For $29/mo, we provide access to advanced level technicians who will answer your questions on any Macbook board related matter to the best of their knowledge promptly & walk you through how to solve your problem so you can deliver a working board to your customer.
PCH requires some basic signals and voltages, in order to start power on sequence.
In fact, it doesn't reply to power button at all.
All previous checks assured that PCH receives all these.