Pre-Trip Inspection Study Guide
Pre-Trip Inspection is the only CDL skill that's tested verbally rather than in writing. You don't take it on a computer at the DMV; you take it standing next to a truck with an examiner watching. You'll walk around the vehicle, point to specific components, and explain what you're inspecting and what you're looking for. The examiner is grading you on whether you can demonstrate that you can do a thorough inspection on your own.
Because there's no written test, this guide is structured around what you'll actually be tested on at the DMV — the components, the order, and the language to use. Memorizing this material thoroughly is the difference between passing on the first attempt and a $50 retake fee plus another wait at the DMV.
How the test works
The examiner will hand you a list of inspection categories. Different states use different category breakdowns, but the typical structure is:
- Engine compartment / front of vehicle.
- In-cab inspection / brake check.
- Driver-side and rear-of-tractor exterior.
- Coupling system (for combination vehicles).
- Trailer (front, side, rear, lights).
- Air brake check (the seven-step test).
For each category, you'll walk to the components in that area, point to each one, and verbalize what you're checking. The examiner doesn't expect you to memorize every part of every system — but they do expect you to demonstrate consistent inspection technique and to use the right terminology.
The phrases that matter
Examiners listen for specific phrases. Learning the standard inspection language is half the battle. For most components, you're checking for some combination of:
- Mounted securely. The part is firmly attached and not loose.
- Not bent, broken, cracked, or missing. Physical condition.
- Not leaking. No fluids visible where they shouldn't be.
- Properly adjusted. For things like belts, slack adjusters, and mirrors.
- Functions properly. For things you can test, like horns and lights.
For every component, walk through the relevant items. For example, on a steering tire: "Tire is mounted securely, no missing or damaged lug nuts, sidewall is not cut or cracked, tread depth is at least 4/32 of an inch, no objects between the duals" (if applicable), "valve stem and cap are present, properly inflated."
Engine compartment walkthrough
Open the hood. Some buses have engine access from the rear or side; for tractors, it's the standard front hood. Identify:
- Engine oil level. Check the dipstick, between min and max marks.
- Coolant level. In the radiator or expansion tank.
- Power steering fluid. Reservoir, level between marks.
- Windshield washer fluid.
- Belts. Alternator belt, water pump belt — check tension (no more than 3/4 inch deflection), no cracks, no fraying.
- Hoses. Radiator hoses, heater hoses — no leaks, no cracks, no soft spots, secure clamps.
- Wiring. No exposed wires, no loose connections.
- Steering box and hoses. Mounted securely, hoses not leaking.
- Steering linkage. Pitman arm, drag link, tie rod — no cracks, no missing nuts, cotter keys in place.
- Front suspension. Springs not cracked, shocks not leaking, U-bolts tight.
- Front brakes. Brake chamber, pushrod, slack adjuster — no cracks, free play less than one inch on slack adjuster, brake hoses not chafing.
- Front wheel and tire. See tire-specific items above.
In-cab and brake check
After the engine compartment, you typically move into the cab to check controls and instruments, then perform the air brake check. The seven-step air brake test is:
- Governor cut-out (~125 psi) and cut-in (~100 psi).
- Air leakage rate, engine off, brakes released — no more than 2 psi/min single, 3 psi/min combination.
- Air leakage rate with brake fully applied — no more than 3 psi/min single, 4 psi/min combination.
- Low pressure warning at 60 psi.
- Spring brake activation between 20 and 45 psi.
- Air pressure buildup from 85 to 100 psi within 45 seconds (dual systems).
- Service brake test in motion.
Memorize these numbers. Examiners will ask you to recite them.
Common failure points
The most common reasons applicants fail Pre-Trip Inspection:
- Skipping a category entirely.
- Not pointing to the component you're naming. The examiner needs to see you physically identify it.
- Using vague language like "this looks okay" instead of specific inspection terminology.
- Forgetting the air brake check numbers.
- Going out of order in a way that suggests you're guessing.
- Not verbalizing. Even if you're inspecting correctly, the examiner needs to hear you say what you're checking. Silent inspection fails.
Practice approach
The best preparation is repetition with an actual truck. CDL schools spend significant time on Pre-Trip practice for this reason. If you have access to a vehicle, walk through the inspection out loud, even if no one is grading you. Get comfortable narrating what you're doing.
If you're studying outside a CDL school, watch examiner-style YouTube videos where instructors walk through complete inspections. Pause, repeat the language, and visualize doing it on a real truck. Many CDL schools provide written checklists matching their state's exam — those are gold if you can get one.
The rest of the CDL written exam
While Pre-Trip is verbal, every other CDL section is a written multiple-choice test you can practice for online. Use our free practice tests to prepare for those: