Damaged insulation of the wire unit of the temperature sensor (reference 1 & 3 image) which measures the temperature of the water cooling block of the light pipe entrance. When disconnecting the wire unit (reference 1 image) of the temperature sensor from the Signal Backplane the error code is changed to “light pipe - temperature sensor open”.

1. Repair the insulation of the wire unit using shrink sleeve.

2. If not repairable, replace the whole wire unit and temperature sensor.

Defect temperature sensor (reference 3 image) on the water cooling block of the light pipe entrance. When disconnecting the wire unit (reference 1 image) of the temperature sensor from the Formatting Interface Board the error code is changed to “light pipe - temperature sensor open”.

Replace the temperature sensor.

Malfunction Fan Control board.

Replace the Fan Control board. See "Replacement of a Card Cage board".