A1932 DFU mode error, high fan spin or running but being dead?!?

[dbuergi]

Hi all,

i have a A1932 which entered DFU mode but stopped with an error. For me it looked like a restart but no screen and DFU stopped. I tried a different case with good battery and trackpad but same results.
Sometimes I get a high fan spin with 20v, 2,4a and 12-40w but no screen. The whole board looks clean and I cannot find any corrosion or shorts...
Thermal cam shows CPU at 70-75c so can a defective CPU be the problem or is there anything else I can look for?

[mon2]

Which error?

Remove all power. Meter in resistance mode. Measure the resistance to ground of the VCORE rail.

See attached for DIODE values of assorted power inductors. Red meter probe to ground, yes ground. Black meter probe to point to test. No power during DIODE mode testing.

[dbuergi]

Hello mon2,

i added diode readings to your pic and will test resistance later when i am home again. And i will also add the exact error in DFU. Was something like target device not responding. At this point it also stopped DFU mode.

[dbuergi]

I checked PPVCORE_S0_CPU_PH1 and PH2 both with low resistance at around 12 Ohms.
So no dead CPU right?
Trying DFU again I got the following message:
Unexpected device state 'BootedOS' expected 'DFU' (Probably caused by a transient USB layer issue causing missing or duplicate events) [com.apple.MobileDevice.MobileRestore – 0xFB0 (4016)]

Tried DFU again and it closed without any message and got the closed lock symbol. In this state any action gave me this message with high fan spin.
Can't restore device in this state - please reboot into Recovery or DFU [com.apple.MobileDevice.MobileRestore – 0xFA0 (4000)]

This all happens when battery is disconnected and I use the original power adapter.

Reaching DFU with battery connected I get a blink of a fan spin and the Macbook enters DFU mode.
But it turns out the same way without any fanspin. SSD chips, T2 and CPU are getting hot.


Reaching recovery mode is not possible.

[dbuergi]

One more thing here L7210 and L7230 show constant 0,84v without any drop. As a last effort can reflowing the CPU help? I had other Macbooks where this helped in this case. Or can the fault be somewhere else?
Also i have donor boards with same CPU and SSD but never tried replacing them.