CPU Power Connector Missing — No Display and CPU LED Diagnosis
A technician is building a new desktop computer. After installing the CPU, RAM, and power supply, the system powers on and fans spin, but the monitor displays 'No Signal'. The technician has verified the monitor and cable work with another computer. Which of the following should the technician check FIRST?
⚠ Common exam trap
CompTIA often tests the misconception that a system powering on with spinning fans means all power connections are correct, when in fact the CPU power connector is a separate, easily overlooked connection that can cause a no-POST condition.
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
✓
Ensure the CPU power connector is plugged in
The CPU power connector (typically a 4+4 pin 12V EPS connector) provides dedicated power to the CPU. Without it, the CPU cannot initialize, so the system may power on and spin fans but fail to POST, resulting in a 'No Signal' display. Since the monitor and cable are verified working, the most logical first check is this power connection.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Ensure the CPU power connector is plugged in
Why this is correct
The CPU power connector (typically the 4-pin or 8-pin EPS12V leads) supplies dedicated 12V power to the processor's voltage regulator module (VRM), which generates the core voltage (Vcore) needed for the CPU to operate. Without this connection, the CPU cannot initialize, yet the motherboard's main 24-pin power can still spin case fans and power other peripherals, producing a classic no-display condition with spinning fans. This is the most fundamental check because the CPU is the first major component to initialize during POST, and without Vcore no further boot activity occurs.
- ✗
Replace the RAM with known good modules
Why it's wrong here
Insufficient or faulty RAM usually causes a specific POST failure signature: the system emits a series of beep codes (e.g., continuous or repeating pattern depending on BIOS vendor) or enters a power-on/power-off boot loop as the motherboard attempts memory training and fails. It does not typically produce a steady, silent state with all fans spinning but no display, which is a hallmark of the CPU not receiving power. Replacing RAM before verifying CPU power is therefore an unnecessary step that wastes time; the symptom pattern points to a lack of CPU initialization, not memory training failure.
When this WOULD be correct
If the system powers on but beeps repeatedly or fails to POST, and the RAM is suspected faulty (e.g., after a power surge), replacing with known good modules would be the correct first step.
- ✗
Reseat the GPU in its slot
Why it's wrong here
Reseating the GPU addresses loose installation or poor contact between the PCIe slot and the graphics card, which could cause a lack of video output if the GPU is the primary display adapter. However, this action assumes the CPU, RAM, and power delivery are already functional enough for the system to enumerate the PCIe bus and initialize the GPU. If the CPU power connector is unplugged, the processor cannot execute instructions to configure the PCIe bus, so the GPU will not be detected or initialized regardless of how well it is seated; therefore, checking CPU power is the more fundamental first step in the troubleshooting sequence.
When this WOULD be correct
If the technician had already verified the CPU power connector is connected and the system still shows 'No Signal', then reseating the GPU would be a logical next step to check for a loose connection.
- ✗
Check the BIOS settings for video output
Why it's wrong here
BIOS settings cannot be accessed or modified without successful POST, and POST cannot occur when the CPU has no power. A total absence of video output, with fans spinning but no beep or splash screen, indicates the system is failing before the firmware even starts executing, so there is no opportunity to display or change video output settings. Even if the CMOS settings were misconfigured for a video output, the system would typically still attempt to initialize the video device during POST and produce some signal, but without CPU power it never reaches that stage.
When this WOULD be correct
If the system had video output initially but later lost it after a BIOS update or configuration change, checking BIOS settings for video output (e.g., primary display adapter) would be the correct first step.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 220-1101 exam frequently reuses these exact scenarios with slightly different constraints.
✓Ensure the CPU power connector is plugged inCorrect answer▾
Why this is correct
The CPU power connector (typically the 4-pin or 8-pin EPS12V leads) supplies dedicated 12V power to the processor's voltage regulator module (VRM), which generates the core voltage (Vcore) needed for the CPU to operate. Without this connection, the CPU cannot initialize, yet the motherboard's main 24-pin power can still spin case fans and power other peripherals, producing a classic no-display condition with spinning fans. This is the most fundamental check because the CPU is the first major component to initialize during POST, and without Vcore no further boot activity occurs.
✗Replace the RAM with known good modulesWrong answer — click to see why▾
Why this is wrong here
The system powers on and fans spin, indicating the RAM is likely functional. The 'No Signal' issue with a known-good monitor/cable points to a power or connection problem with the CPU or GPU, not RAM.
★ When this WOULD be the correct answer
If the system powers on but beeps repeatedly or fails to POST, and the RAM is suspected faulty (e.g., after a power surge), replacing with known good modules would be the correct first step.
Why candidates choose this
Candidates often default to RAM as a common cause of boot failures, especially when other components seem to work, overlooking that the CPU power connector is a more likely culprit here.
✗Reseat the GPU in its slotWrong answer — click to see why▾
Why this is wrong here
The system powers on and fans spin, indicating the GPU is likely seated. The issue is more fundamental: the CPU power connector is missing, which prevents the CPU from initializing, causing no video output.
★ When this WOULD be the correct answer
If the technician had already verified the CPU power connector is connected and the system still shows 'No Signal', then reseating the GPU would be a logical next step to check for a loose connection.
Why candidates choose this
Candidates often assume that a 'No Signal' error is always due to the GPU, especially when fans spin, leading them to reseat the GPU without considering the CPU power requirement.
✗Check the BIOS settings for video outputWrong answer — click to see why▾
Why this is wrong here
The monitor displays 'No Signal' and the system powers on, but the BIOS settings cannot be accessed without video output. Checking BIOS settings requires a working display, which is not present, so this step is premature.
★ When this WOULD be the correct answer
If the system had video output initially but later lost it after a BIOS update or configuration change, checking BIOS settings for video output (e.g., primary display adapter) would be the correct first step.
Why candidates choose this
Candidates may think the issue is a misconfigured video output in BIOS, but they overlook that BIOS access requires a working display, making this check impossible without first resolving the no-signal issue.
Analysis generated from the official 220-1101blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Go deeper
Related to this question
Learn chapter
PSU Connector Types: 24-pin, PCIe, SATA
Key term
Power-on Self-test
The Power-on Self-test (POST) is a diagnostic process a computer runs immediately when you turn it on to check that essential hardware components are working correctly before loading the operating system.
Key term
Dual In-line Memory Module
A Dual In-line Memory Module (DIMM) is a small circuit board that holds memory chips and plugs into a computer's motherboard to provide Random Access Memory (RAM).
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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.