Quick Reference Guide 37Error MessagesNOTE: If the message is not listed, see the documentation for either the operating system or the programthat was running when the message appeared.If an error occurs during start-up, a message may be displayed on the monitor identifying theproblem. See "Error Messages" in the User’s Guide for suggestions on resolving any problems.Diagnostic LightsCAUTION: Before you begin any of the procedures in this section, follow the safety instructions in theProduct Information Guide.To help you troubleshoot a problem, your computer has four lights labeled "1," "2," "3," and "4" onthe front. The lights can be off or green. When the computer starts normally, the lights flash. Afterthe computer starts, all four lights display solid green briefly and then turn off to indicate normaloperation. If the computer malfunctions, the pattern of the lights identify the problem.3-4-2 Screen retrace failure3-4-3 Search for video ROM failure4-2-1 No timer tick4-2-2 Shutdown failure4-2-3 Gate A20 failure4-2-4 Unexpected interrupt in protected mode4-3-1 Memory failure above address 0FFFFh4-3-3 Timer-chip counter 2 failure4-3-4 Time-of-day clock stopped4-4-1 Serial or parallel port test failure4-4-2 Failure to decompress code to shadowed memory4-4-3 Math-coprocessor test failure4-4-4 Cache test failureLight Pattern Problem Description Suggested ResolutionThe computer is in a normal offcondition or a possible pre-BIOS failurehas occurred.NOTE: The diagnostic lights turn off aftera short time if the computer is in a normaloperating condition after POST.Plug the computer into a workingelectrical outlet and press the powerbutton.Code Cause
