HP 2000CP 2500CP - Manual (Page 101)

Service Tests 4-15 HP DesignJet CP Series Printers
In this case, try one of the following:
1 Clean the Mark Encoder if necessary.
2 Make sure the Line Sensor is installed correctly.
3 Perform the Service Accuracy Calibration
' Page 5-17.
4 Replace the lens cover which is installed on the line sensor.
5 Replace the Trailing Cable
' Page 8-36.
6 Replace the Carriage Assembly
' Page 8-42.
7 Replace the Electronics Module ' page 8-6.
Only replace one component at a time and check if the error has
gone before replacing another component. Using this procedure
you will be able to determine exactly which component failed.