Pre-Trip Inspection Checklist for Commercial Diesel Trucks

Begin with a cold engine check when possible. Inspect: engine oil level on level ground. Coolant level in overflow reservoir. Power steering fluid. Windshield washer fluid. Battery connections, secure with no corrosion. Belts for cracks, fraying, or glazing. Hoses for leaks, cracks, or soft spots. Air filter restriction indicator if equipped. Any fluid leaks on the ground under the engine compartment.

Before starting: Check all gauges for correct resting position. Verify mirrors are adjusted. Test horn. Check wipers and washers. Verify all required documents are present: registration, insurance, medical certificate, and logbook or ELD.

After starting: Allow air pressure to build to operating range. Test service brakes. Check for pull or delayed response. Test parking brake by attempting to move the truck with it applied. Check all warning lights extinguish as systems come online. Listen for unusual sounds.

Walk around and verify: headlights, low and high beam. Tail lights. Brake lights. Turn signals at all four corners. Hazard lights. Clearance and marker lights. Reverse lights and audible backup alarm. Trailer lights if applicable, with the plug connection secure and all trailer lights functioning.

Inspect every tire on the truck and trailer. Check: inflation pressure with a calibrated gauge, not by thumping. Tread depth: minimum 4/32" on steering axle tires, 2/32" on all others for FMCSA compliance. Sidewall condition for cuts, bulges, or exposed cords. Valve stems and caps. Lug nut torque, looking for rust streaks or movement indicators. Wheel seals for oil contamination on the inside of wheels indicating hub seal failure.

With air pressure at operating level: check for audible air leaks at all brake chambers, glad hands, and air lines. Drain air tanks and verify automatic drain valves function. Perform a static brake check: build air to 100 psi, shut engine, and observe pressure drop. Loss of more than 3 psi per minute with brakes released (or 4 psi per minute with brakes applied) indicates a significant leak requiring repair before operation.

Visually inspect brake chambers for: push rod travel within adjustment limits, slack adjusters functioning, and brake linings free of contamination, cracking, or wear near minimum thickness.

For tractor-trailer combinations: verify fifth wheel is lubricated. Check that the locking jaw is fully engaged around the kingpin. Attempt to separate the trailer by pulling forward with parking brakes released. Inspect safety chains or cables. Check glad hand connections. Verify trailer landing gear is fully retracted. Confirm cargo is secured and the load does not exceed axle weight limits.