ThinkPad T480s, Hardware Maintenance Manual

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2. Turn on the computer. If the computer cannot be turned on, go to “Power system checkout” on page
28, and check the power sources. If an error code is displayed, go to “Symptom-to-FRU index” on
page 35 for error code descriptions and troubleshooting hints.
3. When the Lenovo logo is displayed, repeatedly press and release the F12 key. When the Boot Menu
window opens, release the F12 key.
4. Use the arrow keys to select USB HDD and then press Enter. The diagnostic program will be
launched automatically.
5. Follow the instructions on the screen to use the diagnostic program.
• If you have created the bootable diagnostic medium on a CD, do the following:
1. Turn on the computer. If the computer cannot be turned on, go to “Power system checkout” on page
28, and check the power sources. If an error code is displayed, go to “Symptom-to-FRU index” on
page 35 for error code descriptions and troubleshooting hints.
2. Insert the CD into the optical drive.
3. Restart the computer.
4. When the Lenovo logo is displayed, repeatedly press and release the F12 key. When the Boot Menu
window opens, release the F12 key.
5. Use the arrow keys to select ATAPI CDx (x: 0, 1, ...) and then press Enter. The diagnostic program will
be launched automatically.
6. Follow the instructions on the screen to use the diagnostic program.
Power system checkout
To verify if a battery pack or an ac power adapter is functional, do the following:
1. Turn off the computer.
2. Connect the ac power adapter.
3. Turn on the computer. If the computer can be turned on, it means that either the battery pack or the ac
power adapter is functional.
4. Insert a straightened paper clip into the emergency reset hole to reset the computer. If the computer is
still powered on, it means that the ac power adapter is functional.
5. Turn off the computer.
6. Disconnect the ac power adapter and turn on the computer. If the computer can be turned on, it means
that the battery pack is functional.
If you suspect a power problem, see the appropriate one of the following power supply checkouts:
• “Checking the ac power adapter” on page 28
• “Checking the built-in battery and operational charging” on page 29
• “Checking the coin-cell battery” on page 29
Checking the ac power adapter
You are here because the computer fails only when the ac power adapter is used.
• If the power problem occurs only when the docking station or the port replicator is used, replace the
docking station or the port replicator.
• If the system status indicator does not blink three times when an ac power source is connected, check the
power cord of the ac power adapter for correct continuity and installation.
• If the computer does not charge during operation, go to “Checking the built-in battery and operational
charging” on page 29.
Note: Noise from the ac power adapter does not always indicate a defect.
Checking the USB-C type ac power adapter
To check the USB-C type ac power adapter, do the following:
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T480s Hardware Maintenance Manual