Lenovo T420i manual Wire Voltage V dc

Wire	Voltage (V dc)
Red	+2.5 to +3.2
Black	Ground

•If the voltage is correct, replace the system board.

•If the voltage is not correct, replace the backup battery.

•If the backup battery discharges quickly after replacement, replace the system board.

36ThinkPad T420 and T420i Hardware Maintenance Manual