Overview
Hardware and Network Troubleshooting is Core 1 (220-1201) domain 5.0 and carries 28% of that exam across six objectives: troubleshooting motherboards, RAM, CPUs and power; drives and RAID; video, projector and display issues; common mobile device issues; network issues; and printer issues. The Core 1 objectives frame the domain with CompTIA's troubleshooting methodology: identify the problem, establish a theory of probable cause, test the theory, establish a plan and implement the solution, verify full functionality and add preventive measures, then document findings.
Candidates must read a symptom such as a clicking drive, a 169.254.x.x address, a ghosted print or a swollen battery and choose the most probable cause or the safest next action. This domain is the practical payoff of Core 1 domains 1.0 through 3.0, and its method carries into Core 2 domain 3.0 software troubleshooting.
How it's tested
Most items present a symptom and ask for the most likely cause, the FIRST or NEXT step, or the BEST fix. The answer depends on matching the exact symptom wording to a component and respecting the methodology's order. Distractors are often valid repairs that skip a step, such as replacing hardware before testing the theory or before backing up data.
-
Symptom to cause
A specific sign such as a wrong system clock, grinding noise, vertical lines on prints or jitter on calls points to one component or condition.
-
Next step in the method
A partial troubleshooting story is told and you choose what comes next, such as testing the theory, escalating, or verifying full functionality.
-
Safest effective action
Several fixes would work, and you choose the one that protects data, people and equipment first, such as backing up a failing drive or powering down at a burning smell.
A user reports the PC's clock resets to an old date after every shutdown, and the system sometimes warns about BIOS settings at startup. Both symptoms point to lost CMOS settings when mains power is removed, which is the classic sign of a depleted CMOS battery. Replacing the coin-cell battery and re-entering firmware settings is the fix, not resyncing NTP or reinstalling the operating system.
Objectives 6
Official objectives from the CompTIA outline, in outline order.
5.1 Given a scenario, troubleshoot motherboards, RAM, CPUs, and powerPOST failures, crashes, overheating, power faults and physical warning signs.
- What it means
- Covers symptoms such as POST beeps, proprietary crash screens (Windows stop screen, macOS spinning wheel), blank screen, no power, sluggish performance, overheating, burning smell, random shutdowns, application crashes, unusual noise, swollen capacitors and inaccurate system date and time.
- What to understand
- Beep codes are vendor-specific and point to memory, video or CPU faults before the OS loads. Overheating causes throttling and random shutdowns, so check fans, dust, airflow and thermal paste. A burning smell or bulging capacitors means power down and replace the part. A clock that resets after power-off indicates a failing CMOS battery.
- How it shows up
- A PC shuts down after twenty minutes of load, or beeps with a blank screen after a memory upgrade, and you choose the most likely cause.
- Common confusion
- Treating random shutdowns as a software issue. Shutdowns under load usually point to heat or an inadequate power supply, while a stop screen with a memory-related error points to RAM.
5.2 Given a scenario, troubleshoot drive and RAID issuesFailing drives, boot device errors, S.M.A.R.T. warnings and degraded arrays.
- What it means
- Covers LED status indicators, grinding and clicking noises, audible alarms, bootable device not found, data loss or corruption, S.M.A.R.T. failure, extended read/write times, low IOPS, missing drives in the OS, RAID failure and a missing array.
- What to understand
- Clicking or grinding from a hard drive and S.M.A.R.T. warnings both predict imminent failure, so back up data immediately before anything else. Bootable device not found can mean wrong boot order, a disconnected cable, a removed USB stick confusing boot order, or a dead drive. A degraded RAID with an alarm needs the failed member replaced and the array rebuilt; a missing array suggests a controller or configuration fault.
- How it shows up
- A drive clicks and the OS reports S.M.A.R.T. errors, or a server's array LED turns amber, and you choose the first action.
- Common confusion
- Running chkdsk or defragmentation on a physically failing drive. Extra disk activity can finish off a dying drive; copy the data off first.
5.3 Given a scenario, troubleshoot video, projector, and display issuesInput source, cabling, bulbs, image quality, burn-in, dead pixels and sizing.
