Canon CLC 1120 Service Handbook page 232

CHAPTER 5 SELF DIAGNOSIS
Code
E020
5-4
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.
Timing of detection
xx13 At time of setting initial data
(as during installation), the
variation of REF-M/C/Y
levels for ten concentration
data samplings is '70' or more.
xx16 At time of setting initial data
(as during installation), the
variation of PT-SIG-M/C/Y
levels for 16 concentration
data samplings is '102' or
more.
xx17 At time of setting initial data
(as during installation), the
variation of PT-REF-M/C/Y
levels for 16 concentration
data samplings is '70' or more.
xx20 At time of setting initial data
(as during installation), the
result of averaging samplings
of SGNL-M/C/Y levels is
'777' or less.
xx21 At time of setting initial data
(as during installation), the
result of averaging samplings
of REF-M/C/Y levels is '200'
or less.
xx23 At time of setting initial data
(as during installation), the
result of averaging samplings
of PT-REF-M/C/Y levels is
'777' or less.