Lexmark 4090-001 - Manual (Page 27)

Diagnostic Aids 3-2
4090-001
Encoder Sensor Test
This test disables the printer motors to allow you to manually move
the carrier to verify the encoder is working correctly.
To run the test:
1. Turn the printer off and place a two pin jumper on connector J6
as shown below. (Pins 1 & 2)
2. Press and hold the Paper Feed button while turning the
printer on, to start the test. Release the button when the printer
completes POST. Turn power off or unplug the printer to stop
the test.
The power light flashes as the carrier is moved. The busy light
remains on for right to left, and blinks for left to right movement. With
no carrier movement, the busy light indicates the direction of the last
move. If the test fails, power off the printer and remove the carrier
assembly without unplugging the printhead cable.
Power on the printer and check for +5 V dc at pins 1, 2 and 3 of the
encoder card connector.
1. If voltage is not present, check the printhead cable for opens to
the encoder card. If the printhead cable is good, replace the
system board.
2. If voltage is present, check the sensor on the encoder card by
monitoring pin 3 of the encoder card connector as you pass a
piece of paper through the sensor. The voltage should go from
+5 V dc to 0 V dc. Turn the power off and back on to make this
check again. If the voltage at pin 3 does not change, replace the
encoder card. If the symptom remains, replace the printhead
cable.