CDL Pre-Trip Inspection
The pre-trip inspection is the part of the CDL skills test most people fail, and it fails them for an unexpected reason: it is a spoken test. You walk the vehicle and say what you are checking, from memory, in front of an examiner. Knowing the truck is not enough — you have to narrate it.
The seven-step walk
- Vehicle overview. Approach, general condition, leaks under the vehicle, paperwork.
- Engine compartment. Fluid levels, belts, hoses, wiring, the components you can name.
- In-cab. Start it, check the gauges, safety equipment, mirrors, windscreen, controls.
- Driver-side walk-around. Door, mirror, suspension, brakes, tyres, wheels, lights.
- Rear of vehicle. Splash guards, lights and reflectors, cargo securement, doors.
- Passenger-side walk-around. The same sequence as the driver side, in reverse.
- Air brake check and light check. The scored sequence below.
One phrase does most of the work
For every metal part you point at, the examiner is listening for the same four things: that it is securely mounted, not cracked, bent or broken. For anything carrying fluid or air: no leaks, no cuts, no bulges, properly connected. Two phrases, repeated across the whole vehicle. Candidates who invent fresh wording at every part run out of it and go quiet, and silence scores nothing.
The air brake check is the scored sequence
This is where points are actually lost, because it is a fixed procedure with numbers in it:
- Leak test. Engine off, key on, parking brakes released. Hold the foot brake one minute. Loss must not exceed 4 psi for a combination vehicle, 3 psi for a straight truck.
- Warning devices. Fan the brakes down — the low-air warning light and buzzer must activate before pressure falls below 60 psi.
- Spring brake pop-out. Keep fanning; the parking brake valves must pop out by around 20 to 45 psi.
- Build-up rate. Restart and confirm pressure builds from 85 to 100 psi within 45 seconds.
Say the numbers aloud as you hit them. The examiner is scoring what you demonstrate you know, not what you happen to be looking at.
Practise the knowledge behind it
The inspection questions on the written test cover the same components, and the air brake numbers above are the ones the air brakes test asks about:
- General knowledge practice test — includes inspection
- Air brakes practice test — the psi numbers and warning devices
Exact scoring varies by state and by the vehicle you bring. Confirm the current requirements with your state licensing agency and your training provider.
More CDL guides
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Frequently asked questions
What do you say during a CDL pre-trip inspection?
For metal parts: securely mounted, not cracked, bent or broken. For anything carrying air or fluid: no leaks, no cuts, no bulges, properly connected. Those two phrases cover most of the vehicle, repeated at each component.
How much air pressure loss is allowed in the leak test?
No more than 4 psi in one minute for a combination vehicle, or 3 psi for a straight truck, with the engine off, key on and parking brakes released.
At what pressure must the low-air warning come on?
Before pressure drops below 60 psi. Keep fanning and the spring brake valves should pop out at roughly 20 to 45 psi.
