ASUS X555LD Rev:2.0
Customer brought me this laptop and said its automatically turned off within few seconds after start it.
When I switched on, it starts with fan spinning speed increase and decrease few times (5 or 6 times) and stayed at full speed for around 30-60 seconds and turned off automatically.

The steps I have followed,
Replaced a fan (nothing changed)
Replaced U5003 - TEMP. SENSOR NCT7717U - (nothing changed)
Replaced Q2804 - Signal to IO - (nothing changed)
Replaced IT8585E/FX and flash EC (nothing changed)
Removed Q3201 (PLT_RST#, EC_RST#) (nothing changed)
Flashed U2803 SPI BIOS (nothing changed)

The only thing I have noticed is SECFB charge pump voltage is varied little.
When the fan spinning is changing is becomes 13.4v to 12.3v and when the fan is at maximum speed it stayed 13v constantly.

This +12VS delivers the data from CPU thermal sensor and I suspec due to this voltage change it doesn't communicate properly.

Please suggest me next step. Thanks

Please tell me the voltage of PU8100 (3.3/5v) pin 13?