To inspect the engine compartment, when might it be necessary for you to tilt the cab?

If you want to inspect the driveshaft

If you suspect a problem in the drivetrain

If the vehicle was in an accident

Which of the following do you NOT have to do during the in-cab inspection?

Check that the steps leading to the cab entry are solid, clear of objects, and securely bolted to the frame.

Put the gear shift in neutral (for a manual) or park (for an automatic).

Make sure the parking brake is on.

Start the engine and listen for unusual noises.

What is the sliding mechanism and locking device for tandem axles on trailers?

Tandem release arm / locking pins

The Class B and Class C vehicle inspection tests include an inspection of

the special features of the vehicle.

You are checking your steering and exhaust systems during a pre-trip inspection. Which of these statements is true?

Excessive steering wheel play can make it hard to steer.

Leaks in the exhaust system are not a problem if they are outside of the cab.

Some leakage of power steering fluid is normal.

If the examiner asks you to check the coolant level, you should NOT

remove the radiator cap if the engine might be hot.

remove the radiator cap if the engine is cool to the touch.

check the sight glass or the coolant reservoir.

tell the examiner how you would do it.

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20 questions
Pass mark 80%

Idaho CDL: Pre-Trip Inspection Practice Test

20 pre-trip inspection questions for the Idaho CDL Knowledge Test, out of 91 in the app. Answer each to see whether you got it right and why. The real Idaho Pre-Trip Inspection test has 20 questions and you need 16 correct (80%) to pass.

Facts updated Oct 26, 2026
Official source: law.cornell.edu
Independent, not affiliated with the DMV. How we write our questions

How it works

1Pick an answer20 questions, one tap each.
2See the ruleRight or wrong, every answer is explained.
3Get your scoreCompared with the real 80% pass mark.

Start the test

0/20 answered0 correctPass mark 80%

1Question 1 of 20
Which gauge indicates the alternator or generator is charging?
Not quite. The answer is Ammeter or voltmeter
During your pre-trip inspection, check the ammeter gauge or voltmeter gauge to make sure that the alternator or generator is charging properly or the warning light is off.
2Question 2 of 20
What heats the cab and prevents frost from forming on the windshield?
Not quite. The answer is Heater/defroster
The heater/defroster provides a stream of warmed air. By selecting the appropriate vents, you can choose whether the air will heat the cab or melt frost on the windshield.
3Question 3 of 20
Which tires should have a minimum tread depth of 4/32 inch?
Not quite. The answer is Steering axle tires
The tires on the steering axle should have at least 4/32 inch of tread, and all other tires should have at least 2/32 inch of tread. Inadequate tread on the front tires increases the risk of a front-wheel skid.
4Question 4 of 20
When you inspect the air lines, which sense should you use to check for air leaks?
Not quite. The answer is Hearing
When you inspect the air lines, listen for the telltale hiss of escaping air, which indicates an air leak.
5Question 5 of 20
To inspect the engine compartment, when might it be necessary for you to tilt the cab?
Not quite. The answer is If it's a cab-over vehicle
In a conventional vehicle, the engine is mounted forward of the driver. In a cab-over vehicle (also known as a cab-forward vehicle), the cab is located above, or even in front of, the front axle. To inspect a cab-over vehicle, it may be necessary for you to tilt the cab to gain access to the engine compartment. Before doing this, secure any loose items inside the cab so they won't fall when you tilt the cab.
6Question 6 of 20
Which of the following do you NOT have to do during the in-cab inspection?
Not quite. The answer is Check that the steps leading to the cab entry are solid, clear of objects, and securely bolted to the frame.
During the in-cab inspection, shift into neutral (for a manual) or park (for an automatic) and make sure the parking brake is on. Start the engine and listen for unusual noises. (You do inspect the steps to the cab during the pre-trip inspection, but not during the in-cab part of the inspection.)
7Question 7 of 20
Which gauge helps you prevent engine failure, seizure, or breakdown?
Not quite. The answer is Oil pressure
During your pre-trip inspection, make sure that the oil pressure gauge is working and it shows normal or increasing oil pressure. Running the engine without oil will eventually cause serious damage.
8Question 8 of 20
You are looking for puddles on the ground and dripping fluids on the underside of the engine and transmission. What are you checking for?
Not quite. The answer is Leaks
As part of your engine inspection, check the ground below the engine compartment for puddles or dripping liquids.
9Question 9 of 20
Which of the following is a way to check the coolant level?
Not quite. The answer is Check the sight glass.
Your vehicle may provide a way for you to check the coolant level even when the engine is hot. Such devices include reservoir sight glasses, see-through coolant overflow containers, and coolant recovery containers.
10Question 10 of 20
You are checking for damage to the longitudinal members, cross members, box, or floor. What are you inspecting?
Not quite. The answer is Frame
The frame consists of the structural members for supporting the body of the vehicle or trailer. When inspecting the frame, (1) check for cracks; (2) check for broken welds; and (3) check for illegal holes or other damage to the longitudinal frame members, cross members, box, or floor.
11Question 11 of 20
Which of these converts air pressure to mechanical force to operate the brake at a wheel?
Not quite. The answer is Brake chamber
The brake chamber (one at each wheel) converts air pressure to mechanical force to operate the brake at that wheel. When you press the brake pedal, compressed air from a service tank enters the brake chamber. Air pressure pushes out the brake chamber's pushrod, which moves the slack adjuster. The moving slack adjuster applies the brake.
12Question 12 of 20
What is the sliding mechanism and locking device for tandem axles on trailers?
Not quite. The answer is Tandem release arm / locking pins
If so equipped, make sure that the locking pins are locked in place and the release arm is secured.
13Question 13 of 20
The Class B and Class C vehicle inspection tests include an inspection of
Not quite. The answer is the special features of the vehicle.
Class B and Class C CDLs cover the operation of a wide variety of different types of vehicles with their own special features. You must perform the vehicle inspection test on a vehicle that is representative of the kinds of vehicles that you plan to drive professionally. As part of the test, you will have to inspect any special features of your vehicle (such as the special features of school buses if you're using one for the test).
14Question 14 of 20
If worn, what can cause excessive heat buildup from a reduced ability to absorb and dissipate heat, possibly leading to loss of brake response?
Not quite. The answer is Brake drum / linings
Brake linings use friction to turn the vehicle's kinetic energy into heat. However, excessive heat from overuse of the brakes may cause the brake linings to wear out faster, leading to brake fade or failure. Also, if one brake is out of adjustment and can't do its job, the other brakes will have to work harder, causing them to overheat.
15Question 15 of 20
Steering wheel play should NOT exceed ____ degrees.
Not quite. The answer is 10
If there is more than 10 degrees of play in your steering wheel, your vehicle will be harder to steer. Have the problem corrected before you drive the vehicle. Ten degrees is equivalent to about 1¾ inches at the rim of a 20-inch steering wheel. According to federal regulations, there must not be more than 2½ inches of play at the rim of a 20-inch steering wheel.
Source: 49 CFR 570.60
16Question 16 of 20
You are checking your steering and exhaust systems during a pre-trip inspection. Which of these statements is true?
Not quite. The answer is Excessive steering wheel play can make it hard to steer.
If there is more than 10 degrees of play in your steering wheel, it will be harder for you to tell which way your front wheels are pointed. Have the problem corrected before you drive the vehicle. Ten degrees is equivalent to about 1¾ inches at the rim of a 20-inch steering wheel. According to federal regulations, there must not be more than 2½ inches of play at the rim of a 20-inch steering wheel.
Source: 49 CFR 570.60
17Question 17 of 20
Which of these keeps your vehicle from rolling when it's parked?
Not quite. The answer is Parking brake
The parking brake keeps your vehicle from moving when it's parked. The mechanism is separate from the service brakes that you use in normal driving.
18Question 18 of 20
If the examiner asks you to check the coolant level, you should NOT
Not quite. The answer is remove the radiator cap if the engine might be hot.
If the engine is cool to the touch of your bare hand, you can probably remove the radiator cap and check the coolant level safely. If the engine is hot, do NOT remove the radiator cap; it's dangerous. If there is a sight glass or coolant reservoir, you can use it to check the coolant level. Otherwise, just tell the examiner how you would check the coolant level by removing the radiator cap once the engine is cool.
19Question 19 of 20
What should you check to be sure it is solid, clear of objects, and securely bolted to the tractor frame?
Not quite. The answer is Catwalk
Check that the steps leading up to the cab and catwalk (if any) are clear of obstructions and secured to the tractor frame.
20Question 20 of 20
Which of the following can disengage the engine from the drivetrain?
Not quite. The answer is Clutch and gearshift
To ensure that your vehicle doesn't move once you start the engine, first depress the clutch (unless the vehicle has an automatic transmission) and put the gearshift in neutral (or Park for an automatic transmission). Once the engine has started, slowly release the clutch.

