A2681 - Repair Assistant / Touch ID sensor

[HeyWatchOutDude]

Hi,

I have a MacBook Air M2 (2022/A2681) here that was missing its Touch ID sensor. I have an OEM Apple replacement, but it isn’t being recognized by the Repair Assistant; it just says 'Touch ID problem'.

Output/Diagnostics:
- Connectivity: Good
- Calibration: Good
- Test Finger: Not Good / Won’t recognize it

Is the only way to 'trigger' the Repair Assistant to order a brand-new Touch ID sensor directly from Apple Self Service?

 

[2informaticos]

Check R2004/5 and their traces.

Did you try another daughter board?
TOUCHID_PWR_EN goes high?

 

[HeyWatchOutDude]

R2004/5 = 20ohms (1.250)
Yes I have tried like 2-3 diffferent boards, I have noticed that PP16V0_TOUCHID_FILT_CONN (0.616) is missing.
TOUCHID_PWR_EN = 1.2V

 

[2informaticos]

Check if LT601 isn't damaged.
Post UT600 voltages; with Touch ID connected.

 

[HeyWatchOutDude]

LT601 is good.

TOUCHID_BOOST_EN (I have checked RT620 and RT0403 all good) = 0V
PP3A8_AON_IPD = 3.8V
PP17V0_LDOIN = 3.4V

 

[2informaticos]

Boost enable comes from Touch ID.
Did you test with known good one?

Just in case, check RT0403.
Also inspect J0401.

 

[HeyWatchOutDude]

Yes, I have used a known good Touch ID.

RT0403 = 0ohms, fine.
J0401 = Also fine.

Is it possible that "TOUCHID_BOOST_EN" only gets enabled when the Touch ID is successfully paired with the Mac?

TOUCHID_INT = 0.306
TOUCHID_PWR_EN = 0.305
SPI_TOUCHID_CLK = 0.585
SPI_TOUCHID_MISO = 0.590
SPI_TOUCHID_MOSI = 0.590

So I guess the (main) logic board can be excluded as "failure point", do you agree?

Everything is present 1.8V LDO, 3.0V LDO except 16.0V LDO and TOUCHID_BOOST_EN.

 

[2informaticos]

I had a problem with missing boost voltage on A2442 machine.
However Tahoe was able to pair it, just not detecting fingerprints.

 

[HeyWatchOutDude]

What else should I try?

 

[2informaticos]

Check diode mode to ground at J0401; compare with good machine.
Also check all the resistors related with SPI_TOUCHID lines; RT0401/3/10-13.