Several of the errors that are considered to be critical to the well-being of the Sensor rack continue to display after error status is no longer present. These are referred to informally as "sticky" errors. Sticky errors became a feature of the software in version 3.0 and greater. This is an intentional function of the CEM--it insures that the user acknowledges that a critical error condition was present at some point.
To clear "sticky" errors, hold the [Clear] button down until all error messages are cleared and the second line of the LCD display reads "System OK". This should occur within a couple seconds.
If error messages remain after holding clear for several seconds, you may have an active fault. Call ETC Technical Services for more specific instructions.