All sharp 1631 and 1642 models have scan unit problem.

Hi,
always "L" code followed by number 1,2,3,4. so if you have L1, L2 or L3 your problem in the optical unit try to remove the copy glass and check the scanner movement by hand. and if the code L4 that mean you have driving machine problem some time this problem cause by toner cartridge so check it .

scan unit can`t move, see the problem

The L1 is indicating a scanner lock.

1. Turn machine off.
2. Make sure the scanner lock is unlocked. This is a clear plastic knob. (it is located on the left hand side of the machine under the document glass in the copy exit area - check your manual for a picture.)
3. Turn machine back on, watch scanner to see if it moves.
4. Try a copy.
5. If you still get an L1 then it might need service because the scanning bar is jammed.

This also is a fix if you are getting blank copies.
Hope that helps...

Background:
The L1 is indicating a scanner lock.

Easy way to fix it:
1. Turn machine off.
2. Turn scan locking switch to unlock. This is a clear plastic knob. (it is located on the left hand side of the machine under the document glass in the copy exit area - check your manual for a picture of it around page 9 or so).
3. Turn machine back on.
4. Try a copy.
5. If you still get an L1 then it might need service because the scanning bar is jammed. They will ask you to try some service codes first to verify that it is indeed jammed. Call 1800 237-4277 for further support.

Followup:
This also is a fix if you are getting blank copies.