Quick Answer
The answer is loose GPU power cables. When the VGA LED is lit on the motherboard after GPU installation, it signals that the system’s firmware cannot detect the graphics card, which is almost always due to an incomplete physical or electrical connection. High-end GPUs require dedicated 6- or 8-pin power cables from the PSU; if even one of these is loose or unplugged, the card won’t initialize, leaving the screen blank despite fans spinning. On the CompTIA A+ Core 1 220-1201 exam, this scenario tests your ability to differentiate between power delivery issues and other POST failures—a common trap is assuming the GPU is defective or that the RAM caused the problem. Remember the mnemonic “VGA LED = Power First”: always check the GPU’s auxiliary power connectors before reseating the card, as this is the most frequent oversight during a new build or upgrade.
This 220-1201 practice question tests your understanding of core pc hardware troubleshooting. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A technician is configuring a new workstation for video editing. After installing a high-end GPU and additional RAM, the system powers on but the screen is blank. The motherboard has diagnostic LEDs; the VGA LED is lit. What is the most likely issue?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Incompatible RAM
Why wrong: RAM issues would light the DRAM LED, not the VGA LED.
Loose GPU power cables
High-end GPUs require dedicated power; if these are missing, the GPU will not initialize.
Faulty CPU
Why wrong: A faulty CPU would light the CPU LED, not the VGA LED.
Monitor set to wrong input
Why wrong: The VGA LED is a hardware diagnostic; it indicates the GPU itself is not detected, regardless of monitor settings.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Loose GPU power cables
A lit VGA diagnostic LED indicates the motherboard is not detecting the GPU. This is common when the GPU is not fully seated in the PCIe slot or when additional power cables are not connected. The technician should reseat the GPU and ensure all power connectors are attached.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Incompatible RAM
Why it's wrong here
RAM issues would light the DRAM LED, not the VGA LED.
Loose GPU power cables
Why this is correct
High-end GPUs require dedicated power; if these are missing, the GPU will not initialize.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
Faulty CPU
Why it's wrong here
A faulty CPU would light the CPU LED, not the VGA LED.
Monitor set to wrong input
Why it's wrong here
The VGA LED is a hardware diagnostic; it indicates the GPU itself is not detected, regardless of monitor settings.
Common exam traps
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 220-1201 NAT questions on configuration and troubleshooting.
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FAQ
Core PC Hardware Troubleshooting — This question tests Core PC Hardware Troubleshooting — Static NAT maps one inside address to one outside address..
The correct answer is: Loose GPU power cables — A lit VGA diagnostic LED indicates the motherboard is not detecting the GPU. This is common when the GPU is not fully seated in the PCIe slot or when additional power cables are not connected. The technician should reseat the GPU and ensure all power connectors are attached.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 220-1201 NAT questions on configuration and troubleshooting.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Static NAT maps one inside address to one outside address.
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Last reviewed: Jun 18, 2026
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