User Guide

Mac Pro Troubleshooting — General Information 149
LED 2 CPU B (Lower Processor) Error
LED 3 CPU A (Upper Processor) Error
Normally o. These LEDs come on if an error occurs or if the BootROM is corrupted. They do not
depend on the DIAG_LED button being pressed.
Related symptoms include no video or the computer is hung up. If the BootROM is corrupted,
the optical drive tray should eject, prompting for the insertion of a recovery disc to restore the
BootROM.
Troubleshooting:
With the computer booted, up press the SYS_RST switch. If this clears the CPU Error LED, •
check for incompatible device driver software that may have been installed for added
hardware.
If the Error LED is still on, power down the computer and try pressing the SMC_RST switch. •
Restart the computer.
Reset the power supply by unplugging the AC cord for 10 seconds.•
Unplug AC cord and remove any added DIMMs and PCI Express cards. If this causes the •
LED to go o, repopulate the DIMMs and/or PCI Express cards to nd the combination that
caused the LED to come on. Overheated memory could be a possible cause for this CPU
error LED to come on. Check fan operation.
Unplug the AC cord and remove the battery for 10 seconds. You may need to remove a PCI •
Express card to get to the battery. Reinstall the battery and restart the computer.
Try swapping CPU A and CPU B locations. If the CPU Error LED follows the CPU, replace that •
CPU.
Try replacing the logic board.•
LED 4 CPU B (Lower Processor) Overtemp
LED 5 CPU A (Upper Processor) Overtemp
Normally o. These LEDs come on if an error occurs. They do not depend on the DIAG_LED
button being pressed.
These two LEDs can operate in two dierent modes; they will either ash or stay on. If either
LED is ashing, it may indicate an initial processor over-temperature condition. If either LED is
solidly on, it may indicate a chronic processor over-temperature condition. Initial processor over-
temperature can cause symptoms such as sluggish computer performance. Chronic processor
over-temperature can cause the computer to hang completely. If both LEDs are solidly on at
power up, the power supply cables may be improperly seated.
Troubleshooting:
Verify proper heat sink installation. •
Verify all thermal sensors are properly connected. •
Verify all fans are operating properly, especially the front intake fan.•
Verify power supply cables are properly seated•
If both overtemp LEDs come on immediately when the computer is turned on, a faulty •
power supply could be one cause of this behavior. Replace power supply.