Lenovo L480 NM-B461: strange power delivery response

[rumpumpel1]

I have a L480 board with a working USB-C port and a non-working docking port that only runs on 5V. I have replaced the TB-Bios but to no avail. Both ports show 0,6V in diode mode. My Kingst Logic Analyzer showed the following strange response.

The charger offers correctly 4 voltages:
0.8781038000,Header,(8589951393),DataObject:4 Source V3 DFP Source_Capabilities
0.8781686000,PayLoad[0],(168923436),V:5V Imax:3A
0.8782978000,PayLoad[1],(1233196),V:9V Imax:3A
0.8784272000,PayLoad[2],(1356076),V:15V Imax:3A
0.8785566000,PayLoad[3],(1458501),V:20V Imax:3.25A

The working USB-C port accepts correctly the last choice:
1.1243578000,PayLoad[0],(1124406597),PD0#4 I:3.25A Imax:3.25A

But the docking port answers with:
1.1165304000,PayLoad[0],(386183168),PD0#1 I:3A Imax:0mA

How should I proceed?

[rumpumpel1]

schematics can be found here: https://www.badcaps.net/forum/troubl...l580-el480-tvw

[mon2]

You are defaulting to the 5V power on default power delivery contract. The same that you would have if the power delivery controller is not present or defective on the host logic board. The PD communication is over the CCx lines (single wire biphase communication).

Remove all power. Meter in DIODE mode. Red meter probe to ground, yes red.

Black meter probe to the CC1 pin. What is the diode mode measurement?

Repeat with the CC2 pin. Repeat with the working & non-working ports. We are checking if the the TVS ESD diode(s) are defective that may be impacting the communication of the PD contracts.

Post each measurement.

[rumpumpel1]

sorry for my bad description, but the diode measurement gave 0,6V for all 4 possibilities.