- The One-Page Snapshot: Exam Facts at a Glance
- Fees, Scheduling, and Testing Rules
- Domain Weights: Where the 50 Scored Questions Live
- General Engine Diagnosis: The 28% Heavyweight
- Controls, Ignition, Fuel, and Emissions Quick Hits
- Mechanical Domains: Head, Block, Lube, and Cooling
- Question Style: Technician A/B and Diagnostic Scenarios
- Experience Credit and Becoming Certified
- Renewal Cheat Sheet: The T1R Test
- A Domain-Ordered Review Sequence
- Frequently Asked Questions
- The initial T1 exam has 60 questions (50 scored, 10 unscored research) and a 75-minute limit.
- General Engine Diagnosis is worth 28%, or 14 scored questions, making it the largest content area.
- A single-test order costs $96 total: $62 test fee plus $34 registration, before applicable sales tax.
- Certification needs a passing score plus ASE-approved experience, but you may test before meeting the experience requirement.
The One-Page Snapshot: Exam Facts at a Glance
This is the quick-reference version of everything you need to know about the ASE Gasoline Engines test (Test T1), part of the Medium-Heavy Truck certification series from the National Institute for Automotive Service Excellence. The test covers Class 4 through Class 8 trucks and tractors, and it is delivered by Prometric. Print this section, tape it above your bench, and use the deeper articles linked throughout for detail.
| Item | T1 Fact |
|---|---|
| Certifying body | ASE (National Institute for Automotive Service Excellence) |
| Official test name | Gasoline Engines (Test T1) |
| Vehicle scope | Class 4 through Class 8 trucks and tractors |
| Testing provider | Prometric (initial test taken at a test center) |
| Total questions | 60 (50 scored + 10 unidentified unscored research questions) |
| Time limit | 75 minutes |
| Format | Computer-based multiple choice, four options, one correct answer |
| Certification validity | Five years |
| Renewal test | T1R: 25 questions, 30 minutes, no added research questions |
Two details trip up first-time candidates. First, you cannot tell which 10 questions are unscored, so treat every item as if it counts. Second, ASE has not published a numeric passing score in the public sources we verified, and scores depend on correct answers to scored questions. For a deeper look at what that means for your preparation, see our breakdown of the T1 passing score and the T1 pass rate data.
Fees, Scheduling, and Testing Rules
The money and the calendar are where candidates make avoidable mistakes. Here is the full mechanical picture.
The fee math
- Test fee: $62 per test.
- Registration fee: $34 per order.
- Single-test order total: $96 before applicable sales tax.
- Recertification: the same $62 test fee and $34 order fee, but recertification test charges are capped at $186 per order ($220 including registration), before applicable sales tax.
Because the $34 registration is charged per order rather than per test, bundling multiple tests into one order is the cost-smart move if you are pursuing several credentials. Our full T1 certification cost breakdown walks through the scenarios.
Scheduling rules to memorize
- 90-day window: testing must be completed within 90 days of purchase.
- 30-full-day wait: after a Pass or Fail result, you must wait 30 full days before repurchasing and scheduling the same test.
- Breaks: you may take a break during the test, but the timer does not stop.
- Materials: scratch paper and pencils are supplied at the test center.
- Language support: an English-Spanish technical glossary is available.
- Flag and review: you can flag questions and review them before submitting.
Domain Weights: Where the 50 Scored Questions Live
The official content areas come from ASE's 2026 Medium/Heavy Truck study guide. The weights below translate directly into scored-question counts out of 50. Note that headings and task lists describe exam objectives, and an individual test form need not include every listed task.
| Domain | Weight | Approx. Scored Questions |
|---|---|---|
| 1. General Engine Diagnosis | 28% | 14 |
| 2. Cylinder Head and Valve Train Diagnosis and Repair | 8% | 4 |
| 3. Engine Block Diagnosis and Repair | 8% | 4 |
| 4. Lubrication and Cooling Systems Diagnosis and Repair | 6% | 3 |
| 5. Ignition System Diagnosis and Repair | 12% | 6 |
| 6. Fuel, Air Induction, and Exhaust Systems Diagnosis and Repair | 12% | 6 |
| 7. Emissions Control Systems Diagnosis and Repair | 10% | 5 |
| 8. Computerized Engine Controls Diagnosis and Repair | 16% | 8 |
Notice the shape: diagnosis-heavy domains (1 and 8) together account for 44% of scored items. Ignition plus fuel/air/exhaust adds another 24%. That means roughly two-thirds of the exam rewards diagnostic reasoning on running-engine problems rather than teardown-and-measure knowledge. For the full task-list treatment of each area, read our complete guide to all 8 T1 content areas.
General Engine Diagnosis: The 28% Heavyweight
Domain 1: General Engine Diagnosis (28%, 14 scored questions)
This is the broadest domain and the one that touches every other system. Expect questions that start with a customer complaint and ask you to choose the next best diagnostic step.
