ASE T8 Preventive Maintenance Inspection (Medium/Heavy Truck) cheat sheet

FMCSA out-of-service criteria: brake defects at 20% or more of a vehicle's brakes (by pushrod stroke or lining condition) place the vehicle out of service.

A driver must place a vehicle out of service when a defect meets the North American Standard Out-of-Service Criteria and must not operate it until repaired.

Wheel chocks must be placed before any inspection performed under a raised or unsecured vehicle; never work under a load supported only by a jack.

Lockout/tagout: the energy source must be isolated, locked, and the key retained by the person performing the repair before work begins.

PPE minimum for under-vehicle work: eye protection, gloves, and steel-toe footwear; hearing protection is required at or above 85 dBA TWA.

A CDL holder must report any traffic conviction to the employer within 30 days; suspensions must be reported before the end of the business day.

Annual inspection records must be retained for 14 months, and the inspection sticker must be legible and current on the vehicle.

Hazardous material placards must match the material actually loaded; an empty but uncleaned tank retains its placard.

The DVIR is required daily for each vehicle operated; the driver signs it, and the carrier must certify corrective action before the vehicle is re-dispatched.

A DVIR defect must be described in writing on the report; a carrier may not require a driver to operate a vehicle with a known safety defect.

The periodic (annual) inspection must be performed at least once every 12 months by a qualified inspector and documented by a report.

Brake inspection records must include the inspector's name, the date, and the identification of the vehicle inspected.

The vehicle identification number on the inspection report must match the VIN plate on the vehicle; a mismatch invalidates the record.

Odometer readings on service records should be recorded at each inspection to establish the maintenance interval baseline.

A repair order must show the complaint, the cause found, and the correction performed for each documented defect.

Records of driver vehicle inspections must be retained for at least three months from the date of the report.

Hood latch and safety catch must engage fully; the secondary catch must hold the hood if the primary latch releases.

Cab mounts and isolators should be checked for cracks, elongation, and missing bolts; loose cab mounts cause steering and clutch complaints.

Mirror brackets and glass must be secure and free of cracks in the driver's field of view; a cracked mirror is a defect.

Windshield wiper blades that streak or leave unwiped areas must be replaced; washer nozzles must direct fluid onto the glass.

Hood-to-cowl gap and hinge wear are checked by opening and closing the hood while watching for binding or misalignment.

Cab air suspension and cab shock absorbers are inspected for leaks, torn boots, and loose fasteners.

Door hinges, latches, and strikers must hold the door closed against the secondary latch; a door that opens under load is a defect.

Heater and defroster must deliver air to the windshield; a defroster that fails to clear the glass is an out-of-service item in cold weather.

Battery load test: a battery that falls below 9.6 volts during a 15-second load at one-half CCA is defective at 70 degrees F.

Parasitic draw above about 50 mA after all modules sleep indicates a fault; measure with an ammeter in series at the negative post.

Charging system: alternator output should be within about 0.5 volt of the regulator setpoint, typically 13.8 to 14.4 volts at 12V nominal.

Voltage drop testing is done under load; more than 0.5 volt drop on a ground or power circuit indicates excessive resistance.

Starter circuit diagnosis: check battery state of charge, then cranking voltage at the starter terminal; below 9.5 volts during crank suggests cable or battery fault.

J1939 data bus requires 60 ohms across CAN high and CAN low at the diagnostic connector with the key off.

LED lamp retrofit can trigger lamp-out warnings; check for the correct resistor or programmed module setting.

Fuses are rated to protect the wiring, not the load; never increase fuse rating to stop a recurring blow.

Clutch free play is measured at the pedal or release bearing; excessive free play or a dragging clutch produces hard shifting.

Driveline phasing: U-joint yokes on a two-piece shaft must be in phase or vibration will occur at road speed.

Differential lubricant level is checked at the fill plug with the vehicle level; the fluid should be at the bottom of the fill hole.

Transmission and rear axle breathers must be open and routed above the water line to prevent water ingestion.

Engine mounts and transmission mounts are checked for separation, sag, and loose fasteners under torque load.

Driveshaft runout and U-joint play are checked with the shaft rotated by hand and the parking brake released.

Coolant in the engine oil or oil in the coolant indicates a failed oil cooler, head gasket, or liner seal and must be diagnosed before service.

Automatic transmission fluid is checked at operating temperature with the engine running in the specified range on the dipstick.

Frame rails and crossmembers are inspected for cracks, especially at bracket and weld locations; a cracked frame member is a structural defect.

Fifth wheel jaw wear and locking are checked by coupling and tug-testing; the release handle must be secured by the safety latch.

Sliding fifth wheel and tandem locks must be fully engaged; verify by attempting to move the vehicle with the brakes applied.

Air tank drain valves must be opened to purge moisture; a tank that accumulates water indicates a dryer or compressor fault.

Fuel tank straps, mounts, and lines are checked for chafing, leaks, and security; a leaking fuel line is an out-of-service defect.

Mud flaps and splash guards must be present and secure to control spray and debris.

Exhaust system hangers and clamps must support the system without leaks; a leaking exhaust ahead of the cab is a carbon monoxide hazard.

Landing gear must crank freely and lock; bent legs or a stripped crank gear are defects.

Steering free play at the rim of a 20-inch wheel should not exceed about 2 inches; measure with the wheels straight ahead.

Air brake pushrod stroke is measured with the brakes applied at full pressure and compared with the slack adjuster limit for the chamber size.

Automatic slack adjusters that fail to maintain adjustment within limits must be replaced, not repeatedly readjusted.

Brake lining minimum is 1/4 inch (6 mm) at the shoe center for air drum brakes; less is an out-of-service condition.

Air system leak test: with the engine off and brakes applied, pressure loss should not exceed 3 psi per minute for a single vehicle.

Air compressor build-up: the system should build from 85 to 100 psi within about 45 seconds at governed engine speed.

Leaf spring inspection: cracked or missing leaves, broken center bolts, and loose U-bolts are defects; U-bolts are checked for torque.

Air bag suspension: inspect for chafing, cracks, and leaks; a bag that leaks down overnight is defective.

Steering linkage: tie rod ends, drag links, and kingpins are checked for play with the wheels on the ground and an assistant turning the wheel.

Engine oil is checked with the engine off and level; the level should be between the add and full marks, never overfilled.

Coolant freeze point should be tested with a refractometer; a 50/50 mix protects to about -34 degrees F.

Diesel exhaust fluid must meet ISO 22241; contaminated DEF causes derate and aftertreatment faults.

Fuel filter water separators must be drained daily; water in the fuel system damages the high-pressure pump.

Oil analysis intervals are set by hours or miles; trending iron, copper, and silicon identifies wear and dirt ingestion.

Grease fittings on steering, suspension, and driveline should be purged until clean grease appears, without over-pressurizing seals.

Air filter restriction is checked with a gauge; do not clean paper elements, and replace when restriction reaches the manufacturer's limit.

Automatic transmission and power steering fluid levels are checked at operating temperature per the manufacturer's procedure.