The E1 code indicates lack of communication between the CCC 2 thermostat and the power module boards. The system cannot operate and is about to shut down. Also, it may signal lack of communication between the CCC 2 thermostat and an individual power module board. The code contains the number of zone, which is out of communication, and it will appear on the LED screen. If an additional zone loses contact, it will blink next to the current one.