- Interpreting symptoms: hard starting, no-start, misfire, rough idle, loss of power, abnormal noises, excessive oil consumption, and overheating.
- Choosing the right test: compression tests, cylinder leakage tests, vacuum and manifold pressure readings, and oil pressure checks.
- Reading what the numbers imply: a low reading on one cylinder points somewhere very different than a low reading across all cylinders.
- Recognizing normal versus abnormal operating conditions before condemning a component.
- Sequencing: verifying the complaint, performing basic checks, then narrowing by system.
Because this domain is cross-system, the best preparation is practicing diagnostic logic, not memorizing isolated specs. When a question describes a symptom, ask yourself which tests separate the mechanical, fuel, ignition, and control possibilities most efficiently. The exam rewards the technician who isolates the fault with the fewest wasted steps.
Key Takeaway
With 14 of 50 scored questions, Domain 1 alone is worth more than Cylinder Head, Engine Block, and Lubrication/Cooling combined (8% + 8% + 6% = 22%). Start your review here and return to it often.
Controls, Ignition, Fuel, and Emissions Quick Hits
These four domains make up 50% of the scored exam between them, and they are the areas where modern gasoline medium/heavy-duty trucks differ most from older carbureted-era training.
Domain 8: Computerized Engine Controls Diagnosis and Repair (16%, 8 questions)
The second-largest domain. Know how the engine control system gathers input, makes decisions, and commands outputs.
- Sensor and actuator roles, and how a failed input changes engine behavior.
- Scan tool data interpretation, including recognizing implausible or conflicting readings.
- Diagnostic trouble codes: what they tell you and, just as importantly, what they do not.
- Basic circuit testing logic: power, ground, signal, and how a wiring fault can mimic a bad component.
Domain 5: Ignition System Diagnosis and Repair (12%, 6 questions)
Ignition faults produce misfires, hard starts, and power loss, so these questions often overlap with general diagnosis.
- Primary versus secondary circuit faults and how to tell them apart.
- Coil, plug, and wire condition and what failure patterns suggest.
- Timing and sensor input relationships that affect spark delivery.
Domain 6: Fuel, Air Induction, and Exhaust Systems Diagnosis and Repair (12%, 6 questions)
This domain links airflow, fuel delivery, and exhaust condition.
- Fuel pressure and delivery problems and their symptoms.
- Air induction restrictions and leaks, including unmetered air effects.
- Exhaust restrictions and what they do to power and backpressure.
Domain 7: Emissions Control Systems Diagnosis and Repair (10%, 5 questions)
Emissions components interact with engine performance, so a failure here can look like a drivability complaint.
- Purpose and operation of the major emissions control devices on gasoline engines.
- How a stuck or failed emissions component affects fuel trim, idle quality, and codes.
- Verifying system operation rather than simply replacing parts.
Several of these topics are answered more quickly if you think in terms of cause-and-effect chains: a vacuum leak changes air measurement, which changes fuel delivery, which sets a code, which may be misread as a bad sensor. Questions often test whether you can spot where in that chain the real fault sits.
Mechanical Domains: Head, Block, Lube, and Cooling
Together these three domains carry 22% of scored questions, or about 11 items. They are smaller individually, but they are also the most "measurable" content on the exam, which makes them efficient points if you prepare.
Domain 2: Cylinder Head and Valve Train Diagnosis and Repair (8%, 4 questions)
- Valve train components and the symptoms of wear, such as noise and loss of compression.
- Head gasket and head-related failures and how they show up in testing.
- Inspection and measurement concepts for head and valve train parts.
Domain 3: Engine Block Diagnosis and Repair (8%, 4 questions)
- Cylinder, piston, ring, and bearing wear indicators.
- Block inspection concepts and what measurements reveal about serviceability.
- Connecting abnormal noises and oil consumption to internal wear patterns.
Domain 4: Lubrication and Cooling Systems Diagnosis and Repair (6%, 3 questions)
- Oil pressure problems and their mechanical causes.
- Cooling system faults that cause overheating or undercooling.
- Understanding how lubrication or cooling failures can cascade into internal engine damage.
Question Style: Technician A/B and Diagnostic Scenarios
The T1 exam is four-option multiple choice with one correct answer. Within that format, expect two recurring item types.
Technician A / Technician B items
You are given two statements from two technicians and asked who is right. The four choices are typically: A only, B only, both A and B, or neither. The skill here is evaluating each statement independently. Candidates lose points by letting one plausible statement bias their view of the other. Read each claim, decide true or false on its own merits, then combine.
Diagnostic scenario items
These present a symptom, sometimes with test results, and ask for the most likely cause or the best next step. The trap is picking a technically true answer that is not the most efficient or most likely one. Always choose the option that best fits all the clues given, not just the first clue.
