honeywell smart thermostat.

How to Fix Honeywell Thermostat Error e1

A trained technician can replace the sensor and reboot the thermostat, which should resolve error code e1.

Honeywell Thermostat Error 11n

Error code 11n can appear if the thermostat is unable to detect a heating or cooling unit. This may mean that the equipment itself is malfunctioning and unable to maintain a connection to the thermostat. This sometimes happens when the wiring is defective 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 existing HVAC equipment is bad, the technician can replace it. If the thermostat itself is the problem, it should probably be replaced.

Error Code e2 for Honeywell Thermostats

If you notice error code e2 pop up on your Honeywell smart thermostat, it can mean several different things. Sometimes, one of the sensors used to detect the temperature isn’t working properly. In other instances, 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 is caused by sensor failure, a technician will troubleshoot and swap out the affected sensor. When the problem stems from disconnected power, all you have to do is see to it that the router remains on during the setup process.