Hardware and Network Troubleshooting · Topic 5 of 7
Troubleshooting Mobile Devices
Diagnose common phone, tablet and laptop faults such as short battery life, swelling, cracked screens, poor wireless, overheating, slow apps and lockouts.
- 5 min
- A short battery life usually means a worn battery or heavy use.
- A swollen battery is dangerous; stop using it and replace it.
- Slow or failed charging often comes from the cable, charger or port.
What it is
Mobile devices fail in typical ways: the battery wears out, the screen breaks, the radios drop, the software slows or freezes. Many faults have simple fixes, such as a restart or a setting, while others need a part replaced.
Use the six step method: ask what changed, start with simple causes, fix, verify and record.
How it works
Battery and power
| Symptom | Likely causes and actions |
|---|---|
| Short battery life | Worn battery, heavy apps, bright screen, weak signal. Check battery health, lower brightness, close apps, replace an old battery |
| Not charging or charging slowly | Faulty cable or charger, dirty or damaged port, wrong charger. Try another cable and charger, and clean the port |
| Swollen battery | Failing lithium battery. Stop using it and replace it with care |
| Overheating | Heavy use, charging in a hot place, a failing battery, a blocked vent. Remove the case, stop heavy apps and let it cool |
A swollen battery can burst or catch fire. Do not charge or press it, and send it for safe recycling.
Screen and input
- Cracked screen: the glass or the panel is broken. Replace the screen. Use a protective case to prevent repeats.
- Dim display: check brightness, auto brightness and the backlight. A very faint image points to a hardware fault.
- Touch screen not responding: clean the screen, remove the cover or a protector, restart, then update. A fault in the digitizer needs a repair.
- Screen rotation or ghost touches: restart and check for water damage or screen damage.
- Keys or touchpad not working on a laptop: check for dirt or spills, check settings and test with an external keyboard.
- Cursor drift or inaccurate touch: touches land in the wrong place, or the pointer moves on its own. Recalibrate the touch screen in the settings, remove a screen protector, wipe off moisture or grease, restart and install updates. If it continues, the digitizer may be faulty.
- Stylus does not work: an active stylus has a battery or needs pairing, so charge or replace the battery and pair it again. Also check for a worn tip, a stylus that this device does not support, or a digitizer or driver fault.
Wireless and connectivity
| Symptom | Checks |
|---|---|
| No wireless connection | Airplane mode, Wi-Fi switch, correct network and password, router working, forget and rejoin the network, restart |
| Weak or intermittent Wi-Fi | Distance, interference, antenna wires on a laptop |
| Bluetooth not connecting | Bluetooth on, device in pairing mode, battery of the accessory, remove and pair again |
| No cellular data | Plan active, data enabled, roaming, subscriber identity module (SIM) seated, airplane mode off, network coverage |
| Global positioning system (GPS) not working | Location services off, no sky view, app permission missing |
| Cannot connect to an external display | Cable or adapter, wrong output setting, display input |
Software and performance
| Symptom | Likely causes and actions |
|---|---|
| Slow performance | Low storage, too many apps, outdated software, malware. Free space, close apps, update, restart |
| Apps not loading or crashing | App out of date, low storage, corrupt data. Update, clear cache, reinstall |
| Frozen system | Software hang. Force restart; update; reset if it keeps happening |
| No sound from speakers | Volume or mute, headphones or Bluetooth taking the audio, damaged speaker |
| Unable to decrypt email | Missing certificate or account profile, or wrong credentials. Check the account setup |
| System lockout | Too many wrong attempts on the passcode. Use the account recovery or an administrator tool |
A restart is the fastest first step for many software faults. Updates fix known bugs, while a factory reset is a last resort because it erases data, so back up first.
Physical and liquid damage
Liquid damage can cause random faults and corrosion. Power the device off at once, do not charge it and take it to be cleaned and checked. A drop may crack the screen or loosen internal connections.
Devices with sealed parts
Phones and tablets often need a repair shop or a part-swap kit. Laptops allow more component replacement, such as batteries, memory or storage. Follow the replacement technique from the earlier chapter.
When a phone suddenly has no network at all, check airplane mode and the SIM before blaming the carrier.
What to remember for the exam
- A short battery life usually means a worn battery or heavy use.
- A swollen battery is dangerous; stop using it and replace it.
- Slow or failed charging often comes from the cable, charger or port.
- A restart fixes many software faults; a factory reset is a last resort after a backup.
- No wireless connection: check airplane mode, then rejoin the network.
- Bluetooth failures: check pairing mode and pair again.
- Overheating can come from heavy apps, charging or a failing battery.
- A lockout needs account recovery or an administrator tool.
Common mistakes
Replacing the battery when the charger is at fault. Test the charger and cable first.
Charging a swollen battery. It is a fire risk.
Resetting before backing up. Data may be lost.
Forgetting airplane mode. It is a common cause of no signal.
Using a cheap, unapproved charger. It can charge slowly or damage the battery.
Check yourself
What should you do when a phone battery has swollen?
Stop using and charging it, and have it replaced and recycled safely.
A phone charges very slowly. What should you test first?
The cable, the charger and the charging port.
What is the usual first step for a frozen phone or app?
Restart the device, or force close the app.
Topic 5 of 7 in Hardware and Network Troubleshooting
Test yourself on Hardware and Network Troubleshooting
The full CompTIA A+ 220-1201 question bank has 856 questions, with timed practice exams and an explanation for every answer.
This study guide is independent and is not affiliated with, endorsed by, or sponsored by CompTIA. Vendor names, certification names and exam codes are trademarks of their respective owners and are used for identification only.