When starting the engine of a truck with a trailer, you can tell that your vehicle's ABS is not working if:
Detailed Explanation
The correct answer is "The yellow light on the left rear of the trailer stays on". This question tests general CDL knowledge and the safest action expected of a commercial driver. Because the prompt uses negative wording, identify the normally correct safety rules first, then select the exception.
Correct Answer: The yellow light on the left rear of the trailer stays on
Why This Matters on the CDL Test
Use this as part of your General Knowledge review. The real CDL knowledge test rewards drivers who understand the reason behind each rule, not only the answer letter, so read the explanation and then try a few related questions.
How to Remember It
Say the rule in your own words, then explain why the wrong answers are unsafe or incomplete. That habit makes similar General Knowledge questions easier when the exam changes the wording.
Answer Review
Choose "The yellow light on the left rear of the trailer stays on" because this answer matches the safe CDL action for general knowledge knowledge. On the knowledge test, the safest answer is usually the one that protects space, control, visibility, legal compliance, or inspection accuracy before the vehicle is put at risk.
Why the other answers are weaker
- The engine makes a strange noise"The engine makes a strange noise" does not best answer this general knowledge knowledge question. When you see a similar option on the CDL permit test, compare it against the exact safety rule and choose the answer that prevents the most immediate risk.
- The trailer detaches"The trailer detaches" does not best answer this general knowledge knowledge question. When you see a similar option on the CDL permit test, compare it against the exact safety rule and choose the answer that prevents the most immediate risk.
Test-Day Checklist
- Read the question once for the topic, then read it again for the exact CDL action being tested in General Knowledge.
- Eliminate answers that sound convenient but skip an inspection, warning sign, or safety step.
- Say the correct rule out loud before moving on so you can recognize it when the exam changes the wording.
Ready to practice for real?
Take our free, full-length General Knowledge practice test. Simulates the actual DMV exam with timed questions.
Start Practice TestRelated Questions
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When starting an engine, oil pressure should come up to a normal level:
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118. Which of these will help keep an engine cool in hot weather?
149. Your truck has a dual air system and one of the systems loses its pressure. What will happen?
Keep Studying General Knowledge
Question pages help you review one rule at a time. To build test-day speed, move back into the full General Knowledge practice test and answer a mixed set without looking at the explanation first.
State CDL Practice Paths
After you understand this answer, use a state practice path to connect the federal CDL rule with the DMV test pages drivers search for most.