The ASE T4 Brakes test is the brakes test in ASE's Medium/Heavy Truck series. It has 50 scored questions in three content areas, plus 10 unscored questions, and you get 75 minutes for all 60. Air brakes is by far the biggest area at 32 questions (64.0%), split into air supply and service systems (15), mechanical/foundation brakes and wheel bearings (13), and parking brakes (4). Hydraulic brakes follow with 11 questions (22.0%), then ABS, automatic traction control, stability control and collision warning/avoidance with 7 (14.0%). Every question ties back to one or more tasks in ASE's published task list, so the task list is your checklist. Questions are four-option multiple choice, including Technician A / Technician B items, "which of these could be the cause" items and EXCEPT items. T4 is one of the seven tests, T2 to T8, that ASE requires for Master Medium/Heavy Truck Technician.
01The test specification
The ASE test specification for ASE T4 Brakes splits the 50 scored questions across three content areas. ASE adds 10 unscored questions for research, and you have 75 minutes for all of them. Each area links to five free questions.
| Area | Content area | Scored questions |
|---|---|---|
| A | Air Brakes Diagnosis and Repair | 32 (64%) |
| B | Hydraulic Brakes Diagnosis and Repair | 11 (22%) |
| C | Antilock Brake System (ABS), Automatic Traction Control (ATC), Electronic Stability Control System, and Collision Warning/Avoidance System Diagnosis and Repair | 7 (14%) |
| Total | 50 |
02What is the ASE T4 Brakes test?
T4 is the brakes test in ASE's Medium/Heavy Truck series, the truck tests for Class 4 through Class 8 trucks and tractors. Its task list is mostly about air brakes: the compressor and everything that dries, stores and controls the air, the foundation brakes at each wheel, hubs and wheel bearings, and spring parking brakes. It also covers hydraulic brakes on trucks, and the electronic systems built on top of the brakes: ABS, automatic traction control (ATC), electronic stability control (ESC) and collision warning/avoidance.
T4 is not the same test as A5 Brakes, the brakes test in ASE's automobile series. They are separate certifications with separate task lists, and T4 counts toward ASE's Master Medium/Heavy Truck Technician recognition, not Master Automobile Technician. If you work on cars too, the car test is covered in our A5 Brakes study guide.
The test has 50 scored questions and 10 unscored ones, 60 in all, and you get 75 minutes. Every question is multiple choice with four options, (A) to (D). ASE includes the unscored questions to gather performance statistics for future tests, and you cannot tell which ones they are, so treat every question as if it counts.
Passing is one half of certification. ASE also asks you to document relevant work experience, which for the truck series is 2 years, and its study guide says suitable vocational training may count toward it; the details are at workexp.ase.com. The study guide does not publish a passing score. Once certified, you hold the certification for 5 years, and you renew it with a shorter recertification test, which for T4 is 25 questions in 30 minutes.
ASE's truck study guide marks seven tests, T2 to T8, as required for recognition as a Master Medium/Heavy Truck Technician, and T4 is one of them. T1 Gasoline Engines is in the series but is not on that list.
03What does each content area cover?
Area A: Air Brakes Diagnosis and Repair (32 questions)
Area A is the only area ASE splits into sub-areas, each with its own question count: 15, 13 and 4, which add up to the area's 32. Between them they hold 35 tasks.
Air supply and service systems (15 questions). Twenty tasks. The first is where a truck job starts: read the driver/vehicle inspection report (DVIR), confirm the complaint on a road test, and look at the driver's account and the maintenance history. Then you diagnose stopping, leak, pull, grab and drag complaints that start on the supply or service side, and time the air build-up and measure how fast the system loses air. The supply side runs from the compressor and its drive (belts, tensioners, idlers, gear and coupling), its intake, oil and water lines, through the governor and unloader, to the reservoirs. You drain the tanks and judge what comes out, whether oil, water or debris, and service the relief, check and automatic drain valves and the air drier with its heaters and wiring. The service side covers gauges and pressure sensors, low pressure warnings, lines and couplings and their routing, the foot valve, the stop and park light switches, the trailer hand control valve, relay and quick release valves with anti-compounding, the tractor protection valve, and the spring brake control valves. The last task asks you to decide whether a fault sits on the tractor or the trailer.
