ASE T-Series study guide
ASE T-Series · Work through your exam, one topic at a time.
ASE T-Series refers to the Medium/Heavy Truck certification tests offered by the National Institute for Automotive Service Excellence (ASE), an organization that certifies automotive service professionals across the country. The T-Series is aimed at technicians who diagnose, service, and repair medium- and heavy-duty trucks - work found in dealerships, independent shops, fleets, and transit and municipal garages. The ASE T-Series study guide has 8 sections and about 2,379 words.
01Gasoline Engines
Every gasoline no-start or driveability complaint reduces to four basics: air, fuel, spark, compression . Know the four-stroke cycle (intake, compression, power, exhaust), the difference between port injection and direct injection, and how coil-on-plug ignition uses crank and cam signals to sequence spark.
314 words, about 2 min02Diesel Engines
Diesel ignition is by heat of compression alone, typically 16:1 to 18:1, so cranking speed, ring sealing, and valve sealing matter more than spark. Understand injection pressure and timing, and the major fuel system families: mechanical (inline or rotary pump), unit injector, HEUI (hydraulically actuated, oil pressure driven), and common rail.
299 words, about 1 min03Drive Train
Trace power from flywheel to tire: clutch or torque converter, transmission (manual, automated manual, or automatic), driveshaft and U-joints, differential ring and pinion, axles, and wheels. Know clutch adjustment and free play, release bearing and pilot bearing symptoms, and the difference between a slipping clutch (rpm rises without vehicle speed) and a dragging clutch (hard shifting, gear clash).
311 words, about 2 min04Brakes
Follow the air path: compressor → governor → air dryer → supply and primary/secondary reservoirs → foot valve → relay valve → brake chambers, with spring (parking) brakes applied by released air pressure. Know typical governor cut-out near 125 psi and cut-in near 100 psi, low-pressure warning by 60 psi, and the pressure-protection valve that preserves supply pressure for the parking brakes.
327 words, about 2 min05Suspension and Steering
Understand leaf springs, air suspension with height-control valves, shock absorbers (they control motion, not load), kingpins and ball joints, tie rods, drag links, steering gears, and power steering pumps. Know the alignment angles: caster (steering axis tilt, affects returnability and lead/pull), camber (wheel lean, affects one-sided wear), toe (total and individual, the primary tire-wear angle), and thrust angle (rear axle alignment relative to the frame).
260 words, about 1 min06Electrical/Electronic Systems
Start with Ohm's law (E = I × R) and the two families of measurement: resistance (component isolated, power off) and voltage drop (circuit loaded and operating). Voltage drop is the technician's best tool because it tests the circuit under real current.
307 words, about 2 min07Heating, Ventilation, and Air Conditioning (HVAC)
Know the refrigeration cycle: compressor raises pressure and temperature, condenser rejects heat, expansion device drops pressure, evaporator absorbs heat. Identify system hardware - compressor and clutch, condenser, receiver-drier (expansion-valve systems) or accumulator (orifice-tube systems), expansion valve or orifice tube, evaporator, blower, blend door, and heater core.
276 words, about 1 min08Preventive Maintenance Inspection (PMI)
PMI is a documented, systematic inspection: walk-around, under-hood, under-vehicle, and operational checks. Know the DOT annual inspection requirement, CVSA out-of-service criteria, and the difference between a maintenance inspection and a federally required annual inspection - the annual inspection must be performed and documented by a qualified inspector.
285 words, about 1 min