Error Code E42: How to Fix This Honeywell Thermostat Code

A Honeywell smart thermostat is an easy way to better manage how you use your heating and cooling. But like any mechanical system, you may occasionally run into a problem. With the digital display, Honeywell smart thermostats can show an error code that certified technicians will use to get a better sense of what's going on. Here are a few of the most common error codes you may see on your Honeywell smart thermostat.

Honeywell Error Code e42

You can receive this error code if your home’s Wi-Fi internet did not provide an IP address for the thermostat to hook up to. This can occur if the router fails to perform 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 confirming that your router has enabled DHCP. When it does, you might also need to power cycle the router and complete the initial setup process again with the thermostat. Doing so should ensure the DHCP is delivered and connects to the smart thermostat.

Honeywell Thermostat Error e02

Error code e02 appears whenever the password for accessing your home’s Wi-Fi router is not correct. Once this error code appears for 30 seconds, the thermostat’s digital display will automatically progress to the Wi-Fi setup screen so you can try the password again.

How to Fix Honeywell Thermostat Error e02

All you have to do to clear error e02 is verify you’re typing the correct Wi-Fi password when setting up the thermostat.

Error Code 40 for Honeywell Thermostats

Error code 40 can show up when the thermostat is informed that a heat pump or air conditioner’s monitoring system has detected a malfunction. For the most part, this happens if the compressor isn’t turning on despite being instructed to. But this error code can also show up if power is shut off from the outdoor unit for a long period of time. A “High Pressure Fault” error, induced by poor airflow, can display this error code. Finally, you may encounter error code 40 if there’s something wrong 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 ordinary operation. If you reset the thermostat and error code 40 reappears, it's time to contact an experienced technician.

Honeywell Error Code e43

If a Honeywell thermostat displays 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 the 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 recently switched the password or the Wi-Fi’s SSID, which is the name you create for it.

Honeywell Error Code e1

Thermostats utilize sensors to detect the temperature outdoors and indoors. If a sensor malfunctions, you could notice error code e1 show up on your Honeywell smart thermostat.

How to Fix Honeywell Thermostat Error e1

A trained technician can swap out the sensor and restart the thermostat, which should clear error code e1.

Honeywell Thermostat Error 11n

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

How to Fix Honeywell Thermostat Error 11n

A licensed technician can employ a voltmeter to assess if there’s a poor electrical connection. If the wiring on your specific HVAC equipment is bad, the technician can replace it. When the thermostat itself is the source of the error code, it will likely have to be replaced.

Error Code e2 for Honeywell Thermostats

If you see error code e2 appear on your Honeywell smart thermostat, it might mean a few different things. In some cases, one of the sensors that detects the temperature isn’t operating correctly. 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

When the error code is a result of sensor failure, a technician can troubleshoot and replace the damaged sensor. If the problem originates from disconnected power, all you'll need to do is verify the router remains on during the setup process.