The ASE T-series is not one exam. It is 8 tests, each a certification of its own, from gasoline engines (T1) to preventive maintenance inspection (T8). Pass T2 through T8, with the work experience behind them, and you are a Master Medium-Heavy Truck Technician; T1 stands on its own. Below: the format of each test, what each one covers, and 7 questions to try, one from every test.
During a cold-start check, the intake air heater relay clicks on, but a clamp-on ammeter shows 0 A in the heater supply cable. Which of these could be the cause?
Explanation
Incorrect: Welded relay contacts would keep the heater drawing current all the time, not show 0 A.
Incorrect: The coolant sensor input affects whether the heater is commanded, and the relay did click on.
Incorrect: A grounded element would draw very high current or blow its fuse, not read 0 A.
Correct: A clicking relay shows the control side works, so zero current in the supply cable means the power path is open, most often a burned-out grid element.
Question 2 of 7 · T3 Drive Train · 40 itemsNot answered
A drive axle makes noise only when the truck turns a corner and is quiet driving straight. Which of these could be the cause?
Explanation
Correct: Differential side and pinion gears turn against each other only when the wheels turn at different speeds, so their wear makes noise in turns and stays quiet going straight.
Incorrect: Worn wheel bearings make noise driving straight as well, and it changes when the load shifts to one side.
Incorrect: Loose pinion bearing adjustment makes a growl or whine in straight driving too, changing with load.
Incorrect: Worn ring and pinion teeth make noise driving straight as well, changing with drive or coast load.
Air leaks continuously from the exhaust port of the steer-axle quick release valve, but only while the service brakes are held applied. This could be caused by a:
Explanation
Incorrect: A ruptured chamber diaphragm leaks at the chamber itself, not out of the quick release valve exhaust.
Correct: A quick release valve exhausts through its port only when brakes are released; a leak there only while the brakes are applied means its diaphragm or seat is not sealing.
Incorrect: A restricted delivery line slows application and release; it does not cause a leak at the exhaust port.
Incorrect: A leaking foot valve inlet leaks at the foot valve exhaust with the brakes released, not at the quick release valve during an application.
Question 4 of 7 · T5 Suspension and Steering · 50 itemsNot answered
Both tires of a truck's dual assembly are worn noticeably more in the center of the tread than at the shoulders. This could be caused by:
Explanation
Correct: Overinflation makes the tread crown in the middle, so the center wears faster than the shoulders.
Incorrect: Wrong toe makes a feathered pattern across the tread, not center wear.
Incorrect: Too much negative camber wears the inner shoulder, not the center.
Incorrect: Underinflation does the opposite, wearing both shoulders more than the center.
Question 5 of 7 · T6 Electrical/Electronic Systems · 50 itemsNot answered
On an air-brake tractor, none of the tractor or trailer stop lamps work. With the brakes applied, 12 V is present at the stop-lamp switch input and 0 V at its output. The cause is:
Explanation
Correct: Air-brake tractors use a pressure-operated stop-lamp switch; with 12 V in and 0 V out while the brakes are applied, the switch is not closing.
Incorrect: An open circuit breaker would leave no voltage at the switch input, but 12 V is there.
Incorrect: An open ground at the lamps would still leave voltage at the switch output.
Incorrect: A dead short in the trailer stop circuit would trip the stop-lamp circuit protection, so the 12 V at the switch input would be gone too; here the input still has 12 V.
Question 6 of 7 · T7 Heating, Ventilation, and A/C · 40 itemsNot answered
A truck's coolant has a layer of engine oil floating in the surge tank, and the engine oil level is dropping. Which of these could be the cause?
Explanation
Incorrect: A failed pressure cap loses coolant or lowers the boiling point; it does not put oil into the coolant.
Incorrect: A heater control valve only handles coolant; it cannot add oil.
Correct: An oil cooler leak lets higher-pressure oil push into the coolant, so oil floats in the surge tank and the oil level drops.
Incorrect: A worn water pump bearing makes noise or leaks coolant at the weep hole; it does not put oil in the coolant.
During a PMI, charging voltage is low and the engine runs hot under load. The alternator and coolant pump share the same belt. Which of these could be the cause?
Explanation
Incorrect: High ground resistance lowers charging voltage but does not make the engine run hot.
Incorrect: A failed regulator affects charging only, not engine temperature.
Correct: When one belt drives both the alternator and the coolant pump, a slipping belt lowers charging output and coolant flow at the same time.
Incorrect: A thermostat stuck open makes the engine run cool, not hot.
Answer every question to see your score
Pick an answer and the explanation for every option opens. Each test has its own page with more questions and its content-area split; the practice test mixes all eight, with a filter per test.
Questions and time, test by test
Checked Oct 23, 2026 against each source linked in the table. The totals include 10 unscored research questions on each test, not marked.
Master Medium-Heavy Truck Technician takes seven tests, T2 through T8. T1 is a certification of its own and does not count toward Master. Each test is valid for 5 years, and each certification must stay current to keep Master status, so the Master title lapses when any one of the seven does.
Experience:2 years of hands-on work. You can take the tests first and finish the experience later; the certificate waits for it.
Order: T8 inspects the systems that T3, T4 and T5 teach you to repair, so it reads easier after T3, T4 and T5.
Cost: all seven in one order come to $468 as of October 2026, registration included. The catch is the 90-day window; see T-series cost.
Renewal: by recertification test only, because the Renewal App is not for T tests.
Seven, not eight. The 2026 study guide marks T2–T8 as required for Master and leaves T1 out. The same guide's introduction also says "T1-T9"; that is a typo, since every other ASE page lists T1–T8.
Looking for diesel certification?
"ASE diesel certification" can mean three different tests: T2 for medium and heavy trucks, ASE A9 (Light Vehicle Diesel Engines) or ASE L2 (Electronic Diesel Engine Diagnosis Specialist). If you work on trucks, it is T2. The diesel certification guide sorts out the other two.
Guides for every ASE test
ASE certification →Every ASE test series, the requirements and the steps from myASE to certificate
ASE study guide →Free official study guides, 2026 changes, licensed books, task-list plan
Master Technician →The eight tests A1–A8, Master truck T2–T8, and how to keep the status
ASE test cost →Registration, test, retake and recertification fees for each test, as of Oct 2026
Diesel certification →Which diesel test to take: T2 for trucks, A9 for light vehicles, L2 above them
ASE recertification →Recertification tests, remote testing and the Renewal App: when, how and what each costs
How to become a mechanic →School or on-the-job, then the ASE tests: the path from first job to certified technician
Mechanic certification →ASE certification, school certificates, OEM programs and state licenses: what each one is
ASE T-series, quick answers
How many ASE T-series tests are there?
Eight, each its own certification: Gasoline Engines (T1), Diesel Engines (T2), Drive Train (T3), Brakes (T4), Suspension and Steering (T5), Electrical/Electronic Systems (T6), Heating, Ventilation and A/C (T7) and Preventive Maintenance Inspection (T8).
Is T1 required for ASE Master truck certification?
No. Master truck takes the seven tests T2–T8, so T1 is optional: take it if you service gasoline trucks.
Can I take an ASE T test online?
Not the first time: a first attempt is test center only. Recertification can be done remotely.
What score do I need to pass a T test?
The passing score is not published. The "70%" figure that circulates online comes from ASE's entry-level student tests, not from the professional T tests. Scoring in detail.