100.01 Services ITU Error, Lexmark C782 - Lexmark C772dn Laser Printer

From the Lemark Service manual

A 100.01 ITU error indicates that the printer did not detect the ITU belt home sensor. Before proceeding with this

service check, make sure that the Second Transfer Roll is correctly installed. After you reinstall the Second

Transfer Roll, check to see if a 100.01 ITU error is still displayed. If a 100.01 ITU error is still being displayed,

continue with this check.

The ITU has an optical sensor that watches for a piece of reflective tape on the inside of the image belt. This

tape is read every revolution of the belt. If a signal is not received from the belt sensor within a certain time

period, the printer posts an error due to the loss of signal. There are several causes for the loss of signal. First,

the belt has tracked too far to the front or rear of the printer. In this case, the belt is still turning, but the reflective

tape is no longer passing within view of the belt sensor. This is considered a belt tracking error and is initially

posted as a 100.02 ITU Error. The other causes of a signal loss could be a belt stall, meaning the belt is not

turning, or a true signal loss, which would be due to a bad sensor, broken cable, loose connection, or bad

system board. These other causes post as a 100.01 ITU Error.

To assist the printer in determining the cause of a signal loss, there is a buffer that records the belt position for

the last 50 revolutions. If the printer loses the belt signal, it refers to the buffer. If the buffer shows significant

mistracking before signal loss, it will post a 100.02 ITU Error. If the buffer shows that the belt has been tracking

in the center before signal loss, it posts a 100.01 ITU Error. Due to memory restrictions, the buffer is not saved

during POR. This means if a printer posts a 100.02 ITU Error, so the belt is tracked off, and the customer or

servicer turns off the printer to clear the error, when the printer starts up, it will still not see the belt signal and will

now post a 100.01 ITU Error because the buffer is empty. When servicing a printer for a 100.01 ITU Error, it is

important to view the error log. See "Display Log" on page 3-29. The error log can only be displayed at this
point. Do not try to print the log. Look for past occurrences of 100.01 ITU Errors preceded by a 100.02 ITU Error.

This applies to the Lexmark C772 and C782 and any model that uses the 40X0343 ITU.
If you get a 100.01 error when installing a new ITU you can probably fix it by adjusting the tracking cam on the ITU. Remove the ITU rotate it so that you are looking at the side that faces the rear of the printer. You will see an adjustment cam and two locking screws. (see photo) Loosen the locking screws 1/4 turn or so. Now adjust the cam. If the belt is tracking too far to the REAR turn the cam COUNTER CLOCKWISE one or two clicks to move it toward the front.
If the belt has been tracking too far forward then turn the cam clockwise.
Tighten the locking screws, reinstall the ITU and run the belt tracking utility. Run the tracking utility twice (it will probably fail the first time because the belt position is changing). If it fails the second time remove the ITU to see if further adjustment is needed. Follow the above steps until the belt tracks properly (i.e. it passes the tracking test).