The pre-trip inspection is the first part of your CDL skills test. It's also the part most people underestimate. You're expected to walk through the entire vehicle, identify every major component, explain what you're checking and why, and correctly assess whether the vehicle is safe to operate — all from memory.
Here's the full sequence and what the examiner is looking for at each step.
Why the Pre-Trip Matters Beyond the Test
Federal regulations require CDL drivers to perform a pre-trip inspection before every trip. It's not a box-checking exercise — it's a legal requirement. Missing a defect during a pre-trip, then having that defect cause an accident, can result in personal liability, license suspension, and federal citations.
Inspectors at weigh stations also conduct roadside inspections. If your vehicle has a defect that should have been caught during a pre-trip, you can receive an out-of-service order and citations even if you didn't cause the defect.
The Sequence — Engine Compartment
Start at the driver's side front of the vehicle before opening the hood.
Check that the parking brakes are on and the vehicle is in neutral. Then open the hood or tilt the cab (on cab-over designs).
In the engine compartment, you're checking: engine oil level, coolant level in the overflow reservoir, power steering fluid, windshield washer fluid, battery (security, connections, no cracks or corrosion), alternator belt condition and tension, all belts for fraying and proper tension, hoses for cracks or leaks, and the overall condition of the engine compartment for leaks.
The examiner expects you to physically point to and name each component while stating what you're checking for. "I'm checking the oil level — it's between the add and full marks, no leaks visible."
Cab Inspection
Enter the cab. Check:
Gauges: oil pressure (should build within seconds of startup), temperature, ammeter/voltmeter, air pressure gauges (dual system — both should read 90-120 psi). Warning lights and buzzers — all should go out as the engine warms and air pressure builds.
Mirrors: properly adjusted, not cracked, secure.
Steering wheel: no excessive play (no more than 10 degrees or 2 inches at the rim for vehicles with power steering).
Windshield: no cracks, defroster works, wipers work and blades are in good condition.
Safety equipment: fire extinguisher (charged and accessible), emergency triangles (three), first aid kit, spare fuses if applicable.
Seat belt: functional, properly latches.
Horn: works.
Walk-Around — Left Side (Driver's Side)
Exit the cab and begin the exterior walk-around.
Left front: check the tire (inflation, tread depth, sidewall condition, valve stem), the hub and lug nuts (tight, no rust trails indicating loose nuts, no missing lugs), the wheel seal (no grease on wheel), brake components visible through the wheel (brake drum condition, brake lining thickness, S-cam area), and the steering components (tie rod, drag link, kingpin).
Left fuel tank: mounted securely, cap on and tight, no leaks, not overfull.
Left rear tires: same checks as front, but look for dual tires — they should be the same size and inflation, not touching each other, with adequate space between them.
Left rear lights: clearance lights, brake lights, turn signals — check with the lights on.
Walk-Around — Rear of Vehicle
Rear lights and reflectors: all required lights present and functional, reflectors clean and in good condition.
Cargo: if loaded, check that cargo is properly secured, doors are latched and locked, mudflaps are present and secure.
On a tractor-trailer: check the trailer connection — kingpin properly coupled into the fifth wheel, fifth wheel jaws closed around the kingpin (try to pull apart by tugging the trailer), air lines connected and not kinked or rubbing, electrical connector plugged in and latched, trailer height appropriate (not too high for the fifth wheel to support).
Walk-Around — Right Side (Passenger Side)
Mirror the left side check. Every component you checked on the left gets checked on the right. Most people rush this side because they've already done one side — the examiner knows this and pays attention.
Signal Check
Return to the cab. Turn on left turn signal, exit the cab and verify left front and rear are flashing. Return to cab, turn on right turn signal, check right front and rear. Test hazards. Test brake lights (have the examiner press the brake pedal while you watch from outside, or ask someone to help).
What Constitutes a Defect
Major defects that would fail a roadside inspection — and should fail your pre-trip — include: tire inflation below minimum, visible tread depth below 4/32" on steering axles or 2/32" on other axles, brake lining below minimum thickness, brake components that are cracked or missing, any fluid leak that's more than a few drops, broken or missing lights required for operation, cracked windshield in the driver's view, and broken or missing safety equipment.
The skills test vehicle should be in proper working order — but the examiner expects you to identify the difference between normal wear and an actual defect.
Our Pre-Trip Inspection practice tests cover engine compartment, cab inspection, lights, brakes, and trailer connections.