Lenovo ThinkCentre M55 Hardware Maintenance Manual - Page 58

3. There are three LEDs to help you determine if the power supply and system board are working correctly. The power button LED is located on the front of the computer and the two diagnostic LEDs are located on the power supply at the rear of the computer. After pressing the power button, observe the LEDs and refer to the following table: Power LED ON OFF Green diagnostic LED ON OFF OFF (after the ON power button has been pressed) ON ON Yellow diagnostic LED OFF OFF OFF Action This is the normal condition of the LEDs when the power is OK. • Make sure the power cord is attached to a working electrical outlet. • Check the power cord for continuity. • If the problem persists, replace the power supply. Replace the system board ON Replace the power supply If the Diagnostic LEDs are in the normal condition and the problem persists, replace the system board and the microprocessor, one at a time, until the computer works correctly. Diagnostic error codes Refer to the following diagnostic error codes when using the diagnostic tests. See "Running tests" on page 43 for the specific type for information about the Diagnostic programs. In the following index, X can represent any number. Diagnostic Error Code 000-000-XXX BIOS Test Passed 000-002-XXX BIOS Timeout 000-024-XXX BIOS Addressing test failure 000-025-XXX BIOS Checksum Value error 000-026-XXX FLASH data error FRU/Action No action 1. Flash the system. See "Flash update procedures" on page 375 2. System board 1. Flash the system. See "Flash update procedures" on page 375 2. System board 1. Flash the system. See "Flash update procedures" on page 375 2. Boot block 3. System board 1. Flash the system. See "Flash update procedures" on page 375 2. Boot block 3. System board 52 Hardware Maintenance Manual