3. Light path diagnostics panel4. Memory modules5. Microprocessors6. Optical devices (CD or DVD)7. SAS or SATA drivesSee “Running the DSA Preboot diagnostic programs” on page 187 for moreinformation on running the DSA Preboot program on the server.v Troubleshooting by symptomThese tables list problem symptoms and actions to correct the problems. See“Troubleshooting by symptom” on page 190 for more information.Light path diagnosticsThis information describes the light path diagnostics support.Light path diagnostics is a system of LEDs on various external and internalcomponents of the server that leads you to the failed component. When an erroroccurs, LEDs are lit along the path of the front panel, the light path diagnosticspanel, 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 turnedoff, provided that the server is still connected to power and the power supply isoperating correctly.Before you work inside the server to view light path diagnostics LEDs, read thesafety information that begins on page “Safety” on page vii and “Handlingstatic-sensitive devices” on page 37.If an error occurs, view the light path diagnostics LEDs in the following order:1. Look at the operator information panel on the front of the server.v If the check log LED is lit, it indicates that information about an un-isolatedfault condition in the server is available in the IMM event log or in thesystem-event log.v If the system-error LED is lit, it indicates that an error has occurred; go tostep 2.The following illustration shows the operator information panel.ReleasebuttonLight pathdiagnosticLEDsOperator informationpanel2. To view the light path diagnostics panel, press in on the blue release button onthe operator information panel and pull forward on the panel until the hinge of170 System x3750 M4 Types 8722 and 8733: Installation and Service Guide
