Lenovo IdeaPad U550 - Manual (Page 64)

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Chapter 5. Troubleshooting
The computer enters sleep
mode immediately after
Power-on self-test (POST). • Make sure that:
- The battery is charged.
- The operating temperature is within the acceptable
range. See “Appendix B. Use and care information”
on page 72.
Note: If the battery is charged and the temperature is within range, have the computer
serviced.
The critical low-battery error
message appears, and the
computer immediately turns
off. • The battery power is getting low. Connect the AC
adapter to the computer, or replace the battery with a
fully charged one.
The computer does not
return from sleep mode and
does not work. • If the computer does not return from sleep mode, it
may have entered hibernation mode automatically
because the battery is depleted. Check the power
indicator.
• If your computer is in sleep mode connect the AC
adapter to the computer, then press any key or the
power button.
• If your computer is in hibernation mode or power-off
state. Connect the AC adapter to the computer, then
press the power button to resume operation.
Note: If the system still does not return from sleep mode, your system has stopped
responding, and you cannot turn off the computer, reset the computer. However,
unsaved data may be lost. To reset the computer, press and hold the power
button for 4 seconds or more. If the computer is still not reset, remove the AC
adapter and the battery.