If you service medium- and heavy-duty trucks, the ASE Medium-Heavy Truck (T Series) is the industry standard for proving your skills. Awarded by the National Institute for Automotive Service Excellence (ASE), these credentials show employers and fleet managers that you can diagnose and repair everything from diesel fuel systems to air brakes.

Eight separate tests can feel like a lot to take on. The good news is that ASE publishes a detailed study guide for every test, including exactly how many questions come from each content area.

In this guide, we’ll walk you through the format, all eight tests and their content areas, the official resources worth downloading, and the questions technicians ask most often.

What Is the ASE T Series?

The T Series is not one exam. It includes eight individual certification tests, T1 through T8, each covering one major truck system. You can take them one at a time, in any order, and each one you pass (plus documented work experience) earns its own ASE certification.
Technicians who earn T2 through T8 are recognized as ASE Certified Master Medium-Heavy Truck Technicians. T1 (Gasoline Engines) is not required for Master status, which reflects how diesel-dominated the heavy truck world is.

Questions are written around real shop situations. Rather than asking you to recite a definition, a typical item describes a complaint or an inspection finding and asks for the most likely cause, the next test, or the correct repair.

What Is the ASE T Series Exam Format?

Here are the key facts, based on the ASE T1-T8 test page and the ASE Medium/Heavy Truck Tests Study Guide (2026):

  • Tests: Eight separate tests (T1-T8), purchased and scheduled individually.
  • Scored vs. unscored: Each certification test includes 10 research questions that don’t count toward your score. You won’t know which ones are unscored, so answer every question.
  • Total size: 400 scored questions across all eight tests (465 including research questions), with 600 minutes of combined testing time.
  • Question types: Four-option multiple choice, including standard one-answer items, “Technician A says / Technician B says” items, and EXCEPT items.
  • Delivery: Computer-based at a test center. Online remote testing is offered for recertification tests.
  • Results: Your score report is emailed right after your appointment, and results appear in your myASE account, usually within 24 hours.
  • Passing score: ASE does not publish a fixed passing percentage for the T Series.
  • Fees: $34 registration fee per order plus $62 per certification test, per the ASE registration and fees page.

What Content Outline Does the ASE T Series Use?

The current tests are based on the ASE Medium/Heavy Truck Tests Study Guide, effective 2026. For each test, the guide lists lettered content areas, the number of scored questions from each, and a detailed task list. Here is how each test breaks down.

T1: Gasoline Engines (50 scored questions, 75 minutes)

T1 covers gasoline engines in medium-duty trucks. General diagnosis and electronic controls make up nearly half the test.

  • A. General Engine Diagnosis (14)
  • B. Cylinder Head and Valve Train (4); C. Engine Block (4); D. Lubrication and Cooling Systems (3)
  • E. Ignition System (6); F. Fuel, Air Induction, and Exhaust Systems (6)
  • G. Emissions Control Systems (5); H. Computerized Engine Controls (8)

Study tip: Be comfortable using a scan tool, digital multimeter (DMM), and oscilloscope to diagnose drivability problems with stored or active diagnostic trouble codes (DTCs).

T2: Diesel Engines (55 scored questions, 90 minutes)

T2 is the longest test in the series, and the fuel system alone accounts for 16 questions, including high-pressure common rail (HPCR) diagnosis.

  • A. General Engine Diagnosis (11)
  • B. Cylinder Head and Valve Train (4); C. Engine Block (5); D. Lubrication and Cooling Systems (6)
  • E. Air Induction and Exhaust Systems (6), including turbochargers and aftertreatment
  • F. Fuel System (16); G. Starting and Charging System (4); H. Engine Brakes (3)

T3: Drive Train (40 scored questions, 60 minutes)

T3 follows power from the flywheel to the wheel ends.

  • A. Clutch (11)
  • B. Transmission (13), including electronically controlled and automated manual transmissions
  • C. Driveshaft and Universal Joint (7)
  • D. Drive Axle (9)

What questions look like: A vibration that changes with road speed, not engine speed, points you toward driveshaft balance, U-joint wear, or incorrect phasing.

T4: Brakes (50 scored questions, 75 minutes)

Air brakes dominate this test at 32 of 50 questions.

  • A. Air Brakes (32): air supply and service systems (15), mechanical/foundation brakes and wheel hubs (13), parking brakes (4)
  • B. Hydraulic Brakes (11)
  • C. Antilock Brake System (ABS), Automatic Traction Control (ATC), Electronic Stability Control, and Collision Warning/Avoidance Systems (7)

T5: Suspension and Steering (50 scored questions, 75 minutes)

  • A. Steering System (12)
  • B. Suspension, Frame, and 5th Wheel (16)
  • C. Wheel Alignment (13), including camber, caster, kingpin inclination (KPI), toe, and axle alignment
  • D. Wheels, Tires, and Hub (9)

Study tip: Know how each alignment angle affects tire wear patterns. Many alignment questions start with a worn tire.

