5V rails are not working normally when connecting to the I/O board.

Could you give me advice?

My MacBook Air 13 (2015, A1466) has something circuit problem.

The charging lamp is on, when connecting to the power adapter.

But, the computer does not power on and boot.

Then, I am trying to inspect the logic board and fix it.

The situation is below.

PPBUS_GH3 rails: 8.6V

PP3V42_G3H rails: 3.42V

PP5V_S4RS3 rails: 5.1V

PPV5_S0 rails: 5.1V

However, in case LIO Connector "J9500" on the logic board is connecting to the I/O board using I/O board flex cable, 5V rails have a problem.

PPBUS_GH3 rails: 8.6V

PP3V42_G3H rails: 3.42V

PP5V_S4RS3 rails: no 5.1V (The voltage is too low.)

PPV5_S0 rails: no 5.1V ((The voltage is too low.)

Also, the voltage of 1.2V rails and 1V rails are facing with the same situation.

Although I tried to replace both the I/O board and its flex cable with others, the situation does not change.