Solving Problems 195
Diagnostic Lights
When you turn on your computer, it performs a series of self-diagnostic
checks. A successful POST ends with a single beep that si gnifies the start of
normal operation. If the computer fails to complete the POST, a series of
lights located on the computer can help you understand which test failed or
why the computer stopped responding. These lights communicate problems
encountered before and during POST only, not during normal operation. To
locate the diagnostic lights, see "Front View of the Computer (Doors
Open)."
The following tables lists the codes for the diagnostic lights, gives probable
causes, and suggests corrective actions. The lights are labeled to help you
match the pattern on your computer with one shown in the tables:
• Diagnostic Light Codes Before POST
• Diagnostic Light Codes During POST
Preboot Diagnostic Codes
The following table lists the codes for the diagnostic lights that occur before
the computer begins the POST.
Diagnostic Light Codes Before POST
Light Pattern Cause Action
No electrical power is supplied to the
computer. Connect the computer to its electrical outlet. Ensure that
the front-panel power light is on. If the power light is off,
ensure that the computer is connected to a working
electrical outlet and then press the power button.
If the problem is still not resolved, contact Dell for
technical assistance.
A B C D
= yellow
= green
= off