Lenovo ThinkPad X1 Carbon Gen 10 Hardware Maintenance Manual page 34

• If the voltage is correct, replace the system board.
• If the voltage is not correct, replace the coin-cell battery.
• If the coin-cell battery discharges quickly after replacement, replace the system board.
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XXX Hardware Maintenance Manual
Wire Voltage (V dc)
Red +2.5 to +3.2
Black Ground