Canon imageRUNNERC1022 Service Manual page 200

Chapter 8
Error Codes:
E020 Warning: color displacement/density sensor abnormality
When light could not be received by the light receiver, the machine sets an initial value for the color displacement corrective value, and displays the error
code on the control panel.
Pattern image for color displacement correction
The pattern images are formed on both sides of the ETB certain distance away from the center in the following order.
1) Pattern image for adjustment of LED light intensity
Printed in order of yellow (Y), cyan (C), black (Bk), and magenta (M).
2) Pattern image with slant bars for main-scanning difference measurement
Printed in order of yellow (Y), cyan (C), black (Bk), and magenta (M).
3) Pattern image with horizontal bars for sub-scanning difference measurement
Printed in black (Bk) only on the left side, and in order of yellow (Y), cyan (C), and magenta (M) on the right side.
This is for the comparison of each color registration based on the black position.
8-12
Vertical
synchronous
signal position
Pattern image
for adjustment of LED light intensity
Pattern image with slant bars
for main-scanning difference measurement
Pattern image with horizontal bars
for sub-scanning difference measurement
F-8-17