California CDL Combination Vehicles Practice Test

The California CDL Combination Vehicles test is a multiple-choice knowledge test you take for your commercial learner's permit. You need at least 80% to pass. That's the federal minimum in 49 CFR 383.135 (California does not publish its own number).

Last updated Oct 7, 2026. FirstTry CDL is a CDL permit test prep site by Hive Asset Group, LLC.

By Scott Wilder, Editor

Last reviewed against the California CDL manual on October 7, 2026

Scott Wilder on X | scottwilderhq.com

FirstTry CDL is a CDL permit test prep site by Hive Asset Group, LLC. It offers free exam-style practice tests built from the official CDL manual. FirstTry CDL is not affiliated with any DMV, FMCSA or government agency. Practice questions are exam-style questions built from the official CDL manual, not actual test questions.

California CDL permit facts

What	What California says	Source
Combination Vehicles pass mark	At least 80%. This is the federal minimum (49 CFR 383.135); California does not publish its own number.	Official page
CLP fee	No separate CLP fee is listed. You pay the nonrefundable application fee ($100 for Class A or B, $59 for Class C commercial) when you apply, good for 12 months	Official page
CLP validity	Up to 180 days from issue. It can be renewed for another 180 days if the expiration is not more than one year from the first application date	Official page
CLP holding period	Hold the CLP at least 14 days before the skills test	Official page
Test languages	The DMV commercial handbook (2019 edition) says commercial knowledge tests are offered in English, Arabic, Chinese, Punjabi, Russian and Spanish. Skills tests must be done in English and interpreters are not allowed. No English-only rule for commercial knowledge tests was found on dmv.ca.gov as of October 2026.	Official page