- What it means
- Covers incorrect input source, physical cabling issues, a burned-out projector bulb, fuzzy, dim, distorted or flashing images, display burn-in, dead pixels, incorrect color display, audio issues, image sizing problems and intermittent projector shutdown.
- What to understand
- Start with the obvious: input source, cable seating and the correct port. Fuzzy text often means a non-native resolution. A dim laptop image can be brightness settings or a failing backlight. Projectors that shut off intermittently are usually overheating from blocked vents or dirty filters. Burn-in is permanent image retention, while dead pixels stay one color.
- How it shows up
- A presenter connects a laptop and the projector shows no signal, or a monitor shows blurry text after a new install, and you pick the first check.
- Common confusion
- Replacing a projector bulb when the projector shuts down intermittently. Intermittent shutdowns point to heat and airflow; a dead bulb gives no image at all.
5.4 Given a scenario, troubleshoot common mobile device issuesBattery, charging, screen, connectivity, liquid damage, overheating and app faults on mobile hardware.
- What it means
- Covers poor battery health, swollen battery, broken screen, improper charging, poor or no connectivity, liquid damage, overheating, digitizer issues, physically damaged ports, malware, cursor drift or touch calibration, inability to install apps, stylus not working and degraded performance.
- What to understand
- A swollen lithium-ion battery is a fire risk: stop using and charging the device, do not puncture or press it, and replace and dispose of it properly. Improper charging usually traces to the cable, adapter, or a dirty or damaged port before the battery. Ghost touches or drift point to the digitizer or calibration. Liquid damage needs immediate power-off.
- How it shows up
- A laptop's touchpad lifts or the case bulges, or a phone charges only at a certain cable angle, and you choose the safe and likely fix.
- Common confusion
- Treating a swollen battery as a performance issue to recalibrate. It is a safety hazard requiring removal from service.
5.5 Given a scenario, troubleshoot network issuesIntermittent and limited connectivity, slow speeds, latency, jitter, port flapping and interference.
- What it means
- Covers intermittent wireless connectivity, slow network speeds, limited connectivity, jitter, poor Voice over IP (VoIP) quality, port flapping, high latency, external interference, authentication failures and intermittent internet connectivity.
- What to understand
- Limited connectivity with an APIPA address points to DHCP. Jitter is variation in delay and degrades VoIP and video even when bandwidth is fine. Port flapping is a switch interface repeatedly going up and down, typically from a bad cable, connector, NIC or duplex mismatch. Interference from microwaves, cordless devices or neighboring networks degrades 2.4 GHz Wi-Fi.
- How it shows up
- Calls break up while downloads look normal, or a switch log shows one port bouncing, and you identify the cause and tool.
- Common confusion
- Equating slow speed, latency and jitter. Bandwidth is capacity, latency is delay, and jitter is inconsistency in that delay.
5.6 Given a scenario, troubleshoot printer issuesPrint defects, feed problems, queue issues, connectivity and finishing faults.
- What it means
- Covers lines down printed pages, garbled print, faded prints, speckling, double or echo images, paper jams, paper not feeding, multipage misfeed, incorrect paper orientation, multiple jobs pending, frozen print queue, tray not recognized, connectivity issues, grinding noise and finishing issues such as staple jams and hole punch faults.
- What to understand
- Garbled characters point to the wrong driver; a frozen queue is fixed by clearing jobs and restarting the Print Spooler service. On laser printers, toner that smears or rubs off points to the fuser, while repeating marks or echo images point to the drum or imaging unit. Multipage misfeeds come from worn separation pads or humid paper. Faded output means low toner or ink or an economy setting.
- How it shows up
- Every page shows the same vertical line, or jobs sit in the queue and nothing prints, and you choose the component or service.
- Common confusion
- Replacing toner when prints smear. Toner that is not bonded to the page is a fusing problem, not a toner shortage.
High-yield concepts
The terms, rules and formulas this domain turns into questions most often.
-
Troubleshooting methodology
Identify the problem, establish a theory of probable cause, test the theory, establish a plan of action and implement it, verify full functionality and add preventive measures, document findings.
