58 Advanced Troubleshootingw w w . j p . d e l l . c o m | s u p p o r t . j p . d e l l . c o mDiagnostic LightsTo help you troubleshoot a problem, your computer is equipped with fourlights on the back panel labeled "A," "B," "C," and "D" (see page 72). Theselights can be yellow or green. When the computer starts normally, the lightsflash. After the computer starts, the lights remain green. If the computermalfunctions, 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 on page 9.Diagnostic Code Definition Corrective ActionMemory modulesare detected, but amemory failure hasoccurred.• If you have one memory moduleinstalled, reinstall it (see page 82) andrestart the computer.• If you have two or more memorymodules installed, remove the modules,reinstall one module (see page 82), andthen restart the computer. If thecomputer starts normally, reinstall anadditional module. Continue until youhave identified a faulty module orreinstalled all modules without error.• If available, install properly workingmemory of the same type into yourcomputer (see page 87).• If the problem persists, contact Dell(see page 95).Memory modulesare detected, but amemoryconfiguration orcompatibility errorexists.• Ensure that there are no special memorymodule/memory connector placementrequirements (see page 82).• Verify that the memory modules thatyou are installing are compatible withyour computer (see page 87).• If the problem persists, contact Dell(see page 95).Y Y G GA B C DG Y G YA B C D