A Honeywell smart thermostat is an excellent way to better manage how you use your heating and cooling. But like any technology, you could occasionally experience a problem. With the digital display, Honeywell smart thermostats can provide an error code that certified technicians use to get a better sense of what's happening. Here are a few of the most likely error codes you could see on your Honeywell smart thermostat.

Honeywell Thermostat Error e42

You can encounter this error code in the event that your home’s Wi-Fi internet did not provide an IP address for the thermostat to hook up to. This can happen if your router does not perform the Dynamic Host Configuration Protocol, or DHCP. This procedure 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. When it does, you may also have to power cycle the router and repeat the initial setup process with your thermostat. Doing so should ensure the DHCP is sent and connects to the smart thermostat.

Honeywell Thermostat Error e02

Error code e02 appears whenever the password for communicating with your home’s Wi-Fi router is incorrect. 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 to enter the password again.

How to Fix Honeywell Thermostat Error e02

All you'll need to do to clear error e02 is ensure you’re putting in the correct Wi-Fi password when configuring the thermostat.

Honeywell Thermostat Error 40

Error code 40 can show up when the thermostat is alerted 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 directed to. But this error code could also appear if power is shut off from the outdoor unit for an extended period of time. A “High Pressure Fault” error, triggered by obstructed airflow, can display this error code. And finally, you may experience error code 40 if there’s an issue 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 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 displays error code e43, it can’t 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

Restart the router by unplugging it and leaving it that way for about 30 seconds. The thermostat could also be disconnected if you recently switched 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 breaks down, you could notice error code e1 appear 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 clear error code e1.

Honeywell Thermostat Error 11n

Error code 11n can appear when the thermostat can’t recognize a heating or cooling unit. This may mean that the equipment itself is malfunctioning and unable to connect with the thermostat. This sometimes happens when the wiring is bad 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 faulty electrical connection. When the wiring on your type of HVAC equipment is bad, the technician can replace it. When the thermostat itself is the issue, it should probably be replaced.

Honeywell Thermostat Error e2

If you’ve noticed error code e2 pop 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 working like it should. In other instances, it means the router was disconnected from power before the thermostat could complete the setup process.

How to Fix Honeywell Thermostat Error e2

If the error code is caused by sensor failure, a technician should troubleshoot and switch out the impacted sensor. If the problem comes from disconnected power, all you'll need to do is verify the router stays on over the course of the setup process.