20 question Combination Vehicles practice test

1. How far should you raise the landing gear before you drive?
1. A. Just enough to clear the pavement
2. B. Halfway, so it can drop if needed
3. C. All the way up
4. D. It does not matter when the trailer is loaded
Show answer
Answer: C. All the way up
Landing gear left part way up may catch on railroad tracks or other things.
From the official CDL manual, section 6.4.1.
2. You do not hear air escaping from both lines at the rear. What should you check?
1. A. That the trailer wheels are chocked
2. B. That the shut-off valves on the trailers and dollies are open
3. C. That the landing gear is raised
4. D. That the trailer tires are fully inflated
Show answer
Answer: B. That the shut-off valves on the trailers and dollies are open
Closed valves block the air from reaching the back.
From the official CDL manual, section 6.5.2.
3. Why is it easy to lock up the wheels of a lightly loaded combination?
1. A. The brakes are weaker when the trailer is empty
2. B. Stiff springs and strong brakes give poor traction
3. C. The air tanks hold less pressure when empty
4. D. Empty trailers have too much traction
Show answer
Answer: B. Stiff springs and strong brakes give poor traction
Little weight on very stiff springs and strong brakes means poor traction, so wheels lock easily.
From the official CDL manual, section 6.1.3.
4. When you connect the air-lines, which line goes to the trailer emergency glad hand?
1. A. The tractor service air-line
2. B. The tractor parking line
3. C. The electrical cord
4. D. The tractor emergency air-line
Show answer
Answer: D. The tractor emergency air-line
The tractor emergency air-line connects to the trailer emergency glad hand, after you check the seals.
From the official CDL manual, section 6.4.1.
5. How often should you drain each trailer air tank?
1. A. Once a week
2. B. Every day
3. C. Once a month
4. D. Only when the brakes feel weak
Show answer
Answer: B. Every day
Draining daily keeps water and oil from building up.
From the official CDL manual, section 6.2.6.
6. Before coupling, how should the fifth wheel be tilted?
1. A. Up toward the cab
2. B. Level with the frame
3. C. Down toward the rear of the tractor
4. D. Sideways to the left
Show answer
Answer: C. Down toward the rear of the tractor
The manual says the fifth wheel should be tilted down toward the rear of the tractor.
From the official CDL manual, section 6.4.1.
7. Why shut the engine off when checking for crossed air-lines after supplying air to the trailer?
1. A. To keep the compressor from overheating
2. B. To keep the trailer air tanks from overfilling
3. C. To close the tractor protection valve
4. D. So you can hear the trailer brakes apply and release
Show answer
Answer: D. So you can hear the trailer brakes apply and release
You should hear the brakes move when applied and air escape when released.
From the official CDL manual, section 6.4.1.
8. After you inspect the coupling, what do you do with the electrical cord?
1. A. Leave it hanging loose
2. B. Plug it into the trailer and fasten the safety catch
3. C. Tie it to the landing gear
4. D. Connect it to the air-line
Show answer
Answer: B. Plug it into the trailer and fasten the safety catch
The cord is plugged into the trailer and the safety catch is fastened.
From the official CDL manual, section 6.4.1.
9. Which of these trailers can get stuck on a raised railroad crossing?
1. A. A tall, box-style dry van with high ground clearance
2. B. A short flatbed with large wheels
3. C. A low slung unit such as a lowboy or car carrier
4. D. A tractor with no trailer
Show answer
Answer: C. A low slung unit such as a lowboy or car carrier
The manual lists low slung units like lowboys, car carriers, moving vans and possum-belly livestock trailers.
From the official CDL manual, section 6.1.4.
10. Which two names are other names for the trailer hand valve?
1. A. Relay valve and trolley valve
2. B. Johnson bar and cut-out cock
3. C. Trolley valve and Johnson bar
4. D. Dolly valve and Johnson bar
Show answer
Answer: C. Trolley valve and Johnson bar
The manual lists trolley valve and Johnson bar as other names for the trailer hand valve.
From the official CDL manual, section 6.2.1.
11. On a sliding fifth wheel, what should you check about the locking pins?
1. A. They are all removed to let it slide
2. B. All are present and locked in place
3. C. Some may be missing if the others are tight
Show answer
Answer: B. All are present and locked in place
All locking pins must be present and locked in place.
From the official CDL manual, section 6.5.1.
12. What does the trailer air supply control look like on newer vehicles?
1. A. A red eight-sided knob
2. B. A blue round knob
3. C. A yellow diamond-shaped knob
4. D. A black T-handle
Show answer
Answer: A. A red eight-sided knob
The manual describes it as a red eight-sided knob.
From the official CDL manual, section 6.2.3.
13. What happens when you pull out the trailer air supply control?
1. A. Air is supplied to the trailer
2. B. The trailer service brakes release
3. C. The tractor parking brakes lock
4. D. The air is shut off and the trailer emergency brakes come on
Show answer
Answer: D. The air is shut off and the trailer emergency brakes come on
Pulling the knob out shuts off the trailer air supply and applies the emergency brakes.
From the official CDL manual, section 6.2.3.
14. Compared with an empty rig, how likely is a fully loaded rig to roll over in a crash?
1. A. Ten times as likely
2. B. Twice as likely
3. C. About the same
4. D. Less likely, because the weight holds it down
Show answer
Answer: A. Ten times as likely
The manual says a fully loaded rig is ten times more likely to roll over in a crash than an empty one.
From the official CDL manual, section 6.1.1.
15. Only your trailer has ABS. How does this affect your control during braking?
1. A. It gives you no extra control
2. B. It gives you more control
3. C. It makes the brakes weaker
Show answer
Answer: B. It gives you more control
ABS on only the trailer, or only one axle, still gives you more control.
From the official CDL manual, section 6.3.2.
16. You connect the air and electrical lines. What must you make sure of?
1. A. They are as long as possible
2. B. They are painted the same color
3. C. They are hidden under the trailer
4. D. They will not hit any moving parts
Show answer
Answer: D. They will not hit any moving parts
The lines must not hit any moving parts of the vehicle.
From the official CDL manual, section 6.4.1.
17. Before coupling, where should the safety unlocking handle of the fifth wheel be?
1. A. In the open position
2. B. In the automatic lock position
3. C. Removed from the fifth wheel
4. D. In the release position
Show answer
Answer: B. In the automatic lock position
The fifth wheel must be ready for coupling with the handle in the automatic lock position.
From the official CDL manual, section 6.4.1.
18. What is the earliest and best way to see that your trailer has started to skid?
1. A. Feel the steering wheel go light
2. B. Hear the trailer tires squeal
3. C. See it in your mirrors
4. D. Watch the trailer air gauge
Show answer
Answer: C. See it in your mirrors
Check the mirrors any time you brake hard.
From the official CDL manual, section 6.1.5.
19. Cargo is loaded toward one side and makes the trailer lean. What is the result?
1. A. The trailer tracks better in turns
2. B. A rollover is more likely
3. C. Braking distance gets shorter
4. D. Nothing, if the weight is within legal limits
Show answer
Answer: B. A rollover is more likely
A load off to one side makes the trailer lean, which makes a rollover more likely.
From the official CDL manual, section 6.1.1.
20. In Step 9 of coupling, what do you do to lock the trailer brakes?
1. A. Push in the "air supply" knob
2. B. Pull out the "air supply" knob
3. C. Put the transmission in neutral
4. D. Raise the landing gear
Show answer
Answer: B. Pull out the "air supply" knob
Pulling out the "air supply" knob locks the trailer brakes.
From the official CDL manual, section 6.4.1.

California CDL Combination Vehicles questions

What score do you need to pass the California CDL Combination Vehicles test?

You need at least 80% to pass. That is the federal minimum in 49 CFR 383.135. California does not publish its own number.

Is the California CDL Combination Vehicles test the same as other states?

The Combination Vehicles test is built on the same federal knowledge standards in every state, so the topics match the CDL manual. California uses its own handbook: https://www.dmv.ca.gov/web/eng_pdf/comlhdbk.pdf

How much does a CDL permit cost in California?

CLP fee: No separate CLP fee is listed. You pay the nonrefundable application fee ($100 for Class A or B, $59 for Class C commercial) when you apply, good for 12 months.

What languages is the California CDL knowledge test offered in?

The DMV commercial handbook (2019 edition) says commercial knowledge tests are offered in English, Arabic, Chinese, Punjabi, Russian and Spanish. Skills tests must be done in English and interpreters are not allowed. No English-only rule for commercial knowledge tests was found on dmv.ca.gov as of October 2026.

Sources

https://www.ecfr.gov/current/title-49/section-383.135
https://www.dmv.ca.gov/portal/driver-licenses-identification-cards/licensing-fees/
https://www.dmv.ca.gov/portal/driver-licenses-identification-cards/commercial-driver-licenses-cdl/
https://www.dmv.ca.gov/web/eng_pdf/comlhdbk.pdf
Manual sections used in this test: 6.1.1; 6.1.3; 6.1.4; 6.1.5; 6.2.1; 6.2.3; 6.2.6; 6.3.2; 6.4.1; 6.5.1; 6.5.2

Combination Vehicles practice test in nearby states