- Remember
- Back up data before making changes during identification, and escalate if a tested theory is not confirmed and no new theory can be formed.
- Tested as
- Drives FIRST and NEXT questions across both cores.
- Trap
- Implementing a fix before the theory has been tested, or closing the ticket before verifying full system functionality.
-
Question the obvious
When forming a theory, check simple causes first: power, cables, input source, settings and recent changes.
- Remember
- Many scenarios are solved by a loose cable, wrong input or disabled adapter, and the exam rewards checking these before replacing parts.
- Tested as
- Display, network and printer first-step questions.
- Trap
- Choosing an expensive replacement as the first action.
-
POST beep codes
Audible codes generated by firmware when power-on self-test finds a fault before video initializes.
- Remember
- Codes vary by firmware vendor, so look them up in the motherboard documentation.
- Tested as
- No display after power-on, especially after a memory or video change.
- Trap
- Assuming one universal meaning for a beep pattern.
-
CMOS battery failure
The coin-cell battery that keeps the real-time clock and some firmware settings when the PC is unplugged.
- Remember
- Its classic symptom is an incorrect date and time after power is removed, sometimes with settings reset warnings.
- Tested as
- Inaccurate system date and time is listed in objective 5.1.
- Trap
- Fixing it with time sync or an OS reinstall.
-
Overheating
Excess temperature that causes throttling, sluggish performance and protective shutdowns.
- Remember
- Check fans, dust, blocked vents, ambient temperature and thermal paste; firmware temperature monitoring confirms it.
- Tested as
- Random shutdowns under load or loud fans.
- Trap
- Replacing the power supply first when heat is the cause.
-
Swollen capacitors and burning smell
Physical signs of failing power components or electrical damage.
- Remember
- Power down immediately and replace the affected part; do not keep running the system.
- Tested as
- Safety-first questions in objective 5.1.
- Trap
- Continuing to troubleshoot with power applied.
-
S.M.A.R.T.
Self-Monitoring, Analysis and Reporting Technology built into drives to predict failure from metrics such as reallocated sectors.
- Remember
- A S.M.A.R.T. warning means back up now and plan replacement.
- Tested as
- Drive health scenarios.
- Trap
- Running intensive disk repair before securing the data.
-
Degraded RAID
An array running with a failed member, still serving data but with reduced or no remaining fault tolerance.
- Remember
- Replace the failed drive and let the array rebuild; verify backups because a second failure may destroy the array.
- Tested as
- Audible alarms or amber drive LEDs on servers.
- Trap
- Reinitializing or recreating the array, which erases it.
-
Native resolution
The exact pixel grid of an LCD or OLED panel.
- Remember
- Running a different resolution causes fuzzy text and sizing problems.
- Tested as
- Blurry display after driver or monitor changes.
- Trap
- Replacing the monitor or cable for a settings issue.
-
Swollen battery
A lithium-ion battery expanding from gas buildup due to age, heat or damage.
- Remember
- Stop use and charging, do not puncture it, replace it and recycle it according to local regulations.
- Tested as
- Mobile safety scenarios, such as a lifted touchpad or bulging case.
- Trap
- Recalibrating the battery or continuing to charge it.
-
Jitter
Variation in packet delay over time.
- Remember
- High jitter causes choppy VoIP and video even when bandwidth and average latency look acceptable.
- Tested as
- Poor call quality scenarios.
- Trap
- Buying more bandwidth to fix a jitter problem.
-
Port flapping
A switch port repeatedly transitioning between up and down.
- Remember
- Common causes are a damaged cable or connector, a failing NIC or switch port, or a speed or duplex mismatch.
- Tested as
- Intermittent wired connectivity questions.
- Trap
- Reconfiguring IP settings when the physical link is unstable.
-
Fuser vs. drum faults
In laser printers the fuser bonds toner with heat and pressure; the drum or imaging unit forms the image.
- Remember
- Smearing toner points to the fuser, while repeating marks, lines down the page or echo images point to the drum or imaging unit.
- Tested as
- Print defect questions.
- Trap
- Replacing toner for a fusing problem.
-
Print Spooler
The Windows service that queues and sends print jobs.
