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.
Then the problem is PCH related.
Check its basic signals; PM_BATLOW_L, PM_DSW_PWRGD, PCH_DSWVRMEN, SMC_ADAPTER_EN, PM_RSMRST_L and the 4 DC RTC signals.
Are you really sure no pulse at PM_SLP_S4_L, nor PM_SLP_S3_L?
In such case, PCH internal failure.
You can try to heat it (adding quality flux) and pray...