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.
This 2015 Air board generates all power rails, Vcore, ALL_SYS_PWRGD, and PM_SLP_S4_L. Fan spins but does not POST, chime, or start up. The only abnormal signals I noticed are SMC_PROCHOT = 3.4 and CPU_PROCHOT_L = 0. Any ideas?
Check all SPI Bus Series Termination resistors and their traces.
Inspect board for corrosion.
Check it outside of shell, only charger and USB device for test.
Do not connect LIO flex, nor SSD and airport card.