I had the same problem and want to complete this thread
PM_PWRBTN_L 3.41V and drops to about 0V by pressing power button
PM_SLP_S4 is directly after plug in the power cord 3.41V
PM_SLP_S3 is directly after plug in the power cord 3.41V as well
all S3 voltages listed in the schematics are present
PP12V_S0 was only 2,17V
U8450 Pin 2 PM_EN_FET_P12V_S0 was only 2.17V and in diode mode short to ground
after replacing U8450 I got on Pin 2 PM_EN_FET_P12V_S0 3.3V but still no progress
So I still replaced Q8450
and all problems are gone
System is working properly now.
PM_PWRBTN_L 3.41V and drops to about 0V by pressing power button
PM_SLP_S4 is directly after plug in the power cord 3.41V
PM_SLP_S3 is directly after plug in the power cord 3.41V as well
all S3 voltages listed in the schematics are present
PP12V_S0 was only 2,17V
U8450 Pin 2 PM_EN_FET_P12V_S0 was only 2.17V and in diode mode short to ground
after replacing U8450 I got on Pin 2 PM_EN_FET_P12V_S0 3.3V but still no progress
So I still replaced Q8450
and all problems are gone
System is working properly now.