User Guide

Mac Pro Troubleshooting — General Information 14 8
Use the following table to interpret the LEDs.
Location Name Color Nominal Press DIAG_
LED button
to display
Indicates
Led 1 Trickle Pwr Yellow On Yes Power supply
is providing
trickle power
Led 2 CPU B Error Red O No CPU B halts
on an IERR
(instruction
error)
Led 3 CPU A Error Red O No CPU A halts
on an IERR
(instruction
error)
Led 4 CPU B OT Red O No CPU B is over
temperature
Led 5 CPU A OT Red O No CPU A is over
temperature
Led 6 GPU Present Green On Yes EFI has
congured
the graphics
card
Led 7 Power On Green On Yes All power
rails are
functioning
Led 8 EFI Done Green On Yes EFI is done
loading
Note: There is a position on the logic board next to LED 1 for a SLEEP LED that does not have
any LED installed. This is normal; the LED was used only in development. To determine if a Mac
Pro computer is in sleep mode, watch the power LED on the front of the computer. It will slowly
change brightness levels if the computer is sleeping.
LED 1 Trickle Power
Normally on when DIAG_LED button is pressed.
If LED 1 is not on, the symptom would be that the computer won’t power on.
Troubleshooting:
Check AC cord is connected to a working AC wall outlet. •
Reseat AC Plug.•
Check connections of power supply cables to the logic board. •
Check power supply cable connections at power supply. •
Replace power supply.•