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32 Quick Reference Guide
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Diagnostic Lights
CAUTION: Before you begin any of the procedures in this section, follow the safety instructions in the
Product Information Guide.
To help you troubleshoot a problem, your computer has four lights labeled "1," "2," "3," and "4"
on the front or back panel. The lights can be "off" or green. When the computer starts normally,
the patterns or codes on the lights change as the boot process completes. When the computer
starts normally, the patterns or codes on the lights change as the boot process completes. If the
POST portion of system boot completes successfully, all four lights display solid green for a short
time, and then turn off. If the computer malfunctions during the POST process, the pattern
displayed on the LEDs may help identify where in the process the computer halted. If the
computer malfunctions after a successful POST, the diagnostic lights do not indicate the cause
of the problem.
NOTE: The orientation of the diagnostic lights may vary depending on the system type. The diagnostic
lights can appear either vertical or horizontal.
Light Pattern Problem Description Suggested Resolution
The computer is in a normal "off"
condition, or a possible pre-BIOS failure
has occurred.
The diagnostic lights are not lit after the
computer successfully boots to the
operating system.
Plug the computer into a working
electrical outlet and press the power
button.
A possible BIOS failure has occurred; the
computer is in the recovery mode.
Run the BIOS Recovery utility, wait for
recovery completion, and then restart the
computer.
A possible processor failure has occurred. Reinstall the processor and restart the
computer.
For information on reinstalling
the processor, see your online
User’s Guide
.