Dell OptiPlex 360 (Late 2008) - Manual (Page 126)

126 Troubleshooting
Diagnostic Lights
WARNING: Before working inside your computer, read the safety information
that shipped with your computer. For additional safety best practices information,
see the Regulatory Compliance Homepage on www.dell.com at
www.dell.com/regulatory_compliance.
To help troubleshoot a problem, your computer has four lights labeled 1, 2, 3,
and 4 on the front panel.
NOTE: If you are using an ultra small form factor computer, the diagnostic lights
are present on the back panel. See the Setup and Quick Reference Guide that ships
with your computer for more information.
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.
4-3-3 Timer-chip counter 2 failure
4-3-4 Time-of-day clock stopped
4-4-1 Serial or parallel port test failure
4-4-2 Failure to decompress code to shadowed memory
4-4-3 Math-coprocessor test failure
4-4-4 Cache test failure
Code Cause