CompTIA A+: Hardware and Network Troubleshooting Concepts
Importance ★★★★★ · 28% (estimate)
Overview
This is the largest part of Core 1. It asks you to use CompTIA's troubleshooting steps on real problems with PCs, laptops, phones, storage, printers, and networks. Most questions describe what a user sees and ask for the most likely cause or the best next step.
The troubleshooting steps are: identify the problem, establish a theory of probable cause, test the theory, establish a plan of action and put the fix in place, verify full system functionality and add preventive measures, and document what you found and did. While identifying the problem, ask the user questions, check for recent changes, and back up data before you change anything. If a theory turns out wrong, form a new one or escalate.
Some symptoms point clearly to a cause. A PC that shuts off after running for a while may be overheating. A clock that resets after power is removed points to the CMOS battery. Grinding or clicking from a hard drive warns of failure, so back up at once. On networks, a 169.254 address points to a DHCP problem, and being able to reach an IP address but not a name points to DNS.
Key concepts
Identify the problem
The first step: gather information from the user, find out what changed, duplicate the problem if you can, and back up data before making changes.
Memory tipAsk what changed first.
Theory of probable cause
Your best guess about the cause. Start with the simple, obvious causes first, such as power and cables.
Memory tipQuestion the obvious.
Verify and document
After the fix, confirm the whole system works and add preventive steps, then record the problem, the actions taken, and the result.
Memory tipLast step = document.
CMOS battery
A small coin battery on the motherboard that keeps the firmware clock and settings when the PC is unplugged.
Memory tipWrong date after every power-off = replace the CMOS battery.
Overheating
Dust, failed fans, or dried thermal paste can make a PC shut off or slow down under load.
Memory tipShuts off after a while = check fans and dust.
Loopback plug
A connector that sends a port's output straight back into its input to test whether the network port works.
Memory tipTest the NIC port itself = loopback plug.
Often tested
- If a theory is not confirmed, form a new theory or escalate.
- Faded laser prints usually mean low toner; smeared toner points to the fuser.
- Limited or no connectivity with a 169.254 address: check the DHCP server and the cable or Wi-Fi link.
- A degraded RAID 5 still works after one failed drive; replace the failed drive soon so the array can rebuild.
- No display but the PC powers on: check the monitor input, cable, and that the cable is in the graphics card port.
3 sample questions
Verified practice questions from this unit.
Question 1. According to the CompTIA troubleshooting steps, what should a technician do first?
- ① Identify the problem
- ② Test the theory to determine the cause
- ③ Document findings, actions, and outcomes
- ④ Establish a theory of probable cause
▼ Show answer and explanation▲ Hide answer and explanation
Answer: ① Identify the problem
Key point: Step 1 = identify the problem
The CompTIA troubleshooting steps start with identifying the problem: talk to the user, find out what changed, try to repeat the problem, and back up data before making changes. Only then does the technician form and test a theory.
Wrong choices
- Test the theory to determine the cause: Testing comes after a theory has been formed.
- Document findings, actions, and outcomes: Documenting is the last step, after the problem is fixed and verified.
- Establish a theory of probable cause: A theory comes second, after the technician has gathered information about the problem.
Question 2. Every morning, a PC that is unplugged overnight shows the wrong date and time, and the firmware settings are back to defaults. What is the most likely cause?
- ① The hard drive is failing
- ② The CMOS battery is dead
- ③ The power supply is failing
- ④ The time zone is set wrong in Windows
▼ Show answer and explanation▲ Hide answer and explanation
Answer: ② The CMOS battery is dead
Key point: Clock and settings reset = replace CMOS battery
A small coin battery on the motherboard keeps the firmware clock and settings when the PC has no power. When that battery dies, the clock and settings reset every time the PC is unplugged. Replacing the battery fixes it.
Wrong choices
- The hard drive is failing: A failing drive causes slow access, errors, or noises. It does not reset the clock or firmware settings.
- The power supply is failing: A failing power supply causes shutdowns or no power, not lost settings after the PC is unplugged.
- The time zone is set wrong in Windows: A wrong time zone gives a time that is off by a set amount every day. It does not reset the firmware settings.
Question 3. A desktop PC shuts off by itself after about 20 minutes of gaming. After it sits for a while, it starts normally again. What should the technician check first?
- ① The CMOS battery
- ② The network cable
- ③ The fans and heatsinks for dust or failure
- ④ The amount of free disk space
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Answer: ③ The fans and heatsinks for dust or failure
Key point: Shuts off under load, fine after cooling = overheating
A PC that turns off after working hard for a while, then starts fine once it cools, is most likely overheating. Dust-clogged heatsinks, failed fans, or dried-out thermal paste are common causes. The PC shuts itself off to protect the parts.
Wrong choices
- The CMOS battery: A dead CMOS battery resets the clock and settings. It does not cause shutdowns under load.
- The network cable: A loose network cable drops the internet connection but does not shut the PC off.
- The amount of free disk space: Low disk space slows the PC down but does not make it turn off.
AI-written · Verified · Written by AI. Only units that passed a separate AI check (re-reading facts and numbers) are published. Tell us if you find a mistake.