Brother HL-2700CN Service Manual page 263

12 Message "NO TRAY UPP/LOW" is indicated again.
Check Paper Tray PU.
Is Paper Size Sensor Lever damaged ?
Check Paper Size Sensor PU (PSU).
Is PSU properly installed damaged ?
Is connector of Paper Size Sensor disconnected?
Is the connection between Paper Size Sensor
PU and I/O board PU is disconnected?
Replace Paper Size Sensor PU (PSU) .
Is Error Code 12 cleared ?
Replace I/O board PU.
No
Is Error Code 12 cleared ?
Complete
No
No
No
No
No
Yes
VIII-6
Yes
.
Replace the Paper Tray PU.
Yes
.
Replace the Paper Size
Sensor PU.
Yes
.
Connect the connector.
Yes
Yes