Mechanical/foundation brakes and wheel bearings (13 questions). Ten tasks. You diagnose poor stopping, early wear, noise, pulling, grabbing, dragging and pedal feel complaints that come from the foundation brakes, then work through the parts at the wheel: service brake chambers with their diaphragms, return springs, pushrods and clevises; automatic slack adjusters; S-cams, rollers, bushings, camshafts, spiders and anchor pins; and air disc brake calipers. Shoes, pads, drums and rotors are inspected, measured and replaced, and you choose replacement lining with the friction rating the job calls for. Wheel ends are part of this sub-area: cleaning, lubricating and adjusting conventional bearings, one-nut and two-nut types included, with new seals and wear rings, and fitting and maintaining unitized hub assemblies to the maker's spec. ASE's spec table names this sub-area Mechanical/Foundation and Wheel Hub, while its task list heading says Wheel Bearings.
Parking brakes (4 questions). Five tasks, two of them almost identical. You test spring brake chambers and replace them, disposing of the old ones as local rules require; check the spring brake relay and control valves and their plumbing; cage and uncage the spring brakes by hand; and test the parking brake interlock with its valve, modules, switches and indicators.
Area B: Hydraulic Brakes Diagnosis and Repair (11 questions)
Twenty tasks, the most tasks per question of the three areas. Diagnosis is split two ways: complaints caused by the hydraulic system and complaints caused by the drum or disc mechanical parts, each covering poor stopping, noise, early wear, pulling, grabbing, dragging and pedal feel. The hydraulic side covers pressure testing and leak checks (with a scan tool where the system has a pressure actuator and fault codes), pedal free play, the master cylinder and bench bleeding, lines and hoses, metering, proportioning and combination valves, the pressure differential valve and its warning circuit, wheel cylinders and calipers, and testing, bleeding or flushing the fluid and picking the right type. The mechanical side covers measuring drums and rotors, shoes with their springs, hardware and adjusters, and pads. Parking brakes appear here too, both the driveline type and mechanical or electronic apply systems, along with the indicator lamp. The list ends with brake assist: diagnosing booster problems on hydraulic and hydraulic/electric assist systems, servicing the booster, and the stop light switch circuit.
Area C: Antilock Brake System (ABS), Automatic Traction Control (ATC), Electronic Stability Control System (ESC), and Collision Warning/Avoidance System Diagnosis and Repair (7 questions)
Twelve tasks. You watch ABS operation, its self-test and the warning lamps, the dash lamp for trailer ABS included, and diagnose ABS faults by blink codes or a scan tool. Complaints include poor stopping, wheel lock-up, false activation, odd pedal feel, travel or pulsation, and noise. You test and replace ABS parts, which on a truck can be air, hydraulic, electrical or mechanical. The same blink-code and scan-tool approach applies to traction control and stability control, and the sensors (wheel speed, yaw, steering angle, pedal position) are tested, calibrated and serviced to the maker's procedure. Collision warning/avoidance has two tasks of its own: diagnosing the system, and removing and installing its parts with sensor calibration and module programming. The list also covers braking faults caused by vehicle modifications, wiring and connector repair, faults that start in a related system, and clearing codes to confirm the fix.
04What kind of questions are on it?
ASE's truck study guide has nine sample questions for T4. Seven are about air brakes and two about hydraulic brakes. None is about ABS or the other electronic systems, though area C still carries 7 scored questions.
Two are Technician A / Technician B items. One is about parking brakes that will not apply, and the correct answer was neither technician; the other is about a service brake that is slow to release, and only Technician B was right. Judge each statement on its own. See how to answer Technician A / B questions.
Most of the others start from a symptom and ask which of four parts or conditions could cause it: uneven braking, a chamber that leaks on application, every wheel locking under light pedal pressure, too much water when a tank is drained, and hydraulic brakes that drag at every wheel. For these, follow the air or fluid path from the symptom back to the part that sits where the fault shows up.
EXCEPT questions
Two samples are EXCEPT items, one hydraulic (a pull to one side under braking) and one air (poor stopping power). ASE puts a line before them warning that the question contains the word EXCEPT. Three of the four options could cause the problem, and you are looking for the one that could not. The T4 samples have no question built on a pictured measurement, but the task list asks you to measure drums and rotors, time air build-up and check the air loss rate, so know what each check measures and what a bad result points to.
05Where should your study time go?
Area A is 32 of the 50 scored questions (64.0%). With hydraulic brakes, areas A and B are 43 of 50 (86.0%). Area C, the electronic systems, is 7 questions (14.0%).
Inside area A, the air supply and service sub-area alone is 15 questions (30.0% of the test), more than all of area B's 11. Foundation brakes and wheel bearings add 13 (26.0%), so those two sub-areas are 28 of 50 (56.0%). Parking brakes are 4 (8.0%).
