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A+ Core 1 · CompTIA 220-1201 V15 · Objective 5.5

Given a scenario, troubleshoot common mobile device issues

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Objective 5.5: Given a scenario, troubleshoot common mobile device issues

Cert: CompTIA A+ Core 1 (220-1201) V15 Domain: 5.0 Hardware and Network Troubleshooting Weight: ~28% of Core 1 (largest domain) Depth: Given a scenario, troubleshoot. Recognize the common mobile device problems and apply remediation.

What this objective tests

You should recognize the typical mobile device symptoms (battery, screen, charging, connectivity, environmental damage, calibration) and apply the right diagnostic and remediation steps. This pairs with 1.1 (mobile device hardware).

Key facts

Common symptoms and their causes:

  • Poor battery health. Battery capacity drops with age and cycle count. Battery health report (iPhone Settings, Android Battery Care, Windows powercfg /batteryreport) shows current vs design capacity.
  • Swollen battery. Lithium battery has expanded inside the device, pushing the case or display outward. Safety hazard. Stop using the device, do not charge, dispose of the battery properly.
  • Broken screen. Cracked glass, panel damage, or both. Touch may still work. Replace the screen assembly (or send to authorized repair if biometric features need preservation).
  • Improper charging. Phone or laptop charges slowly, intermittently, or not at all. Could be the cable, the charger, the port (lint inside is common on phones), the battery, or the charging IC inside the device.
  • Poor/no connectivity. Wi-Fi, cellular, or Bluetooth not working. Toggle airplane mode, restart, forget and rejoin network, check for SIM/eSIM issues for cellular.
  • Liquid damage. Water or other liquid in the device. Power off immediately, do not charge, dry as much as possible (rice does NOT help; warm dry air or a desiccant does). Send for professional repair.
  • Overheating. Phone or laptop running hot. Causes: heavy app load, charging while in use, blocked vents, environment (car dashboard in summer), failing battery.
  • Digitizer issues. Touchscreen not registering touch (or registering touches in wrong places). Display works fine. Replace digitizer.
  • Physically damaged ports. Bent USB-C, Lightning, or USB-A. May charge intermittently or not at all. Inspect for debris first (lint in phone ports is extremely common), then check for visible damage.
  • Malware. On Android in particular, sideloaded malicious apps can drain battery, pop up ads, send SMS, or steal data. iOS is much more locked down but social engineering is still a path.
  • Cursor drift / touch calibration. Trackpad or touchscreen registers touches that did not happen, or in the wrong location. Often calibration drift; sometimes a failing component.
  • Unable to install new applications. Storage full, OS too old for the app's minimum requirement, MDM policy blocking installs, regional app store restrictions.
  • Stylus does not work. Battery dead (active styluses), Bluetooth not paired, software setting disabled, or hardware failure.
  • Degraded performance. App over-installation, storage full, malware, aging battery causing CPU throttling, OS upgrade tax.

Diagnostic approach

  1. Power cycle the device. Solves a surprising fraction of mobile complaints.
  2. Update OS and apps. Bug fixes resolve a lot.
  3. Test in safe mode (Android) or check for misbehaving apps.
  4. Check battery health and storage capacity.
  5. Try a different cable/charger for charging issues.
  6. Inspect ports for debris and damage.
  7. Reset network settings for connectivity issues that persist.
  8. For persistent issues, back up and factory reset.

Common gotchas

  • Lint in the Lightning/USB-C port. Looks like charging is failing but it's just compacted lint. Clean carefully with a wooden toothpick (never metal).
  • Don't use rice on liquid damage. Old wisdom that does not work. Rice doesn't absorb meaningful moisture and can leave starch inside the device. Silica gel desiccant or a dedicated drying service is the right approach.
  • Cheap third-party chargers. Can damage the device's charging IC or battery. Stick to reputable chargers, especially for high-wattage USB-C PD.
  • Biometric loss after screen replacement. Third-party screen swaps can lose Face ID/face unlock if the IR sensor is not transferred or recalibrated.
  • MDM blocking app installs. Corporate-managed devices may block app store installs entirely. Users see vague errors; check MDM policy.
  • Carrier locked. A phone may refuse a new SIM because it's locked to the original carrier.
  • Swollen battery dismissed. Customers sometimes report a "puffy" laptop or phone as cosmetic. It is a safety hazard.

Real-world context

Common helpdesk patterns:

  • "My phone is hot and the battery dies fast." Check battery health, check for runaway apps, check that the phone isn't sitting in direct sun. Replace battery if degraded.
  • "My laptop won't charge." Check cable, charger, port. Try a different known-good charger. If the issue persists, internal charging IC or battery may need service.
  • "My touchscreen stopped responding but the screen looks fine." Digitizer failure. Screen and digitizer are separate even though they look like one component.
  • "I can't install our company app." MDM policy block, regional restriction, OS too old, or storage full.

Sources

  • [CompTIA A+ 220-1201 Exam Objectives Version 4.0, Section 5.4](../../../../../../30-RevyTechJourney/CompTIA%20A%2B%20220-1201%20Exam%20Objectives%20%284.0%29.pdf)
  • [Wikipedia: Lithium-ion battery](https://en.wikipedia.org/wiki/Lithium-ion_battery)
  • [Wikipedia: Touchscreen](https://en.wikipedia.org/wiki/Touchscreen)
  • [Wikipedia: Mobile device forensics](https://en.wikipedia.org/wiki/Mobile_device_forensics)
  • [Apple Support: iPhone battery and performance](https://support.apple.com/en-us/HT208387)