Touch ID not working after Touch IC repair - 6 Plus

[TiptonRepair]

So this is a new one... Got a customer who swears their Touch ID worked before bringing in the device for touch IC repair (Which I have done well over 100 times). After completion, I did my normal checks and noticed Touch ID was not working. I diode mode checked the FPC connector for the home button and everything except for the Pins 1 and 2 were in range. I gently pulled away the silicone from the filter on those 2 connections and low and behold, there were NO filters under the silicone on either side. This was strange to me and I checked 4 other 6+ boards I had and they had filters on them.... So, I put new filters on and check diode mode again and they were all now correct according to ZXW.

I also checked the backplate ribbon to ensure it was good and even tried a new "known good" ribbon just to make sure. Everything checked out. Interestingly enough, the home button does NOT have an Apple logo anywhere on the home button making me believe it was replaced, but the customer swears it has never been touched besides having a few screen replacements on it.

Is there anything else I should look for on their device if they bring it back in? They only gave me about 45 minutes to fix it today and demanded the phone back now... I could barely get all the testing and new filters installed in that time frame, so now I would like to be more prepared for if they come back in.

[Stayboe]

If you go into settings, touch ID & passcode and it is greyed out. I have found It is not getting power from the LDO U2100 or it has an aftermarket home button. I have spent a lot of time on this after getting home buttons mixed up. You can put a genuine home button on even if it doesn't belong to that phone and it will not be greyed out but an aftermarket one will. If it is not greyed out I have had some success by doing an update. If they bring it back in connect it to 3Utools and have a look at the verification report it will soon tell you if the home button has been changed. Hope this helps.

[TiptonRepair]

Thank you for the tip on the 3U verification tools. I went around my shop connecting every phone we have to it and reading it... lol Hopefully she comes back and we can verify everything. If it read a serial number that means the touch ID could work if the serial numbers match, right? If it does not read a serial number, it means the button is not getting power, I assume.

[Stayboe]

These are pics of two phones. One is with an aftermarket home button and the other is with a genuine home button not yet paired to the phone. The aftermarket shows as damaged and the OEM shows as changed.

[TiptonRepair]

So... Customer brought in the device and we have tried 3 home buttons in it. Her original shows no ID, another OEM button from a working phone (screen and all) did not show an ID, and an aftermarket home button... also did not show an ID. I reballed both the home button LDO and the Camera LDO to ensure everything was fully connected. Cameras work correctly. The output of the home button LDO to the FPC connector is 2.9V on boot. All other pins read correctly in Diode mode.

Any other ideas why this thing will not read the Touch ID? Tried a known good ribbon as well. Home button is NOT damaged in any way.

[TiptonRepair]

Just changed the LDO with one from a known good and it now is 1.79V instead of 2.9V making me think the LDO gave up and was outputting full voltage instead of regulating the voltage. Maybe this damaged the Touch ID? Going to find another untouched screen with home button and try that.

[Jessa_the_Professa]

The common fault here is the LDO, but it can be a bitch with the variables when the customer claims fingerprint sensor was working. I would replace the LDO and then look to see if there is any possiblity of OL at any CPU position in the meson heat zone that could affect mesa signaling. If not, refund her and move on---we do an incoming test on fingerprint sensor just to avoid this issue because camera/als/prox/ are all "secondary issue" possibilities after touch ic jobs.

[TiptonRepair]

Yeah, she demanded a new phone...so... yeah. Got to love some customers.

[Jessa_the_Professa]

I hope you told her no way. She came with a phone that had a defect. You don't get "a new phone" because the repair of that defect had an unexplained secondary issue. It is unreasonable to accept the risk of being on the hook for a new phone for every repair. If that is the expectation, then the cost of the repair would go waaaay up.