Computer Powers On for 2 Seconds Then Shuts Down: Why the Motherboard Is Likely the Culprit
A desktop computer powers on for about two seconds (fans spin, LEDs flash) then immediately shuts down. It repeats this cycle if the power button is pressed again. The technician has already replaced the power supply with a known-good unit, removed and reseated all expansion cards and memory modules, and tested the system outside the case on a non-conductive surface. The problem persists. Which of the following is the MOST likely cause?
Quick Answer
The answer is a faulty motherboard. This is the correct choice because the symptom of a computer powering on for two seconds then shutting down in a repeating cycle is the classic signature of a short circuit or critical failure in the motherboard’s power regulation (VRM) or CPU initialization path. Since the technician has already replaced the power supply with a known-good unit, reseated all memory and expansion cards, and tested the system outside the case—which eliminates case shorts—the only remaining component that can trigger this immediate overcurrent or thermal protection is the motherboard itself. On the CompTIA A+ Core 1 220-1101 exam, this scenario tests your ability to isolate motherboard faults after ruling out the PSU, RAM, and case grounding. A common trap is to suspect the CPU or RAM again, but the repeating two-second cycle points directly to a motherboard-level failure, not a component seating issue. Memory tip: think “two-second loop, motherboard’s the scoop”—if the PSU and reseating don’t fix it, the board is the culprit.
⚠ Common exam trap
CompTIA often tests the misconception that a faulty CPU or RAM will cause an immediate power cycle, but in reality, a CPU or RAM failure typically results in a system that stays powered on with no display or beeps, not a precise 2-second shutdown loop.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The motherboard is faulty
The symptom of powering on for about two seconds and then immediately shutting down, followed by a repeating cycle, is classic for a short circuit or a critical motherboard failure. Since the technician has already replaced the power supply with a known-good unit, reseated all components, and tested the system outside the case (eliminating case shorts), the only remaining component that can cause this exact behavior is the motherboard itself. A faulty motherboard can fail to initialize the CPU or power regulation (VRM) correctly, triggering the system's overcurrent or thermal protection within seconds.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The motherboard is faulty
Why this is correct
With power supply, expansion cards, memory and case grounding eliminated, the boot loop points to the motherboard failing POST initialisation. Capacitors or voltage regulators on the board cannot sustain power delivery, causing the immediate shutdown after two seconds, which matches the persistent symptom.
- ✗
The CPU is faulty
Why it's wrong here
A faulty CPU generally produces no POST, beep codes or a blank display rather than a repeatable two-second power cycle, and the described reseating did not include the CPU. CPU replacement is warranted after confirming socket damage or bent pins, not from this symptom pattern.
- ✗
The RAM is incompatible
Why it's wrong here
Incompatible RAM usually prevents POST with beep codes or a blank screen rather than causing a two-second shutdown loop, and reseating memory was already performed. Compatibility matters when matching module speed, rank or voltage to the motherboard's qualified vendor list, not for this symptom.
- ✗
The graphics card is drawing too much power
Why it's wrong here
A graphics card exceeding the PSU's 12 V rail budget typically causes shutdowns under gaming or rendering load, not within two seconds of pressing power. Adequate wattage and PCIe power connector selection is the relevant scenario, and a known-good PSU was already fitted.
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Same concept, more angles
2 more ways this is tested on 220-1101
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A technician is troubleshooting a desktop computer that powers on for about one second and then shuts down. The technician has already removed all expansion cards and disconnected all drives. The system still exhibits the same behavior with only the CPU, motherboard, one RAM stick, and power supply connected. Which of the following is the MOST likely cause?
hard- A.A faulty CMOS battery.
- ✓ B.An incorrectly installed motherboard standoff causing a short circuit.
- C.Incompatible RAM speed.
- D.Overheating CPU due to improper thermal paste application.
Why B: The symptom of powering on for about one second and then shutting down, even with only the CPU, motherboard, one RAM stick, and power supply connected, strongly indicates a short circuit. An incorrectly installed motherboard standoff that contacts the motherboard's traces or solder points can create a direct short to ground, triggering the power supply's overcurrent protection (OCP) and causing an immediate shutdown. This behavior persists regardless of other components because the short is on the motherboard itself.
Variation 2. A technician is troubleshooting a desktop computer that powers on for about two seconds and then immediately shuts down. The case fans spin briefly, the CPU fan starts, then everything stops. The technician has tested the power supply with a multimeter and all voltages are within specification. The technician has also removed all add-on cards, disconnected all drives, and reseated the RAM and CPU power cables. The problem persists. Which of the following is the MOST likely cause?
hard- A.Faulty power button
- ✓ B.Short circuit in the case or motherboard
- C.Failing CPU
- D.Incompatible RAM
Why B: The symptom of powering on for about two seconds and then immediately shutting down is classic for a short circuit protection mechanism. When the power supply detects a short (e.g., from a standoff in the wrong hole, a loose screw, or a damaged motherboard trace), it triggers overcurrent protection (OCP) or short-circuit protection (SCP) and cuts power to prevent damage. Since the technician verified the power supply voltages are good and reseated all connections, the most likely remaining cause is a short circuit in the case or motherboard.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 220-1101 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 220-1101 exam.