Cell phones have become our closest companions. They wake us up, connect us, entertain us, and store our memories — so when a phone stops working, even a small fault can disrupt our entire routine. For repair technicians, understanding these issues is essential. For users, knowing the common problems helps you stay prepared and identify faults early.
“Every problem has a root cause — the real skill lies in finding it.”
This guide explains all major mobile phone faults, how they occur, what they mean, and how technicians typically diagnose them. The goal is to give you a clear, updated, and practical understanding of today’s smartphone issues — in simple language.
Types of Mobile Phone Faults
All phone problems fall into three broad categories:
1. Settings-Related Faults
These occur due to wrong configurations, disabled features, changed options, or simple mistakes made by the user.
2. Software Faults
These involve the phone’s operating system, apps, corrupt files, firmware crashes, or update failures.
3. Hardware Faults
These are physical failures such as broken displays, damaged charging ports, faulty motherboards, or non-working components.
Understanding which category the issue belongs to helps technicians diagnose faster and more accurately.
Full List of Modern Mobile Phone Faults (Updated)
Below is an expanded and updated list of all common smartphone faults, including newly emerging issues found in today’s touchscreen devices.
Obsolete or outdated faults (from keypad-era phones) have been removed, updated, or rewritten.
1. Dead Phone (Not Powering On)
A phone that doesn’t turn on, doesn’t vibrate, and shows no charging sign is considered dead.
Causes may include:
- Battery failure
- Water damage
- Short circuit
- Faulty power IC (PMIC)
- Damaged charging port
Technicians diagnose this using power supply tools and multimeters.
2. SIM Card Not Detected
The phone shows “No SIM” or “Insert SIM Card” even when the SIM is inserted.
Usually caused by:
- Dirty or bent SIM pins
- Damaged SIM slot
- Software conflict
- Network IC failure
Modern eSIM phones may show activation issues instead.
3. Hanging / Freezing / Lagging
The cell phone becomes unresponsive or slow.
Causes include:
- Low storage
- Heavy apps
- Overheating
- Corrupted firmware
- Faulty RAM or CPU chip
A common sign of deeper software damage.
4. Network Issues (No Signal / Low Signal / Dropping Calls)
This includes:
- No network
- Weak signal
- “Emergency calls only”
- Calls dropping automatically
Reasons:
- Damaged antenna
- SIM issues
- Firmware bugs
- Network IC failure
5. Microphone Not Working
People cannot hear you during calls or voice recordings.
Common reasons:
- Dust in MIC hole
- Water damage
- Damaged MIC module
- Firmware glitch
- Noise cancellation mic fault
Modern phones have multiple microphones, so diagnosis requires precision.
6. Speaker Issues (No Sound During Calls)
The earpiece speaker stops working, making you unable to hear the caller.
Usually caused by:
- Dust buildup
- Flex cable damage
- Moisture
- Faulty earpiece speaker
7. Loudspeaker / Media Speaker Fault
No ringtone, music, notifications, or hands-free audio.
Reasons:
- Faulty loudspeaker unit
- Software audio routing issue
- Audio IC failure
8. Vibration Not Working
Vibration motor (haptic motor) stops functioning.
Common causes:
- Motor wear-out
- Loose connection
- Board damage
9. Display / Screen Faults
This includes:
- Blank screen
- Broken or cracked display
- Flickering issue
- Green/pink lines
- Black spots
- No backlight
- Touch working but no display
- Display working but touch not responding
Modern OLED screens also face:
- Burn-in
- Ghosting
- Color shifts
10. Auto Power Off
Phone switches off randomly without user action.
Reasons:
- Overheating
- Battery failure
- Power IC malfunction
- Corrupt firmware
11. Auto Restart (Bootloop)
The phone continuously restarts or gets stuck on the logo.
Causes:
- System update failure
- Damaged OS
- Application conflict
- Hardware shorting
- Damaged booting IC
Bootloops are common after failed software updates.
12. Call Drops / Call Disconnecting
The call ends abruptly.
This may be due to:
- Weak network
- Software bugs
- Damaged antenna
- Faulty baseband IC
13. Charging Problems
One of the most common faults today. Includes:
- Not charging
- Slow charging
- Intermittent charging
- Overheating while charging
- Charger connected but not increasing battery percentage
Reasons:
- Faulty cable or adapter
- Broken charging port
- Charging IC damage
- Battery swelling
- Dirt inside port
14. Charging Port Damage (USB Port Faults)
When the port becomes loose, bent, corroded, or physically damaged.
Symptoms:
- Cable must be held at an angle
- Charging stops when moved
- No data transfer
15. Touchscreen Problems
Touch issues are very common today.