If you are wondering how this compares to other assessments, our article on how hard the T1 exam is covers difficulty in context, and the T1 practice test lets you rehearse the A/B and scenario formats under time pressure.
Experience Credit and Becoming Certified
Passing the test is only half of certification. ASE also requires approved work experience.
- Standard requirement: ASE approval of two years of relevant full-time Repair Technician experience, or the part-time equivalent.
- Testing first is allowed: candidates may test before meeting the experience requirement.
- Education and training substitutions: approved education or training can substitute for part of the experience, but the listed substitutions cannot be combined.
- Co-op credit: ASE's detailed experience table allows two years of credit for a completed ASE-accredited OEM-sponsored co-op, including its hands-on component.
- Vocational credit: the January 2026 candidate handbook summarizes vocational credit as up to half.
- Final authority: ASE reviews and approves all experience credit.
Because the co-op and vocational credit descriptions are worded differently across ASE documents, confirm your specific situation with ASE before assuming how much credit you will receive. Our T1 requirements guide covers eligibility step by step.
Key Takeaway
You do not have to wait for your experience to mature before taking the test. Passing early can lock in your knowledge while it is fresh, and the credential becomes active once ASE approves your experience.
Renewal Cheat Sheet: The T1R Test
ASE certifications are valid for five years, and T1 follows that cycle. Renewal is handled by a separate, shorter test.
| Renewal Detail | Fact |
|---|---|
| Test code | T1R |
| Length | 25 questions, no added research questions |
| Time limit | 30 minutes |
| Eligibility | Must have previously passed the corresponding initial certification test |
| Delivery options | Test center or Prometric ProProctor remote testing (subject to technical and secure-environment requirements) |
| Expired credentials | Previously certified candidates, including those whose credential has expired, may still renew |
| Fees | $62 test fee plus $34 order fee; recertification charges capped at $186 per order ($220 with registration), before applicable sales tax |
| ASE Renewal App | Covers A1-A9 only, so it does not apply to T1 |
A common mistake is assuming the mobile renewal app handles every ASE credential. It does not cover T1, so plan on a test center or remote proctored session. Also note that T1 is not required for Master Medium-Heavy Truck Technician status, which matters if you are deciding whether to pursue it alongside other tests in the series.
A Domain-Ordered Review Sequence
Rather than a generic schedule, order your review by exam weight and by how domains build on each other. Diagnostic reasoning first, system specifics second, mechanical measurement last.
General Engine Diagnosis (28%)
- Work through symptom-to-test logic: compression, cylinder leakage, vacuum, oil pressure.
- Practice interpreting readings, not just recalling procedures.
Computerized Engine Controls (16%)
- Review sensor and actuator roles, scan data interpretation, and code limitations.
- Practice spotting wiring faults that mimic component failures.
Ignition (12%) and Fuel, Air Induction, Exhaust (12%)
- Pair these because misfire and power-loss complaints cross both.
- Trace airflow, fuel delivery, and spark as a connected chain.
Emissions (10%) plus Mechanical Domains (22% combined)
- Cover emissions device operation and failure effects on drivability.
- Review head, block, lubrication, and cooling fundamentals.
- Finish with timed mixed practice using the free official study-guide samples and a full-length practice test.
One note on materials: ASE's listed truck practice-test products are T2, T4, T6, and T8, so there is no official ASE practice test for T1. T1 preparation can use the free official study-guide samples. That gap is why timed third-party practice matters for T1 specifically. If you are weighing the investment, see whether the T1 certification is worth it and what it can mean for your career through our T1 salary guide and T1 jobs overview.
Frequently Asked Questions
The initial exam has 60 questions, of which 50 are scored and 10 are unidentified, unscored research questions. You cannot tell which are which, so answer every question carefully. You have 75 minutes of testing time.
General Engine Diagnosis is the largest area at 28%, which equals 14 of the 50 scored questions. Computerized Engine Controls Diagnosis and Repair follows at 16%, or 8 questions. Together they account for 44% of the scored exam.
A single-test order costs $96: the $62 test fee plus a $34 registration fee, before applicable sales tax. Registration is charged per order, so combining multiple tests in one order avoids paying that fee repeatedly.
No. After a Pass or Fail result, a 30-full-day wait applies before you can repurchase and schedule the same test. Also remember that any test you purchase must be completed within 90 days.
You renew by passing T1R, a 25-question, 30-minute test. You must have previously passed the initial T1 test, and you can take it at a test center or through Prometric ProProctor remote testing. The ASE Renewal App covers only A1-A9, so it does not apply to T1.
That covers the must-know facts on one page. For deeper dives, start with the T1 certification overview and the T1 study guide, and keep this cheat sheet handy as your final-week checklist.