Quoting from link to free manual shown:
There are certain conditions that can be interpreted by the circuit board as a failure of the drive motor or motor
position switch. Upon failure detection the control will cease further operation. A telephone hand set symbol will be
shown in the upper left corner of the display and the error code will be shown. Listed below are the different error
1. Motor Always Turning
Error code "E1" occurs when the circuit board detects changes in the motor program switch when the motor is
not supposed to be turning. The phone icon and "E1" will be lit in the display.
2. Motor Never Turns
The Culligan Medallist Series control is equipped to detect no change in the motor position when the motor is
supposed to be turning (motor or piston locked in a frozen position). The AccuSoft circuit board will apply
power to the motor for 20 seconds. If there is no change in the motor homing or position switch, the control will
power down for 1 minute. The circuit board will repeat this procedure two more times in an attempt to remove the
obstruction. If no movement has been detected, the control will permanently power down and a phone icon and
an "E2" will appear in the display.
3. Homing Error
Error code "E3" occurs when the circuit board detects when the control is unexpectedly in the home position.
The phone icon and "E3" will be lit in the display.
Error Display Cancellation
The error code display can be removed by removing the power to the control for 1 minute. After clearing an error
condition, the control will default to the factory settings when power is restored.