- Remember
- A frozen queue is cleared by stopping the spooler, deleting stuck jobs and restarting it.
- Tested as
- Multiple jobs pending or frozen queue scenarios.
- Trap
- Reinstalling the printer before clearing the spooler.
Side by side
Concepts candidates mix up, compared on the point that decides the answer.
Bandwidth vs. latency vs. jitter
| Concept | Meaning | Key difference | Common trap |
|---|---|---|---|
| Bandwidth | How much data a link can carry per second. | Capacity; affects large transfers. | Upgrading it to fix delay-sensitive call problems. |
| Latency | Time for a packet to travel from source to destination. | Delay; affects responsiveness and remote sessions. | Ignoring it on satellite links. |
| Jitter | Variation in latency between packets. | Inconsistency; affects VoIP and video quality. | Assuming good average latency rules it out. |
Laser defect: fuser vs. drum vs. toner
| Concept | Meaning | Key difference | Common trap |
|---|---|---|---|
| Fuser | Heated rollers that melt toner onto paper. | Toner smears or rubs off; possible echo from a damaged roller. | Replacing the toner cartridge. |
| Drum or imaging unit | Photosensitive drum that holds the image before transfer. | Repeating marks, lines down the page or echo images. | Cleaning the fuser for a drum scratch. |
| Toner | The powder that forms the printed image. | Faded output or blank areas when low; speckling if leaking. | Blaming it for smearing. |
Failing drive vs. boot configuration vs. RAID controller
| Concept | Meaning | Key difference | Common trap |
|---|---|---|---|
| Failing drive | Mechanical or flash wear in a single drive. | Clicking, grinding, S.M.A.R.T. warnings, slow reads. | Running heavy repair utilities before backing up. |
| Boot configuration | Firmware boot order or missing boot loader. | Bootable device not found with a healthy drive visible in firmware. | Replacing a working drive. |
| RAID controller or configuration | The adapter or settings managing the array. | Missing array with drives otherwise healthy. | Recreating the array and wiping the data. |
Exam traps
Each trap is an answer that looks right. Learn the clue that should change your mind.
-
Fix before test
- What candidates pick
- Order a new motherboard as soon as the theory of a failed board is formed.
- Why it looks right
- The theory sounds convincing and the user wants a fast fix.
- Why it's wrong
- The methodology requires testing the theory to confirm the cause before planning and implementing a fix; untested replacements waste time and money.
Clue to watch for The question says the technician has just established a theory and asks what to do NEXT.
-
Repair a dying drive in place
- What candidates pick
- Run chkdsk with surface scan on a drive that is clicking and reporting S.M.A.R.T. errors.
- Why it looks right
- Disk utilities are the standard fix for disk errors.
- Why it's wrong
- Physical failure is in progress; heavy activity may destroy remaining data. Back up first, then replace.
Clue to watch for Clicking, grinding or a S.M.A.R.T. failure message.
-
Skipping the obvious display check
- What candidates pick
- Replace the projector bulb when the projector shows no signal from a newly connected laptop.
- Why it looks right
- Projector bulbs do burn out.
- Why it's wrong
- A no-signal message proves the lamp works; check the input source, cable and laptop display output mode first.
Clue to watch for The projector displays a message or menu but not the laptop image.
-
Bandwidth for call quality
- What candidates pick
- Upgrade the internet plan when VoIP calls are choppy but downloads are fast.
- Why it looks right
- More bandwidth sounds like it fixes everything.
- Why it's wrong
- Choppy calls with fast downloads indicate jitter or latency; QoS, wired connections or reducing congestion address it.
Clue to watch for Downloads are fine but real-time voice or video breaks up.
-
Using a swollen device
- What candidates pick
- Calibrate or fully discharge the battery of a phone with a bulging back.
- Why it looks right
- Calibration addresses many battery complaints.
- Why it's wrong
- Swelling indicates a damaged lithium-ion cell and a fire risk; stop use and replace it safely.
Clue to watch for A lifted touchpad, a separating case or a bulge.
-
Closing without verification
- What candidates pick
- Document and close the ticket immediately after replacing the failed part.
- Why it looks right
- The fix has been applied.
