Lenovo E15, FE4A0/FE5A0 NM-C421 REV 1.0 USB C not charge battery  

at the beginning the charging issue should be only the usb C port which is damaged I believe, seems connectivity issue - had good or bad contact when the plug is pressed or bent, till one day totally no power from the usb C.

managed to replace the usb c port. but still no charging. the voltage is always 5V. it seems the power adapter is not communicated properly to lift up the voltage to 20v. connectivity seems all good. tested with a USB c connector tester. connections from all VBUS and CC1, CC2 pins of USB C port to board are all good. CC1/CC2 pins reached U6301 pin 4 and 5.

checked U5901/RTS5455, pin 25 has 5V, pin 26 has 3.3V, pin 10 is 0.16V. voltages of pin 9/CC1 and pin 11 /CC2 are 0.004V and 1.661 V, or vice versa depends on the way that power adapter USB C plug.

please help. thanks.

Does U12502 provide any voltage to ground on pin 4?

U12502 pin 4 has voltage 4.18v to ground.

had some progress. flashed the latest official BIOS, power adapter still remains at 5V, but can charge the battery slowly around 15W when the laptop is on. it shows the battery is charging, the laptop used more power than charging when it's on, so battery level goes down slowly. only when the laptop is off, battery gets charged actually and slowly.

check D12501, reading starts from around 0.9v and stop around1.116v, reverse red and black prob, the reading is around 1.673v. does this mean this diode is bad?

Best would be to remove the diode from the board and measure it outside the circuit.

Vogelek23 napisal/-a:Best would be to remove the diode from the board and measure it outside the circuit.

Yes understand this. Just want to make sure before doing it to avoid making more troubles.

My understanding is at least one reading should be similar to the normal reading around 0.5v, as other diodes around. 2 readings both >1v sounds not right. Am I correct?

This is a 1SS355 diode so its forward voltage drop is actually 1,2V - please check with datasheet. Of course this diode should only show the voltage drop in one direction (red probe to anode, black probe to cathode), that is why I have recommended removing it from the board and measure out of circuit. For the reverse voltage drop in-circuit, something else on the board may obstruct the measurement.

I think I did a bad job when changing the USB-C port, several tiny components are missing from the board - those red circles. and one is misplaced - yellow circle. are they critical for PD?

A= D6311 it was factory not soldered to the board.
B= D6304 it seems also shifted.
C= D6302 - Diode PESD5V0H1BSF
D= D6301 - Diode PESD5V0H1BSF
E= C6310 - Capacitor 100nF/10V, package 0402, ceramic type X7R
F= FL6305 - Common mode filter - it must be aligned to the pads

Diodes B, C, D are an ESD protection diodes and are not critical. The board should work even without these diodes, but I recommend you to solder them for better reliability.
But the missing capacitor "E" and shifted filter "F" are critical and must be soldered / aligned, otherwise the USB Type-C port will not work.