MacBook A2289 820-01987

[mon2]

SMBUS voltages are fine as they are oscillating between 1 and 0s so a typical meter is unable to measure. Will need a logic analyzer to view the I2C traffic commands being sent and received between the devices and the host.

PP1V8_G3S being at 0 volts is of concern. Remove all power. Measure the resistance to ground of PP1V8_G3S.

See attached. U8220 is the loadswitch that enables / disables the PP1V8_G3S power rail.

Carefully, measure the voltage to ground of pin # 2 (P1V8G3S_EN). This is to confirm if the power rail is being enabled or not.

[Zparts01]

I have been so busy I haven't been able to get to it, but thanks mon2 I will check this as soon as I can and write back!

[ugamazing]

Most likely a damaged T2 in this case. You actually can throw any SPI ROM on these to check DFU conflictions. If the original ROM chip was corrupted/damaged, then that leads me even-more to suspect the T2 in this case. I bet the board is cycling during DFU due to T2 losing communications to/with PMU/U7800, or halting due to a damaged internal DFU/restore voltage (which you guys are onto now). The few times I've found one cycling, it was always the T2 at fault. If no liquid were involved, I'd have a bit higher hopes.

[Zparts01]

Thanks ugamazing! I was hoping it was not the T2, but seems that you may be correct. I did try to read the voltage to ground of pin #2 at P1V8G3S_EN and it was cycling from 0.00v - 0.01v and that's it. PP1V8_G3S is reading 0.320 when measuring resistance to ground. Is that the last of the testing I can to verify it's the T2?

[Zparts01]

Power rail is not being enabled or not being enabled mon2. Does this mean T2 is dead?