California CDL Combination Vehicles Test study plan

List every inspection item in the CDL combination-vehicle walk-around sequence from memory, in correct order

Explain how a tractor protection valve and trailer air supply valve interact during normal operation and during a breakaway

Identify the three braking systems on a combination vehicle (service, parking, emergency) and state what each one does

Label a hand-drawn air brake system diagram showing compressor, governor, tanks, and valves

Perform a full pre-trip inspection aloud in under 20 minutes, narrating each item and its defect criteria

Describe the low air pressure warning test and the tractor protection valve pop-out test step by step

Explain how to check for air leaks with the engine off and state what rate of loss is acceptable

Demonstrate the tug test and state why it is done before pulling out

Practice straight-line backing, offset backing, and alley docking with a combination vehicle or simulator

Explain how pivot points and off-tracking change when a trailer is added

Describe how to recover from a jackknife-prone braking situation using controlled stab braking

State the correct braking technique for downhill grades with a combination vehicle

Sequence the coupling procedure in correct order from memory, including the pre-coupling inspection

Explain the three-point stance and the visual check for kingpin lock engagement

Describe how to test the fifth-wheel release with the tractor brakes set

Explain why the trailer spring brakes must be set during coupling and what happens if they are not

Sequence the uncoupling procedure in correct order, including landing gear and air line removal

Explain why the trailer brakes must be set before releasing the fifth-wheel jaw

Demonstrate the coupling and uncoupling sequence on a vehicle or simulator while narrating each step

Identify common coupling failures such as high hook, missed kingpin, and crossed air lines

Explain how to adjust following distance for a combination vehicle at highway speed and in poor conditions

Describe how to control speed on a downgrade before the descent begins

Explain how to check mirrors and manage blind spots when changing lanes with a trailer

Describe the correct response to a trailer brake failure or a trailer breakaway

Describe how to handle a tire blowout on a combination vehicle without hard braking

Explain how to recover from a trailer skid and why locking the drive wheels causes jackknifing

Plan a route that avoids low clearances, tight turns, and steep grades, and explain each avoidance

Explain how to use turn signals, hazard lights, and horn appropriately with a long combination vehicle

Complete a full-length practice test covering all four domains and score 90% or higher

Review every missed question and write the correct reasoning for each

Re-run the full pre-trip inspection and coupling/uncoupling sequences under timed conditions

State the top five personal weak areas and the specific corrective action for each