Dell OptiPlex 990 Service Manual page 70

LED
Power Button
Problem Description
Troubleshooting Steps
LED
Power Button
Problem Description
Troubleshooting Steps Re-install all USB devices and check all cable
LED
Power Button
Problem Description No memory modules are detected.
Troubleshooting
Steps
70
• If available, install working memory of the same type
into your computer.
A possible hard drive failure has occurred.
Re-seat all power and data cables.
A possible USB failure has occurred.
connections.
• If two or more memory modules are installed,
remove the modules, then reinstall one module and
restart the computer. If the computer starts
normally, continue to install additional memory
modules (one at a time) until you have identified a
faulty module or reinstalled all modules without
error.