Diagnostic LEDs

Logic Board Diagnostic LEDs

The Mac Pro (Early 2008) logic board includes a set of LEDs to help service providers troubleshoot the computer. The LEDs are located on the logic board between the two DIMM riser card connectors. LEDs 3, 4, 5, and 6 are normally off and will automatically illuminate if an error occurs. To read LEDs 1, 2, 7, 8, and 9, you must press the DIAG_LED button, which is adjacent to the LEDs. To press the DIAG_LED button, use the nylon probe tool (Apple part number 922-5065).

Powermac Diagnostic LedMac Pro Red Led Logic Board
Use the following table to interpret the LEDs.

Location

Name

Color

Nominal

Press DIAG_ LED button to display

Indicates

Led 1

Sleep

Red

Off; on when computer is in sleep mode

Yes

Sleep mode

Led 2

Standby (Trickle Pwr)

Yellow

On

Yes

Power supply is providing trickle power

Led 3

CPU B Error

Red

Off

No

CPU B halts on an IERR (instruction error)

Led 4

CPU A Error

Red

Off

No

CPU A halts on an IERR (instruction error)

Led 5

CPU B OT

Red

Off

No

CPU B is over temperature

Led 6

CPU A OT

Red

Off

No

CPU A is over temperature

Led 7

GPU Present

Green

On

Yes

EFI has configured the graphics card

Led 8

Power Good

Green

On

Yes

All power rails are functioning

Led 9

EFI Done

Green

On

Yes

EFI is done loading

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