IBM NeXtScale nx360 M4 Installation And Service Manual page 38

Any error LED can be lit after ac power has been removed from the system-board
tray so that you can isolate a problem. After ac power has been removed from the
system-board tray, power remains available to these LEDs for up to 90 seconds. To
view the error LEDs, press and hold the light path button on the system board to
light the error LEDs. The error LEDs that were lit while the system-board tray was
running will be lit again while the button is pressed.
The following illustration shows the LEDs and controls on the system board.
DIMM 4-3 error LEDs
DIMM 8-7 error LEDs
RTMM hearbeat LED
Figure 11. LEDs and controls on system board
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IBM NeXtScale nx360 M4 Type 5455: Installation and Service Guide
Microprocessor
HDD 0-3 Error LEDs
Microprocessor 2
error LED
Ethernet card
error LED
mismatch LED
IMM hearbeat LED
Microprocessor 1 error LED
DIMM 2-1 error LEDs
DIMM 6-5 error LEDs
System board
error LED
Lightpath LED
Battery error LED
Slot 1 error LED