Rain Bird ISM Instruction Manual page 41

SYMPTOM
LCD display shows
"Err" for a few seconds
and then shows the
station operating for a
few seconds.
ISM Installation, Programming & Operation Guide
POSSIBLE CAUSE
17. Same as Cause #16.
CORRECTION
start relay can also produce a momentary overload
that may be detected by the controller.
Locate and repair the cause of the short circuit. Press
enter with dial in SYSTEM ON position when "Err" is
displayed.
See correction for Cause #16.
Page 41