- Why it's wrong
- The method requires verifying full system functionality and implementing preventive measures before documenting the outcome.
Clue to watch for The question asks what to do after implementing the solution.
-
Wrong driver blamed on hardware
- What candidates pick
- Replace the printer's formatter board when pages print random symbols.
- Why it looks right
- Garbled output looks like hardware corruption.
- Why it's wrong
- Garbled print most often comes from an incorrect or corrupted driver; install the correct one first.
Clue to watch for Output is random characters rather than smears, lines or faded text.
Answer framework
Apply CompTIA's troubleshooting method to every Core 1 symptom question.
- Identify the problem by gathering details from the user, noting recent changes, and backing up data before making changes.
- Form a theory starting with the obvious, such as power, cables, input source and settings, and research the exact symptom wording if needed.
- Test the theory; if it is not confirmed, form a new one or escalate rather than replacing parts on a guess.
- Plan and implement the fix with safety first, powering down for burning smells or swollen batteries and protecting data on failing drives.
- Verify full functionality, add preventive measures such as cleaning, cooling or cable replacement, and document findings, actions and outcomes.
Practice question
Want more like this? The CompTIA A+ practice test has questions for every domain.
Checklist
0 of 12
Tick each one you can do without notes. Your ticks stay in this browser.
Study strategy
Begin with the troubleshooting methodology itself. Write the steps from memory until you can recite them, then practice identifying which step each action belongs to; many questions turn on that alone. Next, study 5.1 and 5.2 together, because power, heat, memory and drive faults share many symptoms. For each symptom in the objectives, write the most likely cause and the safest first action.
Then cover 5.5, using the networking domain as your reference: APIPA, interference, jitter and port flapping are the high-value items. Candidates commonly underestimate 5.6 printer troubleshooting, so build a defect table mapping each symptom to fuser, drum, toner, driver, spooler or paper path. Finish with 5.3 and 5.4, which reward a question-the-obvious approach and safety awareness for batteries and liquid damage.
Afterwards, practice mixed scenario sets under time pressure and include performance-based simulations if you can. For every miss, identify whether you misread the symptom, chose a fix out of order, or skipped a safety step. Then move to Core 2 domain 3.0, which applies the same reasoning to operating system and security problems.
FAQ
How much of Core 1 is troubleshooting?
Hardware and Network Troubleshooting is 28% of Core 1 (220-1201), the largest Core 1 domain.
Is the troubleshooting methodology still tested in V15?
Yes. The Core 1 objectives present the methodology alongside this domain rather than as a numbered objective, and its order drives many FIRST and NEXT questions across both exams.
What should I do first with a failing hard drive?
Back up the data while the drive still works. Repair utilities and reinstallation come later, if at all, because extra activity can finish off a failing drive.
How do I tell a fuser problem from a drum problem?
If toner smears or rubs off, the fuser is not bonding it. If a mark repeats at regular intervals or lines run down every page, look at the drum or imaging unit.
What causes poor VoIP quality when internet speed tests look fine?
Usually jitter or latency rather than bandwidth. Wired connections, QoS prioritization and reducing congestion or interference are the typical fixes.
What kind of questions appear in this domain?
Symptom-to-cause scenarios, FIRST and NEXT sequencing questions based on the methodology, and performance-based simulations of a faulty system or network.
How does this domain relate to the rest of A+?
It applies Core 1 domains 1.0 to 3.0 to failures, and the same method is used in Core 2 domain 3.0 for operating system, mobile app and security issues.
Other IT Fundamentals & Hardware certifications
Where the same subject shows up in other exams. Cards marked "Same subject" open the matching domain.
Test your Domain 5 knowledge
You have covered the troubleshooting methodology and the symptoms of power, drive, display, mobile, network and printer faults. Check whether you can choose the right first step in timed scenarios.
Keep going
- Training Training Built on your Weak areas
- Practice test Questions by domain, with explanations
- Mock exam Full length, timed like the real exam
- Readiness test Find your weakest domain in minutes
- Cheat sheet Key terms and formulas on one page
- Ask the CompTIA A+ AI tutor Get any concept explained your way