A1706 2017 critical update

[iMuhtaseb]

this board suffered from a bad trackpad and bad keyboard after liquid damage; board was turning on no issues..
we've replaced the bad trackpad and bad keyboard no issues whatsoever.. during 2nd final checkup we booted to an external macOS and there started the critical update issue; it boots externally but to the internal SSD it shows critical update; tried Wi-Fi tried Ethernet tried Hotspot same thing..
One weird symptom is it takes too long to power on and show the Apple logo for some reason..

I've taken a look into the MLB and noticed tiny liquid around Q3100.. its the USB-C gate and all ports are OK..
Found liquid on one side of R4201 which is a buck feedback for PMU SoC for Sleep1 SW1.. the resistor itself reads 0 ohms and the side with corrosion is ground and it is also connecting to ground normally..

I have changed the resistor anyway and taken the PMU out and reballed just in case it got liquid under it.. and also because I read on repair wiki that the symptom of critical update AND long post time is most likely liquid under the PMU..

Sadly it did not resolve the issue.. I hate critical update on 2016/2017 models so much..

[mon2]

Check the voltage to ground of the SSD rails.

[iMuhtaseb]

I have taken the measurements with diode mode;
PP1V8_SSD_COLD 0.313
PP1V2_SSD_HOT 0.343
PP1V2_SSD_COLD 0.309
PP1V8_SSD_HOT 0.384
PP0V9_SSD_FIXED 0.307
PP0V9_SSD_REG 0.254

[mon2]

The diode mode readings look ok. Not shorted. Apply power and check the voltage to ground of these SSD rails. This will confirm if the rails are being powered.

[iMuhtaseb]

All are present and stable
PP1V8_SSD_COLD 1.8v
PP1V2_SSD_HOT 1.2v
PP1V2_SSD_COLD 1.2v
PP1V8_SSD_HOT 1.8v
PP0V9_SSD_FIXED 0.9v
PP0V9_SSD_REG 0.9v

[mon2]

Looks good. Apple is anything but logical on their engineering and error messages.

Be sure your internet connection is stable.

Review this thread:

https://forums.developer.apple.com/f...8022#328618022

[piernov]

https://logi.wiki/index.php/Critical...roubleshooting

[iMuhtaseb]

I took measurements from the display and touch connectors for Touch Bar J4402 and J4401 and found on the touch connector J4402 few lines that read high on diode mode and one OL.

DFR_CLKIN_RESET_L was higher that expected
DFR_TOUCH_INT_L also were higher that expected
DFR_TOUCH_CLK_SPI_R was OL

* I compared the numbers from another board and OBD

All returned to the T1 chip.. I've replaced the T1 chip, reformatted the disk and reinstalled latest macOS from the internet to have all the necessary updates bundled with it.. sadly it's still experiencing from the same symptoms.

Unable to install update and long POST times.

[mon2]

Long post time usually means bad bios or speed is throttled due to sensor faults or missing a working sensor.

[iMuhtaseb]

One thing i forgot to mention in my previous post that all lines readings returned to normal as excepted.

i really dont think its a sensor issue since self diagnostic does not show any errors and fan spin on normal speed.

i’ll try getting the bios cleaned up tomorrow.

[iMuhtaseb]

Have not done the bios cleanup cause i found out when i reread the lines again that they were scrambled up again and even worse!
i’ve put another T1 and readings returned to normal.
i put powered the board bare and update is still coming and unable to proceed.. i rechecked the readings they were OK.
i suspect something went wrong with the lines when my colleague replaced the keyboard and its screwing things up.

im not putting the board back to original case and will try to find another top case.

What could ruin the T1 so bad and so direct? I have taken a look at the touch bar cables they were ok.

[iMuhtaseb]

After putting the second T1 chip, I've put the board on a known-good top case and everything went smoothly. 👍

[iMuhtaseb]

One missing feature I found out later was the touch function on the Touch Bar is missing.. display is shown normally, Touch ID is working normally with the paired Touch ID, camera is also working..

I thought the top case is bad but I tried another top case; same symptoms..

I put even a fourth T1 chip and still same issue.. what am I missing here?

Diode mode readings on the touch connector on the board is giving me good numbers as of OBV..

I compared the board around the T1 area for any missing components maybe I have knocked out but no everything is there as it should..

One note that I had two missing (that I fixed from first time) pads under the T1, I also looked for anything missing pads and alright.. missing unconnected pads just that..