Light path diagnostics

This topic provides an overview of the light path diagnostics LEDs.

Light path diagnostics is a system of LEDs on various external and internal components of the server that leads you to the failed component. When an error occurs, LEDs are lit on the front operator panel on the front of the of the server, then on the failed component. By viewing the LEDs in a particular order, you can often identify the source of the error.

When LEDs are lit to indicate an error, they remain lit when the server is turned off, provided that the server is still connected to power and the power supply is operating correctly.

Before you work inside the server to view light path diagnostics LEDs, read Safety, Installation guidelines, and Handling static-sensitive devices.

If an error occurs, view the light path diagnostics LEDs in the following order:

1. Look at the front operator panel (see Front operator panel) on the front of the server.
   • If the check log LED is lit, it indicates that information about an un-isolated fault condition in the server is available in the IMM event log or in the system-event log.
   • If the system-error LED is lit, it indicates that an error has occurred; go to step 2.
   Note

   Reset button: Press this button on the front operator panel to reset the server and run the power-on self-test (POST). You might have to use a pen or the end of a straightened paper clip to press the button.
2. The modules in the server (on the front and rear) have LEDs that are lit to indicate the location of a problem.

In addition to the light path diagnostic LEDs, the server LCD system information display panel also displays a current list of errors reported by the system and other information. The following is an illustration of the LCD display panel. See the LCD system information display panel for more information about the LCD display panel.

For the location of the LEDs on the modules in the front of the server, see Storage book LEDs, Compute book LEDs, and DIMMs and microprocessor LEDs.

For the location of the LEDs on the modules in the rear of the server, see Half-length I/O book LEDs, Full-length I/O book LEDs, Standard I/O book LEDs, and Power-supply LEDs.

• Storage book LEDs
  Use this information to determine the location of the LEDs on the storage book.
• Compute book LEDs
  Use this information to determine the location of the LEDs on the compute book.
• DIMMs and microprocessor LEDs
  Use this information to determine the location of the DIMMs and microprocessor LEDs.
• Fan LEDs
  This topic provides the location of the fan LEDs.
• Half-length I/O book LEDs
  Use this information to determine the location of the half-length I/O book LEDs.
• Full-length I/O book LEDs
  Use this information to determine the location of the full-length I/O book LEDs.
• Standard I/O book LEDs
  Use this information to determine the location of the LEDs on the standard I/O book.
• Power-supply LEDs
  This topic provides the location of the power supply LEDs.
• Light path diagnostics LEDs description
  This topic provides a description of the light path diagnostics LEDs.