220-1101 Mobile Devices Practice Question
A user reports that their smartphone's 3.5mm headphone jack is not working. When headphones are inserted, the music continues to play from the built-in speaker, and the headphone icon does not appear in the status bar. The technician has cleaned the jack with compressed air and tested with multiple headphones. Which of the following components is MOST likely faulty?
⚠ Common exam trap
Watch out — candidates often assume a software or codec issue when the symptom is 'no detection,' but CompTIA tests the understanding that the mechanical detection switch inside the jack assembly is a separate failure point from the audio processing hardware.
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
✓
The headphone jack assembly.
The headphone jack assembly contains a mechanical switch that detects when a plug is inserted and routes audio away from the built-in speaker. Since cleaning and multiple headphones did not resolve the issue, the most likely fault is a broken or stuck detection mechanism within the jack assembly itself, preventing the device from recognizing that headphones are connected.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The audio codec chip.
Why it's wrong here
The audio codec chip performs digital-to-analog conversion and drives the headphone amplifier, but it does not contain the physical mechanism that senses when a plug is inserted. In modern phones, a separate mechanical switch or Hall-effect sensor inside the jack assembly sends a GPIO interrupt to the processor, which then shows the headphone icon and reroutes audio. If the codec were defective, you would still see the icon and hear nothing or distorted sound through the headphones; the phone would still detect the insertion. Since the problem is that the jack seems not to work at all, the codec is not the likely culprit.
- ✓
The headphone jack assembly.
Why this is correct
The headphone jack assembly is the only component that physically contains both the socket and the detection switch (or trigger for a Hall sensor) that tells the phone 'headphones are inserted.' When the 3.5mm plug is seated, it pushes a lever or magnet that toggles a switch, generating the signal that mutes the speaker and displays the headphone icon. If the assembly is damaged—for example, a broken solder joint, corroded contact, or clogged lint—the switch never actuates, so the phone behaves exactly as if no headphones were attached. The symptoms described point directly to this detection mechanism failing, making the jack assembly the correct first replacement part.
- ✗
The battery.
Why it's wrong here
The battery provides unregulated DC power to the phone's power management IC, and once that power is converted to the various system rails, it is distributed to all functional blocks including the headphone detection circuit. A failing battery typically causes the phone to shut down randomly, fail to power on, or show a low-battery warning—not to lose a single peripheral function while the rest of the phone operates normally. The headphone jack's detection switch draws negligible current and is fully powered as long as the phone is on. Therefore, the battery cannot be responsible for an isolated failure of headphone detection, and it should not be considered a likely cause.
- ✗
The motherboard.
Why it's wrong here
A motherboard failure could cause many issues, but the headphone jack is a separate assembly connected via a small board or flex cable; replacing the jack assembly is the logical first step before suspecting the mainboard.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 220-1101 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 220-1101 exam.