So start with air: how it is made, dried, stored and delivered to the chambers, and what each valve does when the pedal goes down or the parking brake is set. Then foundation brakes and wheel ends. Area B has 20 tasks for 11 questions, close to two tasks per question, so cover all of it at a working level rather than going deep on a few tasks. Area C has 12 tasks for 7 questions.
Use the task list as a checklist and mark each task you could explain. ASE says every question represents one or more tasks, though not every task appears on the version of the test you see. Pace: 60 questions in 75 minutes is 1 minute 15 seconds each.
06Registering, retesting and recertifying
You register and pay through ase.com. ASE charges a $34 registration fee per order plus $62 for each test, so T4 on its own comes to $96, and each extra test in the same order adds $62. ASE sets the fees and the registration dates, so check ase.com before you book. The full breakdown is in ASE test fees and registration.
The test is delivered on screen. ASE's truck study guide points to a free demo of the testing platform at ase.com/free-test-drive, and says every ASE test has a pop-up English to Spanish glossary. More on the format: how ASE tests work.
If you do not pass, ASE makes you wait 30 days before you can take the test again. Spend the month on area A first, since it carries 32 of the 50 scored questions.
After you pass and your 2 years of work experience are documented, the certification runs for 5 years. To renew it you take the T4 recertification test, 25 questions in 30 minutes; you are eligible for it only after passing the full certification test once.
07Questions people ask
- How many questions are on the ASE T4 Brakes test?
- 60 questions in 75 minutes: 50 scored and 10 unscored. ASE uses the 10 unscored questions to gather statistics for future tests, and you cannot tell which ones they are, so answer all 60.
- How much of ASE T4 is about air brakes?
- Air Brakes Diagnosis and Repair is 32 of the 50 scored questions (64%): 15 on air supply and service systems, 13 on foundation brakes and wheel bearings, and 4 on parking brakes. Hydraulic brakes have 11 questions, and ABS, traction control, stability control and collision warning/avoidance have 7.
- Is ASE T4 the same as the A5 Brakes test?
- No. T4 is the brakes test in ASE's Medium/Heavy Truck series and is mostly air brakes; A5 is the brakes test in ASE's automobile series. T4 is one of the seven tests, T2 to T8, required for ASE Master Medium/Heavy Truck Technician, and it does not count toward Master Automobile Technician.
- What score do you need to pass ASE T4?
- ASE's truck study guide does not publish a passing score for T4. It publishes the content areas, the question counts and the task list. Check ase.com for how results are reported.
- How long does ASE T4 certification last?
- 5 years. To renew it you take the T4 recertification test, 25 questions in 30 minutes, which you can take only after passing the full T4 certification test once. Certification also needs 2 years of documented work experience.
- Is ToolboxPrep affiliated with ASE?
- ToolboxPrep is an independent study site, not affiliated with or endorsed by ASE (the National Institute for Automotive Service Excellence). Our questions are original, written from ASE’s published test specifications and task lists and other public sources. They are not actual ASE test questions and not recalled or “brain dump” questions. ASE is a trademark of its owner, and we never use the ASE logo. Standards and service information are cited, not reproduced.
08Sources
- ASE Medium/Heavy Truck Study Guide (Tests T1 to T8), 2026: the T4 test specification and sub-area counts, testing time, the T4 recertification length, the 2-year work experience requirement, the tests required for Master Medium/Heavy Truck Technician, the task list this page paraphrases, and the sample-question formats
- ASE (ase.com): the $34 registration fee per order, the $62 fee per test, the 5-year certification period and the 30-day retest wait
The content areas and question counts were checked against ASE's published study guide on October 17, 2026, and the task descriptions paraphrase its task list. ASE's study guide is the final word. If you find one of ours out of date, tell us.
Related: free practice questions · ten free T4 questions · How ASE tests work · ASE test fees and registration · ASE A5 Brakes study guide, the car and light-truck brakes test
09Practice for this test
ToolboxPrep T4 practice tests are weighted to the specification above, area by area, and every answer is explained, all four options. You can try five sample questions with no account.
Ten free questions per test, no account: free practice questions. How our questions are written and checked: how our questions are made.
ToolboxPrep is an independent study site, not affiliated with or endorsed by ASE (the National Institute for Automotive Service Excellence). Our questions are original, written from ASE’s published test specifications and task lists and other public sources. They are not actual ASE test questions and not recalled or “brain dump” questions. ASE is a trademark of its owner, and we never use the ASE logo. Standards and service information are cited, not reproduced.