220-1101 Mobile Devices Practice Question
A user reports that their Android smartphone's touchscreen is unresponsive. The user performed a factory reset, but the problem persists. The technician notices that the screen has several deep scratches but no cracks. Which of the following is the MOST likely cause?
⚠ Common exam trap
It's easy for candidates to confuse a damaged LCD with a failed digitizer, assuming any screen damage affects both display and touch, but the exam tests the distinction that touch input is handled by the digitizer, not the LCD.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Failed digitizer
The digitizer is the component responsible for detecting touch input on a smartphone screen. Deep scratches can physically damage the digitizer's conductive layer, causing unresponsiveness even though the display (LCD) itself may still function. A factory reset cannot repair physical damage, so the problem persists, confirming a hardware failure in the digitizer.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Failed digitizer
Why this is correct
The digitizer is the capacitive touch layer bonded atop the LCD, typically a sheet of indium tin oxide (ITO). It detects finger contact by sensing changes in the screen's electrostatic field; deep scratches or cracks can sever the ITO's conductive traces, creating dead zones or total unresponsiveness. Because the user reports that the display itself still shows the home screen but touch does not respond, the failure is isolated to the digitizer, not the display panel. This is confirmed by the fact that visual output remains intact, while the touch input pathway is broken.
- ✗
Corrupted firmware
Why it's wrong here
Corrupted firmware is a software issue that would manifest as erratic behavior, boot loops, or unresponsive touch due to a buggy driver. A factory reset reinstalls the operating system and its display/touch drivers, which typically resolves such software-level corruption. If the touchscreen remains completely unresponsive after a factory reset, the root cause must be physical, not logical, ruling out firmware as the culprit. Therefore, choosing firmware fails to explain the persistence of the symptom across a software reset.
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Dead pixels
Why it's wrong here
Dead pixels are individual subpixels that fail to emit light, appearing as permanent black or colored dots on the screen. They are a defect of the liquid crystal display (LCD) panel, not the capacitive touch layer, and have no effect on the screen's ability to sense a finger. A touchscreen can be perfectly responsive even with several dead pixels scattered across the display. Since the user's complaint is that the touchscreen is unresponsive rather than that the image has spots, dead pixels are an incorrect diagnosis.
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Damaged LCD
Why it's wrong here
A damaged LCD—such as a cracked panel or leaked liquid crystal—typically presents with visible artifacts: discoloration, horizontal/vertical lines, or dark blotches. Even when the LCD is fractured, the capacitive touch layer can still register input, because the two are physically separate. The user's issue is limited to touch unresponsiveness without any reported display corruption, so LCD damage would not be the primary cause. Unlike a failed digitizer, which affects input only, LCD damage affects output only, making it an incorrect diagnosis.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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