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100 Troubleshooting Tools
– Ensure that the processor power cable is securely connected to the
system board (see "System Board Components" on page 148).
• If the power light is steady amber, a device may be malfunctioning or
incorrectly installed.
– Remove and then reinstall the memory modules (see "Memory" on
page 157).
– Remove and then reinstall any cards (see "Cards" on page 162).
• Eliminate interference. Some possible causes of interference are:
– Power, keyboard, and mouse extension cables
– Too many devices on a power strip
– Multiple power strips connected to the same electrical outlet
Diagnostic Lights
CAUTION: Before you begin any of the procedures in this section, follow the
safety instructions in the Product Information Guide.
To help troubleshoot a problem, your computer has four lights labeled 1, 2, 3,
and 4 on the front panel (see "Front View (Tower Orientation)" on page 21 or
"Front View (Desktop Orientation)" on page 25). When the computer starts
normally, the lights flash, and then turn off. If the computer malfunctions,
use the sequence of the lights to help identify the problem.
NOTE: After the computer completes POST, all four lights turn off before booting to
the operating system.
Diagnostic Light Codes During POST
Light Pattern Problem Description Suggested Resolution
The computer is in a
normal off condition
or a possible pre-BIOS
failure has occurred.
Plug the computer into a working
electrical outlet and press the power
button.