Tractor and Trailer Preventive Maintenance Inspection

Pull the unit from the fleet record in Fleetio or your TMS and confirm VIN matches the door jamb and dash plate. Mismatches usually mean a glider kit or a swapped frame — flag for the maintenance coordinator before continuing.

Record both odometer and ECM engine hours — PM intervals on long-idle units (reefer power, sleeper APUs missing) come due on hours well before mileage. Log to the unit's PM history.

Part 396.17 annual inspection — sticker must show inspection within the last 12 months. If within 60 days of expiry, schedule the annual at this PM rather than letting it lapse mid-route.

Confirm registration, cab card (IRP), insurance card (COI), and current medical certificate copy are in the document pouch. A driver pulled at roadside without these gets the unit OOS regardless of mechanical condition.

With engine off and air built to governor cut-out, fan the brakes. Low-air warning (buzzer and dash light) must activate at or above 60 psi per Part 393.51. Continue fanning — spring brakes (yellow knob) should pop out between 20 and 45 psi.

Open the Motive or Samsara unit, confirm cable seated to the J1939 port, and pull the last 14 days of driver logs. Note any unresolved HOS violations or unassigned driving time — these need annotation and driver acknowledgment before the unit leaves the yard.

Cycle the key to bulb-check all dash warning lamps including ABS, MIL, DPF, and stability control. A burned-out MIL bulb hides an active engine fault — common gotcha on older Cascadias and 579s.

Walk the tractor with another tech or use the cab kick-down to cycle lights. Per Part 393.11, all required lamps must be operational and the correct color. A single inop marker is a citation; two on the same side is an OOS condition on roadside.

Steers require ≥4/32" tread across all major grooves (Part 393.75). Check pressure cold against the sidewall spec — typically 110-120 psi for 295/75R22.5. Note any sidewall bulges, exposed cord, or sidewall damage as OOS conditions.

Crawl under and verify the jaw is fully closed around the kingpin with no gap between trailer apron and fifth-wheel plate. Grease the plate if dry — high-hitch and low-hitch issues here cause the trailer to drop and are the most frequent yard incident.

Look for chafe, cuts, and audible air leaks at the gladhand seals. Replace cracked rubber gladhand seals — a $2 part that prevents a service-air leak that pulls the trailer out of service at a scale.

Engine off and cold. Oil on the full mark, coolant at the cold-fill line, DEF tank above ¼. A low DEF tank derates the truck below 5 mph within 30 miles — log a top-off, don't just note it.

Look for cracks on the underside of serpentine belts, swelling at hose ends, and coolant weeping at clamps. Spin the fan by hand — bearing roughness is a precursor to a thrown fan blade through the radiator.

Resting voltage ≥12.6 V across the bank; under load (cranking) should not drop below 9.6 V. Clean any green corrosion at the terminals and check tie-down bolts — loose batteries arc and start fires in the box.

Pull the soot load and ash load via the OEM scan tool (DDDL for Detroit, ServiceMaxx for Navistar, Insite for Cummins). High soot with no recent active regen indicates a stuck EGR valve or failed DOC — these turn into a parked regen call from the side of the highway.

With 90-100 psi applied, mark the pushrod and measure stroke. CVSA OOS criteria: 20% of brakes at or beyond adjustment limit. Type 30 long-stroke limit is 2.5"; standard is 2". Auto-slack adjusters that need manual adjustment are a defective slack adjuster, not a fix — replace, don't crank.

Lining ≥¼" at the thinnest point, drums free of heat cracks through to the friction surface, no contamination from a leaking wheel seal. A blue-heat-cracked drum is OOS and will not pass a CVSA Level 1.

Walk the suspension: any broken or shifted main leaf is OOS, any deflated air bag or torn bellows replaces. Shock absorbers leaking oil down the body are spent — note for replacement at the next interval.

Pry-bar test each U-joint for play — any perceptible movement is a replacement, not a wait-and-see. Confirm slack adjusters are the same brand and length on each axle; mixed Haldex and Bendix on one axle is a common scrapyard-replacement gotcha.

Capture the trailer number for the DVIR. Equipment type drives which downstream checks apply — reefer units add the temperature-control inspection, flatbeds add load-securement hardware.

Trailer tread minimum ≥2/32" per Part 393.75. Aluminum rims: look for cracks at the bolt holes radiating outward — the failure mode is sudden. Mud flaps must extend to within 6" of the ground unloaded.

Hook a light tester to the pigtail or have a tech apply brake and signal from the cab. Corroded 7-pin sockets are the single most common trailer-light DOT violation — clean and dielectric grease them, don't just wiggle the connector until lights come on.

Crank landing gear through both high and low gears — gritty or stuck gearboxes need pulling and regreasing. On air-ride trailers, confirm the dump valve and height-control valve work; a stuck-high trailer eats kingpins and shears bolts on the fifth wheel.

Thermo King or Carrier — pull the last 7 days of temperature trace from the download port and confirm no excursions. Fuel tank ≥¾ before dispatch on multi-day loads; a reefer that shuts down on a frozen load is a full-trailer claim.

Hang the red OOS tag in the cab, lock the keys in the shop key box, and notify the fleet maintenance coordinator and dispatch in the same message so no one re-assigns the unit. Log the OOS reason and CVSA cite in Fleetio against the unit record.

Per Part 396.11, every defect found during this PM goes on the written DVIR — even items repaired during the inspection. Honest defect history is the carrier's defense in a post-accident plaintiff subpoena; the cheap fix is writing it down.

Tech signs the inspection; fleet maintenance coordinator counter-signs after reviewing the DVIR and brake stroke result. File the signed PM in the unit's maintenance folder — required retention is 12 months under Part 396.21.