Computer Powers On Then Shuts Down: CPU Power Connector Seating
A technician is replacing a failed power supply in a desktop computer. After installing the new power supply unit (PSU), the computer powers on for a few seconds and then shuts down completely. The technician has verified all cable connections are secure. The motherboard requires an 8-pin CPU power connector and a 24-pin main connector. The new PSU provides a 4+4 pin CPU cable and a 20+4 pin main cable. The technician connected the 4+4 pin cable by combining the two halves and inserting them into the motherboard's 8-pin CPU power socket. Which of the following should the technician check NEXT?
Quick Answer
The correct next step is to verify the 4+4 pin CPU cable is fully seated and the latch clicks. This is because the 4+4 pin connector must be inserted completely into the motherboard’s 8-pin CPU power socket to ensure solid electrical contact; if it is even slightly loose, the system can power on briefly from the initial surge of power but then shut down when the CPU draws higher current, triggering overcurrent protection or a voltage drop. On the CompTIA A+ Core 1 220-1101 exam, this scenario tests your understanding of power supply installation and the common symptom of a computer that powers on then shuts down after PSU replacement—a classic trap is assuming all connections are secure without physically checking the latch. A helpful memory tip: if the system starts and stops like a hiccup, check the CPU power plug’s click.
⚠ Common exam trap
Watch out — candidates often assume a brief power-on followed by shutdown indicates a faulty PSU or insufficient wattage, rather than checking the most basic physical connection issue with the CPU power connector.
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
✓
Verify the 4+4 pin CPU cable is fully seated and the latch clicks
The 4+4 pin CPU cable must be fully seated and latched to ensure proper electrical contact. If the connector is not fully inserted, the system may start briefly due to initial power but then shut down when the CPU draws more current, triggering overcurrent protection or a voltage drop. The fact that the system powers on for a few seconds and then shuts down is a classic symptom of a loose or improperly seated CPU power connector.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Replace the PSU with a higher wattage unit
Why it's wrong here
Wattage is irrelevant when the PSU already powers the board briefly; the fault lies in the 4+4 CPU cable orientation or seating, since reversed halves short the 12V rail. A higher-wattage unit is tempting when shutdowns suggest overload, and would be correct if total component draw genuinely exceeded the existing PSU's rating.
- ✓
Verify the 4+4 pin CPU cable is fully seated and the latch clicks
Why this is correct
Intermittent shutdown after POST typically means the CPU power connector is not fully engaged; the 4+4 halves can appear inserted without latching, so reseating until the latch clicks confirms the 8-pin socket receives stable power.
- ✗
Check if the CPU fan is connected to the correct header
Why it's wrong here
A missing CPU fan signal triggers an immediate protective shutdown, but the board here powers on for several seconds, indicating power delivery rather than thermal protection. Checking the header is tempting because fan-tach faults cause similar symptoms, and would be correct if the system halted instantly with no POST activity.
- ✗
Reset the BIOS by removing the CMOS battery
Why it's wrong here
Clearing CMOS resets BIOS settings such as boot order and clock, but cannot remedy a miswired CPU power connector, and the board already POSTs. It is tempting as a generic first step after hardware changes, and would be correct when firmware settings, not cabling, prevent a stable start.
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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 rebuilding a desktop PC after a motherboard failure. The technician installs a new motherboard that supports DDR4-3200, an Intel Core i5-11400 CPU, and 2x8GB of DDR4-3200 RAM. The system powers on for about 10 seconds, then shuts down and immediately restarts, repeating this cycle indefinitely. The technician has verified that the CPU cooler is properly mounted with thermal paste and that the RAM is fully seated in the correct slots (A2 and B2). Which of the following is the MOST likely cause of the issue?
hard- ✓ A.CPU power connector is not fully seated
- B.RAM modules are not installed in the correct slots
- C.The motherboard BIOS does not support the Intel Core i5-11400 CPU
- D.Power supply wattage is insufficient for the new components
Why A: The most likely cause is that the CPU power connector (typically the 4+4 pin 12V EPS connector) is not fully seated. Without proper power delivery to the CPU, the system will attempt to start, fail the Power-On Self-Test (POST) due to a CPU initialization error, and then automatically reboot in a continuous loop. The technician has already verified RAM seating and cooler installation, making an incomplete CPU power connection the primary suspect.
Variation 2. A technician is upgrading a desktop computer with a new CPU and motherboard. After installation, the computer powers on but the monitor displays 'No Signal'. The technician verifies the monitor works, and the GPU fans spin. The motherboard has no onboard video. Which of the following should the technician do FIRST?
medium- A.Reseat the GPU
- ✓ B.Check the CPU power connector
- C.Clear the CMOS
- D.Update the BIOS
Why B: The CPU power connector (typically a 4+4 pin EPS12V connector) supplies dedicated power to the CPU. If it is not connected or is loose, the CPU will not initialize, causing the system to power on (fans spin, lights come on) but fail to POST, resulting in a 'No Signal' display. Since the GPU fans spin and the monitor works, the issue is likely a lack of CPU power, making checking this connector the first logical step.
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.