CDT Vehicle Operations & Maintenance 2 — Questions and Answers
Question 1: When should a commercial driver perform a post-trip inspection?
- Only when the vehicle shows warning lights
- At the end of every driving shift before releasing the vehicle (Correct answer)
- Once per week regardless of usage
- Only after long-distance hauls exceeding 500 miles
Correct answer: At the end of every driving shift before releasing the vehicle
Federal regulations require a post-trip inspection report at the end of each driving shift to document any defects found.
Question 2: What is the primary purpose of the vehicle's differential?
- To increase engine horsepower
- To allow drive wheels to rotate at different speeds during turns (Correct answer)
- To engage the parking brake automatically
- To regulate air pressure in the brake system
Correct answer: To allow drive wheels to rotate at different speeds during turns
The differential allows the outer and inner drive wheels to rotate at different speeds when the vehicle turns, preventing tire scrub.
Question 3: What does a red triangle warning light on the dashboard typically indicate?
- Low fuel level
- A hazard warning system activation or critical fault (Correct answer)
- Cruise control is engaged
- Trailer air supply is connected
Correct answer: A hazard warning system activation or critical fault
A red triangle or warning indicator typically signals a critical system fault requiring immediate attention before continuing operation.
Question 4: Which of the following best describes 'jake braking' (engine brake)?
- Using the parking brake to slow the vehicle gradually
- Compressing air in cylinders to create engine retardation (Correct answer)
- Downshifting without using the clutch
- Applying brakes intermittently to prevent lockup
Correct answer: Compressing air in cylinders to create engine retardation
Jake braking uses the engine's compression to retard vehicle speed, reducing wear on service brakes especially on downgrades.
Question 5: A driver notices the steering wheel vibrates at highway speeds but not at lower speeds. The MOST likely cause is:
- Low power steering fluid
- Wheel imbalance or tire defect (Correct answer)
- Incorrect tire pressure on the trailer
- Worn windshield wiper blades
Correct answer: Wheel imbalance or tire defect
Steering wheel vibration at highway speeds is classically caused by wheel imbalance or a defective tire creating oscillation at higher RPMs.
Question 6: What is the correct action when the low air pressure warning activates in an air brake system?
- Continue driving and monitor the gauge
- Immediately bring the vehicle to a safe stop (Correct answer)
- Switch to manual brake mode
- Increase engine RPM to rebuild pressure
Correct answer: Immediately bring the vehicle to a safe stop
When the low air pressure warning activates (typically below 60 psi), drivers must stop safely immediately because spring brakes will automatically apply at about 20-45 psi.
Question 7: Which maintenance item should be checked MOST frequently on a commercial vehicle operating in hot weather?
- Windshield washer fluid level
- Coolant level and cooling system function (Correct answer)
- Cabin air filter condition
- Spare tire pressure
Correct answer: Coolant level and cooling system function
High ambient temperatures increase engine heat load, making coolant level and cooling system efficiency the most critical check to prevent overheating.
CDT Vehicle Operations & Maintenance 2
When should a commercial driver perform a post-trip inspection?