Includes:
- Touch not working
- Touch responding on its own (ghost touch)
- Slow or delayed touch
- Touch working only in some areas
Causes:
- Damaged touch panel
- Faulty display connector
- Software glitch
16. Battery Draining Fast
Battery percentage drops quickly even with light usage.
Reasons:
- Battery health degraded
- Power-hungry apps
- Background processes
- Network fluctuations
- Faulty charging IC
- Swollen battery
Technicians use software and multimeter tools to confirm battery health.
17. Overheating Problems
Phone becomes hot during use, charging, or even idle.
Causes:
- Heavy gaming
- Faulty CPU
- Short circuit
- Damaged battery
- Poor ventilation
- Malware apps
If the phone overheats too much, it may shut down automatically.
18. Bluetooth Not Working
Bluetooth won’t connect, keeps disconnecting, or doesn’t turn on.
Reasons:
- Corrupted Bluetooth firmware
- Radio frequency interference
- Damaged Wi-Fi/Bluetooth IC
19. Wi-Fi Not Connecting
Wi-Fi may show:
- No connection
- Authentication error
- Frequent disconnection
Possible causes:
- Router conflict
- Software bugs
- Wi-Fi IC damage
20. Mobile Data Not Working
Internet does not work even though network bars are visible.
Causes include:
- APN settings wrong
- Corrupt OS
- Network provider issue
- Baseband malfunction
21. Camera Problems
Modern camera modules face several faults:
- Camera not opening
- “Camera failed” error
- Blurry pictures
- Black screen when switching lenses
- Ultrawide/macro lens not detecting
- Front camera not working
- Portrait mode failure
- Video stabilization not working
Some premium phones also face OIS motor failure.
22. Fingerprint Sensor Not Working
Includes:
- No fingerprint detection
- Slow recognition
- Error in setup
- In-display fingerprint failure
Usually caused by:
- Damaged sensor
- Moisture
- Software conflicts
23. Face Unlock Not Working
Face ID or Face Unlock may stop working due to:
- Dirty front camera
- Low light
- Damaged sensors
- Software update issues
- TrueDepth camera failure (iPhone)
24. Memory Card Not Detected
For phones with SD card slots.
Reasons:
- Corrupted SD card
- Dirty contacts
- Damaged slot
- Unsupported file format
25. Proximity Sensor Issue
Screen does not turn off during calls or turns off at the wrong time.
Causes:
- Screen guard blocking sensor
- Sensor misalignment
- Calibration error
26. GPS / Location Problems
Navigation becomes inaccurate or fails to track position.
Reasons:
- Weak GPS antenna
- Software bugs
- Location services turned off
- Corrupted system files
27. App Crashing / App Not Opening
Apps force-close due to:
- Outdated version
- Low RAM
- OS conflict
- Corrupted data
28. Storage Full Even When Not Used
A common issue in modern phones.
Reasons:
- System cache
- Duplicate files
- Hidden media
- Malware apps
- Defective memory chip (EMMC/UFS)
Technicians check using special memory analysis tools.
29. Phone Not Detecting on Computer (USB Data Failure)
Includes:
- PC not recognizing phone
- No file transfer
- Only charging but no MTP mode
Reasons:
- Faulty USB driver
- Cable issues
- Data pins damaged
- Motherboard fault
30. Notification Problems
User does not receive notifications on time.
Occurs due to:
- Battery optimization restrictions
- Disabled app permissions
- Software bugs
31. Liquid Damage Faults
Water damage causes unpredictable issues such as:
- Touch not working
- Speaker distortion
- Charging short
- No power
- Corrosion on connectors
Liquid damage requires deep cleaning and board-level diagnosis.
32. Software Update Issues
Phones may face:
- Update stuck
- Update failure
- Feature missing
- Battery draining after update
Some updates introduce bugs that require patch fixes.
33. Bootloader / FRP / Account Lock Issues
Phones sometimes get locked due to:
- Forgot password
- Factory reset protection (FRP)
- Carrier lock
- Bootloader relocking
Technicians use specialized software tools to resolve these cases (lawfully).
34. Audio IC Failure (Common in Certain Models)
Symptoms:
- No sound
- Voice not recorded
- Speaker disabled
- Microphone not detecting
- Call drops when enabling loudspeaker
This is a common board-level hardware problem.
35. Backlight Failure
Screen is ON but completely dark unless viewed under direct light.
Causes include:
- LED backlight strip damage
- Backlight driver IC failure
- Blown backlight filter
Learn how to troubleshoot the most common cell phone faults by reading How To Repair Your Cell Phone Yourself
Conclusion
Mobile phones may look simple from the outside, but they contain hundreds of delicate components inside. Knowing the different types of faults helps technicians diagnose issues faster and gives users a better understanding of what might be wrong with their device.
“A fault diagnosed well is already half repaired.”
If you want to learn how to fix many of these problems yourself, always start with simple checks before attempting advanced repairs.