32 IBM Desktop System HMMIndex of Symptoms, Messages, ErrorCodes, or BeepsHow to Use Error Messages: Use the messages,error codes, and beeps combinations that occur todiagnose failures. If more than one failure occurs,begin the diagnosis from the first failure thatappeared. The cause of the first failure can result infalse messages, error codes, or beeps. If you did notreceive any messages, error codes, or beeps, see ifthe symptom is listed in “Table 2-3 Error SymptomsList” on page 38.CAUTION: When you have deemed it necessary toreplace a FRU, and have done so, you mustrun a total system check to ensure that noother activity has been affected by the change.This system check can be done through thediagnostics program (Select Diagnostics, thenselect and execute All Tests from PC-Doctor).POST: Some diagnostic aids are resident in themachine, such as the Power-On Self Test (POST).The machine performs the POST each time it ispowered on. Use this information throughout thediagnostic procedures. The POST is a series ofsystem checks and initializations that verify thecorrect operation of the base system.After a successful POST, the system attempts to loadthe operating system. The system can be customizedfor different startup (boot) methods by the BIOSConfiguration/Setup Utility. See “BIOS Configuration/Setup Utility” on page 12.The system's default startup sequence automaticallylooks for the operating system files in the hard disk ifthese files are not found in the diskette.WARNING: Remember that POST does not test allareas, but only those that allow the system tooperate well enough to run the diagnosticsprogram.Table 2-1 lists BIOS error codes, messages, and theirpossible causes. Table 2-2 lists BIOS beeps and theirpossible causes. Table 2-3 lists error symptoms andtheir possible causes. The most likely cause is listedfirst. Make sure you complete all items in the cause or