Questions people ask

Is this Idaho CDL: Pre-Trip Inspection Practice Test like the real Idaho CDL Knowledge Test?

The questions are written in the same style as the real test, from official sources, with an explanation for each answer. The real test has 20 questions; this free test has 20.

How many questions are on the Idaho CDL Knowledge Test?

The General Knowledge test has 20 questions. Each class and endorsement adds its own test.

What score do you need to pass the Idaho CDL Knowledge Test?

You need 16 out of 20 correct (80%).

How old do you have to be to take the Idaho CDL Knowledge Test?

You can take it from age 18.

Where can I practice more questions?

The Driving Exam Prep app has the full question bank for your test, a step-by-step roadmap, a mistakes review and a readiness score against the real pass mark.

Official sources

Our questions are written from these official sources. Always study your official handbook too: rules change, and our practice questions may differ from your real test.

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Which gauge indicates the alternator or generator is charging?

What heats the cab and prevents frost from forming on the windshield?

Which tires should have a minimum tread depth of 4/32 inch?

When you inspect the air lines, which sense should you use to check for air leaks?

To inspect the engine compartment, when might it be necessary for you to tilt the cab?

Which of the following do you NOT have to do during the in-cab inspection?

Which gauge helps you prevent engine failure, seizure, or breakdown?

You are looking for puddles on the ground and dripping fluids on the underside of the engine and transmission. What are you checking for?

Which of the following is a way to check the coolant level?

You are checking for damage to the longitudinal members, cross members, box, or floor. What are you inspecting?

Which of these converts air pressure to mechanical force to operate the brake at a wheel?

What is the sliding mechanism and locking device for tandem axles on trailers?

The Class B and Class C vehicle inspection tests include an inspection of

If worn, what can cause excessive heat buildup from a reduced ability to absorb and dissipate heat, possibly leading to loss of brake response?

Steering wheel play should NOT exceed ____ degrees.

You are checking your steering and exhaust systems during a pre-trip inspection. Which of these statements is true?

Which of these keeps your vehicle from rolling when it's parked?

If the examiner asks you to check the coolant level, you should NOT

What should you check to be sure it is solid, clear of objects, and securely bolted to the tractor frame?

Which of the following can disengage the engine from the drivetrain?

More topic

Questions people ask

Official sources

Keep going

Your license is one lesson closer.