A Power Button Problem; Startup Problems - Lenovo ThinkPad T420 User Manual

2. Swap batteries with another similar model, if available.
If another similar ThinkPad model is available, then verify that the battery pack works in the other
computer and that the battery pack for the other model works in this computer.
3. Verify the battery-status indicator. Refer to "Power-status indicators" on page 12.
The battery-status indicator is normally illuminated whenever the battery is installed and the computer is
on, or the ac power adapter is connected and the battery is charging. This indicator may be blinking or
solid in either orange or green color depending on the status of the battery.

A power button problem

• Problem: The system does not respond, and you cannot turn off the computer.
Solution: Turn off the computer by pressing and holding the power button for 4 seconds or more. If the
system is still not reset, remove the ac power adapter and the battery.

Startup problems

Print these instructions now and keep them with your computer for reference later.
If you receive an error message before the operating system loads, check the following item:
• Follow the appropriate corrective actions for Power-on self-test "error messages." on page 204
If you receive an error message while the operating system is loading the desktop configuration after the
POST is completed, check the following items:
1. Go to the Lenovo Support Web site at: http://www.lenovo.com/support and search for the error
message.
2. Visit the Microsoft Knowledge Base homepage at: http://support.microsoft.com/ and search for the
error message.
Sleep (standby) and hibernation problems
• Problem: The computer enters sleep (standby) mode unexpectedly.
Solution: If the processor overheats, the computer automatically enter sleep (standby) mode to allow
the computer to cool and to protect the processor and other internal components. Check the settings
for sleep (standby) mode, using Power Manager.
• Problem: The computer enters sleep (standby) mode (the sleep/standby indicator turns on) immediately
after Power-on self-test.
Solution: Make sure that:
– The battery is charged.
– The operating temperature is within the acceptable range. Refer to "Features" on page 16,
"Specifications" on page 17, and "Operating environment" on page 18.
If the battery is charged and the temperature is within range, have the computer serviced.
• Problem: The "critical low-battery error" message appears, and the computer immediately turns off.
Solution: The battery power is getting low. Connect the ac power adapter to the computer and plug it
into an electrical outlet, or replace the battery with a charged one.
• Problem: The computer display remains blank after you press Fn to return from sleep (standby) mode.
Solution: Check whether an external monitor was disconnected or turned off while the computer was
in sleep (standby) mode. If you disconnected or turned off the external monitor, connect it or turn it on
before resuming the computer from the sleep (standby) mode. When resuming the computer from the
.
Chapter 10 Troubleshooting computer problems
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