Lenovo ThinkPad T490s Hardware Maintenance Manual page 36

• 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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T490s and X390 Hardware Maintenance Manual
Wire Voltage (V dc)
Red +2.5 to +3.2
Black Ground