220-1101 Mobile Devices Practice Question
After a user updates their iPhone to the latest iOS version, the device can no longer connect to the cellular network. The SIM card is recognized, Wi-Fi works, and the phone can make calls over Wi-Fi (VoWiFi). The technician performed a network settings reset and a full restore from a backup, but the issue persists. Which of the following is the MOST likely cause?
⚠ Common exam trap
CompTIA often tests the distinction between software/firmware corruption and hardware failure by presenting a scenario where a full restore fails to fix a radio issue, leading candidates to incorrectly choose 'baseband firmware corruption' (Option B) instead of recognizing that a persistent hardware fault is the root cause.
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 iPhone's baseband hardware has failed
The symptoms—SIM recognized, Wi-Fi and VoWiFi working, but no cellular connectivity after an iOS update—point to a hardware-level baseband failure. The baseband processor handles cellular radio functions; an update cannot corrupt hardware, but it can expose a pre-existing latent hardware fault. Since a network settings reset and full restore from backup did not resolve the issue, the problem is not software or firmware, leaving physical baseband hardware failure as the most likely cause.
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 SIM card is damaged or locked to a different carrier
Why it's wrong here
A damaged or carrier-locked SIM would cause the iPhone to display an error like 'Invalid SIM' or 'No SIM' and would also prevent VoWiFi from authenticating over the carrier's IP network. Because the SIM is still recognized and the user can place VoWiFi calls, the SIM card's identity and carrier provisioning are functioning normally. The loss of cellular signal stems from a different layer—specifically the device's RF and modem subsystem—rather than the SIM itself.
- ✗
The iOS baseband firmware is corrupted
Why it's wrong here
Baseband firmware corruption typically manifests as a 'No Baseband' call screen or a baseband crash loop, and it can be completely reflashed using a DFU restore, which reinstalls the baseband firmware alongside iOS. If the cellular issue persists even after a full restore from the latest IPSW, the firmware itself is not at fault; the baseband hardware is unable to execute or utilize it. The fact that the SIM is still detected and Wi-Fi works suggests the baseband processor may boot, but its cellular radio functionality is visibly dead.
- ✓
The iPhone's baseband hardware has failed
Why this is correct
The iPhone's baseband hardware (the modem chip) is solely responsible for cellular RF transmission and reception. A failure here means the device can still read the SIM and use Wi-Fi, because those functions do not require the RF transceiver to be operational, but it cannot register with any carrier. The iOS update likely triggered an existing latent fault or a power event that killed the modem, and a full software restore cannot repair physical damage. This is a classic hardware failure scenario, distinct from software or SIM-related issues.
- ✗
The iOS update introduced a compatibility issue with the carrier
Why it's wrong here
A carrier compatibility issue introduced by an iOS update is typically tied to carrier bundle settings, which can be reset by restoring the device and reapplying the carrier update from Apple's servers. Since the user's problem remains after a full restore (which rebuilds all configuration profiles), a software incompatibility is very unlikely. Moreover, carrier compatibility problems usually lead to partial service loss or feature-specific glitches, not a complete absence of cellular service while VoWiFi continues to work, which points to the modem hardware as the root cause.
When this WOULD be correct
This would be correct if the question stated that the problem occurred immediately after an iOS update on multiple devices of the same model, and a restore from backup did not fix it, but a clean install (without restoring backup) resolved the issue, indicating a software compatibility bug specific to that iOS version and carrier combination.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 220-1101 exam frequently reuses these exact scenarios with slightly different constraints.
✓The iPhone's baseband hardware has failedCorrect answer▾
Why this is correct
The iPhone's baseband hardware (the modem chip) is solely responsible for cellular RF transmission and reception. A failure here means the device can still read the SIM and use Wi-Fi, because those functions do not require the RF transceiver to be operational, but it cannot register with any carrier. The iOS update likely triggered an existing latent fault or a power event that killed the modem, and a full software restore cannot repair physical damage. This is a classic hardware failure scenario, distinct from software or SIM-related issues.
✗The iOS update introduced a compatibility issue with the carrierWrong answer — click to see why▾
Why this is wrong here
The issue persists after a full restore from backup, which would reinstall the iOS system and eliminate software-based compatibility issues. A compatibility issue would typically be resolved by a restore or update, not persist.
★ When this WOULD be the correct answer
This would be correct if the question stated that the problem occurred immediately after an iOS update on multiple devices of the same model, and a restore from backup did not fix it, but a clean install (without restoring backup) resolved the issue, indicating a software compatibility bug specific to that iOS version and carrier combination.
Why candidates choose this
Candidates may think that iOS updates can introduce bugs that affect carrier compatibility, especially when the issue appears right after an update and other functions (Wi-Fi, VoWiFi) work, suggesting a software-level problem rather than hardware failure.
Analysis generated from the official 220-1101blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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JA
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.