Canon CLC 1120 Service Handbook page 234

CHAPTER 5 SELF DIAGNOSIS
Code
E020
5-6
Cause
• The toner concentration sensor is faulty.
• The developer inside the developing
assembly is not stirred properly.
• The sensor is subjected to stray light (no
cover, front cover open).
• The photosensitive drum has
deteriorated.
• The window of the toner concentration
sensor is soiled or scratched, or the
protective sheet is soiled.
• The photosensitive drum is soiled (e.g.,
cleaning fault).
The backup data on the CPU PCB is
faulty* or the initial settings have not
been made.
*Be sure to initialize the RAM of the DC-
CPU and enter the values recorded on the
service label.
Timing of detection
xx40 At time of setting initial
data (as during
installation), gain setting
cannot be performed (the
level of SIGG-M/C/Y is
'E0' or more or '20H' or
less).
0441 At time of setting initial
data (as during
installation), gain setting
cannot be performed (the
level of RGAIN-K is 'E0'
or more or '20H' or less).
xx42 At time of setting initial
data (as during
installation, gain setting
cannot be performed (the
level of SIGG-P-M/C/Y/
K is '250' or more or '40'
or less).
xx43 At time of setting initial
data (as during
installation, gain setting
cannot be performed (the
level of RGAN-P-M/C/
Y/K is '250' or more or
'40' or less).
xx50 During copying
sequence, gain setting
cannot be performed
because of an error in the
memory backup data (the
level of SIGG-M/C/Y is
'E0' or more or '20H' or
less).
0451 During copying
sequence, gain setting
cannot be performed
because of an error in the
memory backup data (the
level of RGAIN-K is 'E0'
or more or '20H' or less).
xx52 During copying
sequence, gain setting
cannot be performed
because of an error in the
memory backup data (the
level of SIGG-P-M/C/Y/
K is '250' or more or '40'
or less).