CompTIA A+ (220-1201): Hardware and Network Troubleshooting
Table of Contents
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Hardware and Network Troubleshooting is 28% of the CompTIA A+ 220-1201 Core 1 exam, the largest domain on either exam. This module covers the troubleshooting methodology and how to diagnose hardware, displays, mobile devices, printers, and networks. The exam tests process as much as parts, so learn the methodology in order.
Troubleshooting is the skill that defines a good technician. You follow a repeatable process, read the symptoms, form a theory, and prove it before you replace anything. This module turns scattered symptoms into a reliable diagnosis.
The CompTIA Troubleshooting Methodology
You follow these steps in order on every problem. The exam expects this exact sequence.
- Identify the problem. Gather information, question the user, and back up data before changes.
- Establish a theory of probable cause. Question the obvious.
- Test the theory to confirm it. If it fails, form a new theory or escalate.
- Establish a plan of action and identify potential effects.
- Implement the solution or escalate as needed.
- Verify full functionality and apply preventive measures.
- Document findings, actions, and outcomes.
Motherboard, RAM, CPU, and Power Issues
You read the symptoms of core component failure.
| Symptom | Likely cause |
|---|---|
| POST beep codes | RAM, GPU, or CPU not detected |
| No power, no fans | Dead PSU or wall power |
| Random shutdowns | Overheating or failing PSU |
| Burning smell | Failed PSU or component |
| Swollen capacitors | Failing motherboard |
| Continuous reboots | RAM, overheating, or corrupt firmware |
Overheating often traces to dust, failed fans, or dried thermal paste.
Drive and RAID Issues
You catch storage failure before data is lost.
- Grinding or clicking noises signal a failing mechanical HDD. Back up immediately.
- S.M.A.R.T. failures warn that a drive is degrading.
- RAID not found points to a failed controller or member drive.
- Slow read/write suggests a dying drive or full disk.
- Bootable device not found means a missing or failed boot drive.
Display and Video Issues
You diagnose what the user sees on screen.
| Symptom | Cause |
|---|---|
| Dead pixels | Failed individual pixels |
| Burn-in | Static image ghosted on OLED |
| Dim image | Failing backlight or inverter |
| Flickering | Loose cable or failing panel |
| Distorted geometry | Wrong resolution or failing GPU |
| No image, power on | Cable, input source, or GPU |
Mobile Device Hardware Issues
You handle the special risks of sealed devices.
- A swollen battery is a fire hazard. Stop using the device and replace it.
- Cracked screens need digitizer and panel replacement.
- Liquid damage calls for power-off and professional cleaning.
- Poor battery life can mean a worn battery or a rogue app.
- Overheating points to heavy load, a failing battery, or a charging fault.
Network Issues
You isolate connectivity problems from the device outward.
| Symptom | Likely cause |
|---|---|
| No connectivity | Cable, NIC, or DHCP failure |
| Intermittent drops | Loose cable or wireless interference |
| Slow speeds | Congestion, bad cable, or duplex mismatch |
| High latency/jitter | Congestion or weak signal |
| APIPA address (169.254.x.x) | DHCP server unreachable |
| Limited connectivity | Wrong IP, gateway, or DNS |
Build the underlying knowledge in Networking Fundamentals .
Printer Issues
You resolve the common print faults.
- Paper jams trace to worn rollers, wrong paper, or debris.
- Faded prints mean low toner or ink.
- Ghosting points to a failing drum or fuser.
- Garbled output means a wrong or corrupt driver.
- No connectivity points to network, queue, or spooler problems.
Next Steps
You have now finished all five Core 1 domains. Move into Core 2 with Operating Systems , then Software Troubleshooting for the software side of diagnostics. Review Hardware Components and Mobile Devices . Return to the CompTIA A+ Course .
