Why is my Model 231's display saying "Er01" or "ER02"?

The 231MS and 231RS with display options will both display this error if there is a problem within the circuit board or if there is a problem with the display itself. 

ER01 indicates the unit has lost its memory, in a sense. The unit will need to be sent back to the factory to be re-calibrated.

ER02 is also a memory loss error. With the ER02 error, the unit can be re-set by pressing the zero button.

If you need to send the unit back to the factory, a RMA form must be filled out.

Here is the link to the form: https://www.setra.com/support/service