Advanced Troubleshooting 39
Advanced Troubleshooting
Diagnostic Lights
To help you troubleshoot a problem, your computer is equipped with four lights on the back panel 
labeled "A," "B," "C," and "D" (see page 39). These lights can be yellow or green. When the 
computer starts normally, the lights flash. After the computer starts, the lights remain green. If the 
computer malfunctions, the color and sequence of the lights identify the problem.
  CAUTION: Before you begin any of the procedures in this section, follow the safety instructions 
located in the Product Information Guide.
Light Pattern Problem Description Suggested Resolution
The computer is in a normal off 
condition or a possible pre-BIOS 
failure has occurred.
Verify that the computer is plugged 
into a working electrical outlet and 
that you have pressed the power 
button.
A B C D
= yellow
= green
= off