IBM eserver xSeries 350 User Reference Manual page 21

LED panel for more detailed information (see "System board LED locations and
diagnostic LED panel" on page 36).
System error: This amber light is on when a system error occurs. A light on the
diagnostic LED panel will also be on to further isolate the error. (For more
information, see "Chapter 6. Solving problems," on page 79.)
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Chapter 1. Introducing the xSeries 350 server