Specifications

Power Mac G5 (Late 2005) Troubleshooting — General Information 140
Diagnostic LED Table
LED Description Color When
On
Expected
Condition
LED “On”
Indicates
Things to Check Next Steps
No 1 CPU A Red O CPU A
improperly
installed
Is processor
assembly seated
properly? Check
that mounting
screws are properly
tightened.
Remove processor assembly and
check for damaged pins on processor
connector or logic board connector.
Replace processor, if necessary.
Replace logic board, if necessary.
No 2 Overtemp
LED
Red O CPU has
gone
overtemp
Check that space
is allowed for fans
to ventilate. Verify
fans and sensors
are connected.
Reseat front inlet fan. Run Thermal
Calibration in Apple Service
Diagnostics. Replace processor.
No 3 Power On Red On (with air
deector
open)
Main power
OK and
within
regulation
Check connections
to the power bus
bar.
Check operation of the air deector
sensor. Replace power supply.
No 4 Trickle
Power
Yellow On (with unit
plugged into
AC power and
air deector
open)
AC power
OK
Check for AC
power at the wall
outlet; try another
outlet.
Check operation of the air deector
sensor. Replace power supply.
No 5 Open
Firmware
Good
Green On (with air
deector
open)
CPU arrived
at Open
Firmware
(logic board
is OK)
Reset SMU. Check
for RAM errors.
Check operation of the air deector
sensor. Replace processor. Replace
logic board.
No 6 CPU B Red O CPU B
improperly
installed
(LED 6 only
present on
Quad)
Is processor
assembly seated
properly? Check
that mounting
screws are properly
tightened.
Remove processor assembly and
check for damaged pins on processor
connector or logic board connector.
Replace processor, if necessary.
Replace logic board, if necessary.
No 7 Checkstop Red O
(LED ashes
once at
startup and
then goes o)
CPU hang Check RAM.
Is processor
assembly seated
properly? Check
that mounting
screws are properly
tightened.
Remove processor assembly and
check for damaged pins on processor
connector or logic board connector.
Replace processor, if necessary.
Replace logic board, if necessary.
Notes for LED Table
Power Mac G5 (Late 2005 Dual 2.0/2.3 GHz) logic boards include LEDs 1–5 and LED 7, but not
LED 6. Power Mac G5 (Late 2005 Quad) logic boards include LEDs 1–7.
CPU A is located closest to the PCI Express slots; CPU B is located below CPU A (closer to the
power supply). Make sure CPU screws are tight.
LEDs 3, 4, and 5 operate dierently from the other LEDs. They remain o until you remove
the air deector (clear door inside the side access panel), at which point they should go
on. If LED 3, 4, or 5 is on before you remove the air deector, check the operation of the air
deector sensor. Note that the fans will run at high speed while the air deector is removed.
LED 5 veries that Open Firmware has loaded. To allow time for it to load, be sure to wait at
least one minute from rst power up before you check this LED.
Some logic boards have two additional LEDs: one located near the bottom edge of the logic
board and the other to the right of the top bank of DIMM slots. These LEDs were used only
during manufacturing and should be ignored.
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