iPhone 13 screen replacement disables Face ID in iOS15. Why does this happen?

iPhone 13 screen replacement disables Face ID in iOS15. Why does this happen?

It has been confirmed Apple have made a u-turn on their technology which links the iPhone 13 screen to Face ID. When the iPhone 13 was originally released, replacing the screen from another iPhone 13 (pro models included) would cause Face ID to be disabled, but why?

This is because the microchip which controls the iPhone 13 screen is not only communicating with the iPhone itself but also with the iPhone’s Facial recognition (Face ID). Removing the screen breaks this chain of communication. iOS15 then disables Face ID because of the communication break. Is this a new software bug? Or an insight of what’s to come?

To understand this technology further we have to go back to how Apple used to control their screens and how this technology has advanced over the years. From our research the iPhone communicates with the screen through a microchip embedded on the screen. 

This screen microchip is an integrated circuit (an assembly of electronic components fabricated into a single unit) responsible for translating your analogue touch (your finger pressing on your screen creating an analogue signal) to a digital signal (for your iPhone to understand as your iPhone is a mini computer and doesn’t understand analogue signals). 

From the inception of the iPhone the integrated circuit (or circuits for the plus size iPhone 6) were always placed on the logic board of the iPhone (the logic board is the iPhone’s brain). In the iPhone 6s Apple moved this ADC (analogue to digital converter) Ic (integrated circuit) to the screen. From then the screen would communicate directly to the iPhone’s central processing unit (the iPhone’s CPU is something we’ll discuss in the future). 

The iPhone X was Apple’s first OLED screen on an iPhone and with it came an advancement in Apple’s screen integrated circuit. We found that not only did the circuit act as an ADC, converting your touch signal but now also was responsible for activating the colour saturation for True Tone. This feature was previously serialised into the ambient light sensor on the iPhone 8. But with the iPhone X the central processing unit communicated directly with the screen ic to confirm activation of True Tone.

This was tested and confirmed by replacing an original iPhone X screen with another iPhone X screen. The replacement screen then lost it’s True Tone feature. Apple achieved this True Tone activation through the use of an EEPROM (an Electronically Erasable Programmable Read Only Memory chip). They built it into the screen’s microchip (technically it’s burned into the circuit, but that’s a discussion for another day, I’ll try to keep this as non-technical as possible). 

The iPhone’s CPU (central processing unit) would read a code within the EEPROM to activate True Tone. If you turned on an iPhone X with a replacement screen, even an original, it was unable to read the correct code (a serial number) and therefore unable to activate True Tone. 

To further understand how complex these microchips can get, think of the integrated circuit as a multi-story building. The more complex the circuit, the more floors the building has. We said earlier we’d discuss Apple’s central processing unit in another blog in the future. Just to put this into perspective, Apple’s new silicon CPU’s are like skyscrapers of circuitry. Back to the screen’s IC & True Tone. 

As the type of memory chip used to store this True Tone data in the iPhone X was readable, erasable & programmable, the Chinese quickly found a way of copying this data. Originally this data could only be copied from one original screen to another, but over the years we have seen this code have the ability to be transferred to a non-original screen. 

Fast forward to the iPhone 11 and we had another level of complexity added to the screen’s integrated circuit. Apple screen IC manufactured by Texas Instruments, was designed with an upgrade now containing two memory chips. But there was something different about the second chip (within the IC adding another floor if using my previous building example), the second chip was a read only chip called a ROM (Read Only Memory). Unlike the memory chip used with the iPhone X for True Tone, this additional memory chip in the iPhone 11 screen IC was only readable and had no ability to be copied to another screen (even another original screen). 

In the iPhone 11 if you replaced one original screen for another you not only lost True Tone (as the code on that chip isn’t being confirmed as the original code programmed by Apple at factory), but you would also receive a message on the screen to advise that the iPhone could not verify if the screen is original. The message is misleading, because it’s not the screen it is not able to verify but the microchip on the screen. 

What was confusing about this new memory chip embedded inside the screen IC was that it’s only job was to communicate with the iPhone upon boot (when you turn on your iPhone) to verify if the microchip is present. It has no other purpose. We in the 3rd party repair industry took this as a direct jab at our market. For us at iCorrect, replacing a microchip is an everyday thing, but I couldn’t imagine how this would be for your local repairer. 

This use of ROM technology to display ‘non-genuine’ notifications and even disablements of features has been used in other parts in the iPhone. The battery from the iPhone XR upwards has a ROM inbuilt into the battery board, if not detected displays a non-genuine message but also disables the ability to read the battery health. We believe this level of pairing in the battery is combat poor quality batteries being sold and fitted into iPhones. (This is something we’ll cover in another blog).

Fast forward to the iPhone 12 & the rear camera unit has a ROM inbuilt which upon release gave a non-genuine notification & disabled camera features. Apple quickly U-turned the camera feature issue in an update but kept the non-genuine notification. The pairing of the rear camera is unfortunately something we’re unable to pinpoint and explain. We’re still researching this. As far as we understand there are no aftermarket or non-original rear cameras available.

Further forward to the present moment and the iPhone 13’s screen IC now not only acts as a ADC, enables True Tone, carries a ROM for the non-genuine message but also now communicates with Face ID. We believe this communication with Face ID is a bug in iOS15. But it shows us a glimpse of how much more complex the screen IC is going to be in the future. We expect the next generations of iPhone to contain 2 biometrics in Face ID & in screen Touch ID. 

We expect when replacing a screen in future will disable the in screen Touch ID. This is evident with Samsung who already have this feature in-built into some models. Apple and Samsung are working closely together in their smartphone screen technology, evident in their new iPhone 13 screen which uses a single flex cable to communicate with the iPhone. Something which we’ve seen in previous models of Samsung smartphones. (We’ll speak further about SPI communication in screen technology in the future regarding dual cable and single cable advancements). 

In my opinion, and something which I can’t comment on for the whole industry, is that this is not a fight with third party repair, this is Apple’s fight with China. We as consumers and repairers are just caught in the middle. Apple designs beautiful technology outside and in, they have it produced in China, who then disassemble the technology and manufacture alternative parts. Apple is using their own genius against the Chinese by blocking aftermarket parts. Unfortunately it also means that they also block the usage of their own parts. That genius by big tech manufacturers can be seen as control through serialisation of parts as discussed today. 

This move to disable Face ID was originally seen as a checkmate move by Apple, but today I’m happy to be reporting that this is only check. 

Moving the original screen IC from one original screen to another keeps the communication between the iPhone and the biometrics with perfect functionality of Face ID in iOS15. We do expect Apple to patch this bug in this communication between the microchips. We have video confirmation of this on our YouTube channel where you can find a longer explanation of our repair process and a look behind the scenes. 


by Ricky Panesar.