T6: Electrical/Electronic Systems (50 scored questions, 90 minutes)

  • A. General Electrical/Electronic System Diagnosis (14): voltage drops, opens, shorts, and grounds
  • B. Battery and Starting System (11); C. Charging System (7)
  • D. Lighting Systems (6); E. Related Vehicle Systems (12), such as gauges, body controls, and data networks

T7: Heating, Ventilation, and Air Conditioning (40 scored questions, 60 minutes)

  • A. HVAC Systems Diagnosis, Service, and Repair (6)
  • B. A/C System and Component Diagnosis, Service, and Repair (20)
  • C. Heating and Engine Cooling Systems (6)
  • D. Operating Systems and Related Controls (8)

What questions look like: Expect to read high- and low-side gauge readings and decide whether they point to an overcharge, a restriction, a weak compressor, or moisture in the system.

T8: Preventive Maintenance Inspection (50 scored questions, 75 minutes)

T8 tests the inspection side of every other system, much like a thorough PM service.

  • A. Engine Systems (10)
  • B. Cab and Hood (5)
  • C. Electrical/Electronics (10)
  • D. Frame and Chassis (22): brakes, drivetrain, steering, tires and wheels, suspension, frame, and fifth wheel
  • E. Road/Operational Test (3)

How Should You Use the ASE T Series Blueprint to Build a Study Plan?

Because each test is scheduled separately, the blueprint helps you decide both what to study and which test to take first.

  1. Pick your order. Many technicians start with the system they work on most, such as T8 if you do PM inspections daily or T4 if you’re the shop’s brake specialist.
  2. Weight your time. Within each test, spend time in proportion to question counts. T4 air brakes (32 questions) and T8 frame and chassis (22) deserve far more hours than a 3-question area.
  3. Take a baseline. Answer a mixed set of practice questions before reviewing so you know where you actually stand.
  4. Map every miss to a task. Tie each missed question to a specific task statement in the study guide, then review that task in a textbook or service manual.
  5. Don’t skip small areas. A handful of misses in a 4-question area can still decide a close result.

What Official Resources Should You Use?

  • ASE Medium/Heavy Truck Tests Study Guide (2026): Content areas, question counts, full task lists, and sample questions for T1-T8.
  • ASE Certification: What You Need to Know (2026): Registration, testing options, score reports, and work experience rules.
  • ASE FAQs: Retakes, results, refunds, and recertification.

Commonly used references:

  • Heavy Duty Truck Systems 8th Edition (ISBN 978-0357934883)
  • Delmar ASE T1-T8 Medium/Heavy Duty Truck (8 Book Set) Test Prep Manuals, 5th Edition (ISBN 978-1305618725)
  • ASE Test Prep – T1-T8 Medium/Heavy Truck Service Set (ISBN 978-1934855591)

Frequently Asked Questions About the ASE T Series

What is the passing score for the ASE T Series tests?
ASE does not publish a fixed passing percentage. Your score report shows pass or fail, along with how you did in each content area.

How soon will I get my results?
Your detailed score report is emailed after you finish your exam appointment. Results can usually be viewed in myASE within 24 hours.

Can I take the tests before I have two years of experience?
Yes. You can test first, but ASE won’t issue the certificate until it reviews and approves your work experience. The T Series requires two years of hands-on experience, and relevant training can substitute for part of it.

If I fail, how soon can I retake a test?
You must wait 30 full days before you can purchase and schedule the same test again.

Do I need all eight tests?
No. Each test is its own certification. Master Medium-Heavy Truck Technician status requires T2 through T8.

How long does ASE certification last?
Five years. After that, you take a recertification test, which is roughly half the length of the original.

Can I test any time of year?
Testing is offered year-round, with short breaks between ASE’s quarterly registration windows. Once you buy a test, you have 90 days to schedule and take it.

Start Preparing for the ASE T Series With Pocket Prep

Whichever test you tackle first, Pocket Prep’s ASE T Series practice questions can help you prepare in short sessions that fit around shop hours. You’ll get 400 practice questions organized by T1-T8 subject, each with a detailed explanation. Use Build Your Own Quiz to focus on the test you’ve scheduled and Missed Questions to close gaps.

With a consistent study plan, you can walk into every ASE T Series test with confidence.