Canon CLC 1120 Service Handbook page 236

CHAPTER 5 SELF DIAGNOSIS
Code
E020
5-8
Cause
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.
The developer has deteriorated.
• The developing cylinder fails to
rotate.
• The developing assembly is not
locked.
• The toner concentration (patch
detection) sensor is faulty.
• The developer inside the
developing assembly is faulty.
• The toner level sensor is faulty.
• The concentration sensor is
subjected to stray light (no cover,
front cover open).
• The photosensitive drum has
deteriorated.
Timing of detection
xx72 During copying sequence, the
level of PT-REF-M/C/Y/K set
initially is '859' or more
because of an error in the
memory backup data.
xx73 During copying sequence, the
level of PT-SIG-M/C/Y set
initially is '749' or more or
that of PT-SIG-K is '371' or
more because of an error in
the memory backup data.
xx74 During copying sequence, the
level of PT-REF-D set
initially is '1000' or more
because of an error in the
memory backup data.
xx75 During copying sequence, the
level of PT-SIG-D set initially
is '1000' or more because of
an error in the memory
backup data.
xx76 During copying sequence, the
level of D-M-TRGT/D-C-
TRGT/D-Y-TRGT (developer
target value) is '930' or more
because of an error in the
memory backup data.
xx80 When samplings are taken
during copying sequence, the
level of WINDOW-M/C/Y/K
(window soiling correction
coefficient) is '130%' or more.
xx81 When samplings are taken
during copying sequence, the
level of WINDOW-M/C/Y/K
(window soiling correction
coefficient) is '70' or less.
xxA0 When samplings are taken
during copying sequence, the
level of SGNL-M/C/Y is '306'
or less.
xxA1 When samplings are taken
during copying sequence, the
level of REF-M/C/Y set
initially decreases (intensity)
by 30% or more.
xxA2 When samplings are taken
during copying sequence, the
level of PT-SIG-K is '51' or
less.