IBM X21, X23, X24, X22, X20 manual Following table shows the test for each FRU

Standby status	Green:The computer is in standby mode.
	Blinking green: The computer is entering
	standby mode or hibernation mode, or is
	resuming normal operation.
Bluetooth(X23,	Green:The Integrated Bluetooth features are
X24 Bluetooth	on.
Model Only)
	Blinking green:The Integrated Bluetooth
	features are functioning.
Bluetooth	Press this button to turn the IBM Integrated
power button(X23,	Bluetooth on and off.
X24 Bluetooth
Model Only)
Drive in use	Green:Data is read from or written to the
	hard disk drive, diskette drive, or drive in the
	Ultrabay 2000.
Num lock	Green:The numeric keypad on the keyboard
	is enabled.
Caps lock	Green:Caps Lock mode is enabled.
Scroll lock	Green:Arrow keys can be used as
	screen-scroll function keys.
Power on	Green:The power is on.

The following table shows the test for each FRU.

FRU	Applicable test
System board	1.	Diagnostics -->CPU/Coprocessor
	2.	Diagnostics -->Systemboard
Power	Diagnostics --> Other Devices --> IBM AC
	Adapter, IBM Battery
LCD unit	1.	Diagnostics -->Video Adapter
	2.	Interactive Tests -->Video

Chapter 3. ThinkPad X20, X21, X22, X23, X24 45