Samsung MultiXpress M537x series Service Manual page 304

4. Troubleshooting
► Error Code
S3–3121
► Error message
Scanner locked or another problem occurred.
► Symptom
Scanner module does not move.
► Troubleshooting method
1) Open the DSDF unit.
2) Check if the scan locking switch is in lock status. Release it. Close the DSDF unit.
3) Remove the rear cover. Check if the connector on the main board is connected correctly.
4) Remove the scan glass.
5) Check if the home position sensor cable is connected correctly.
6) If the problem persists, replace the main board.
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