Carrier Performance EDGE Owner's Manual page 53

You get a service reminder message
Service reminder messages - check UV light, check hum pad, check
filter - tell you that it's time to change the UVC lamp in the evaporator
coil box connected to the furnace (when installed), humidifier pad
(when installed), and furnace filter. Make the indicated changes with
the exception of the UV lamp - for important safety reasons, ask your
dealer to replace that.
You get a system error message
Here are the possible system error messages and what they mean:
E1 The system isn't communicating properly. Call your heating and
cooling dealer for service.
-- The temperature sensor isn't working. Call your heating and
cooling dealer for service.
E4 There's an internal memory failure. Call your heating and cooling
dealer for service.
E5 The humidity sensor isn't working. Call your heating and cooling
dealer for service.
II