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Reflashing the SoC unfortunately did not improve things for this MacBook. I also tried erasing the ROM. No matter which SoC ROM I load, the DFU Restore always ends in the communication error 9.

A2337 820-02016 SoC ROM dump

I just used the U1970 from a working board to make a dump of the ROM. Is there a specific place to deposit this file so others can find it?

Ok. Can you point me to a clean copy of the U1970 SoC ROM file?

This A2337 M1 Air shows no obvious logic board damage but is unresponsive. Without a battery connected, USB-C goes to 20V, then goes blank, then cycles. PPBUS_AON cycles between 12.0 and 12.3V. With a good battery connected, PPBUS_AON is steady at 12.55V. Trackpad clicks intermittently. DFU...

What's your theory of what happened here? How can overcurrent events on PP5V_G3S_DFR_FILT and PP5V_G3S_DFR_FILT cause damage to the Wifi and the USB-C Data chip? Mysterious. I think it's more likely that something else got damaged (CPU? T2?).

Again, no liquid damage on this board. Yes, I get USB power on external devices. USB drives are also recognized when I start up with the option key pressed. Resistors around U3701 look good. Are you suggesting removing the underfilled U3701 and reballing it?

This board came in without liquid damage, but with a missing screen backlight and non-sensitive Touch Bar. I found two burnt & melted inductors (L5100 and L8504) and a burnt via near U8500. Fixing those issues restored the backlight and Touch Bar. But the board is missing Wifi and Bluetooth (no...

I think you're right. I tried running Internet Recovery with Verbose Mode on several times and it always crashes on the CPU test.

I replaced both NAND modules with ones from a donor board, but the exact same symptom persists: spontaneous shutdown during the first 10-20% of the startup progress bar. DFU Restore successful. Apple Diagnostics shows "no issues". Any other ideas?

Yes, the source machine is showing the lightning bolt and the USB logo. The host is set to Show All Devices in Disk Utility. The connection between the two devices is good because I just ran another DFU Restore.

In target disk mode, I get no drive mounted on the host computer. Bad SSD? I have PP2V5_NAND_SSD0 at 2.5V.

Yeah, deep inside the board or the CPU... too bad.

The only other observations are that the original topcase had a malfunctioning Touch Bar (all pixels illuminated simultaneously in one bright bar), the trackpad was not clicking, and the keyboard was non-responsive.

This 2019 Pro behaves in a way I have not seen before. It initially started up to a circle with a line through it. I performed a DFU Restore, which completed successfully (padlock). Now, when I startup using Internet Recovery, the machine gets part way through startup, then the fan blows hard...

EDP_INT_ML_P<1>: 8.1kΩ 0.29 EDP_INT_ML_P<2>: 1.6kΩ 0.28 EDP_INT_ML_P<3>: 1.6kΩ 0.29 EDP_INT_ML_N<1>: 7.8kΩ 0.29 EDP_INT_ML_N<2>: 1.6kΩ 0.28 EDP_INT_ML_N<3>: 1.5kΩ 0.29 EDP_INT_AUX_P: 27.8kΩ 0.28 EDP_INT_AUX_N: OL OL I2C_TCON_SCL: 2.6MΩ 0.49 I2C_TCON_SDA: 2.7MΩ 0.48 I guess there are no shorts...

Just noticed that when the external display is unplugged, I do get steady values on PP5V_S0SW_LCD, EDP_PANEL_PWR_EN, DP_INT_HPD but no display whatsoever.

This A2251 MacBook Pro with mild liquid damage (USB-C area) is working fine on external display but does not recognize the internal LCD. I tried several displays and flex cables, and there is no backlight and no display. The internal does not show up in Settings>Displays, only the camera is...

Never mind. I just found a short in the CPU (DP_INT_AUXCH_C_N). I'm trashing this board.

Correct about my tester screen: it was either the wrong revision or malfunctioning. Connected a known good 2019 display and the keyboard brightness option is back in Settings. However, still no backlight is produced. The output (PPVOUT_S0_KBDBKLT_R) starts at 5.1V, then briefly jumps to 29V...