IBM Eserver xSeries 360 Type 8686, User Reference Manual

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Chapter 6. Solving Problems
123
Light Path Diagnostics
The Light Path Diagnostics LEDs help you to identify problems with server
components. By following the light path, you can quickly identify and fix the type of
problem that occurred. The light path begins with the LEDs on the operator
information panel (also known as the front LED panel). If the server encounters a
problem, it lights either the Information LED or the Fault LED.
To isolate the source of the trouble, examine the Level 2 Light Path Diagnostics LEDs
through the special cutout on the server top cover (shown at “Level 2 diagnostic panel
LEDs” on page 124). These LEDs can indicate a problem with a single component, or
a problem with one of several similar components. In the latter case, to isolate the
specific failing component, remove the server top cover and look for a lit LED on the
system board or on a component.
For example, if the FAN LED is lit, the specific failing fan is indicated by an LED
viewable with the top cover removed. If the MEM LED is lit, the specific failing DIMM
is indicated by an LED on the memory board.