| Key Takeaways STVT’s 13-month Diesel Heavy Truck Technician program, available at the San Antonio and Arlington campuses, is built to prepare you for the ASE Medium/Heavy Truck T-Series exams. The curriculum also includes EPA 609 prep as part of the electrical and A/C coursework, a supplementary credential that expands what a shop can assign you. New terms start every five weeks. Financial aid is available for those who qualify. |
Most people looking at diesel tech school focus on the program length and the cost. The smarter question is what the program actually prepares you to do, specifically, which certification exams you’ll be ready to pursue and how the coursework gets you there.
That’s the question the Diesel Heavy Truck Technician program at STVT is built to answer. The program covers diesel certification prep across two credential tracks: the EPA 609 A/C Technician exam, which students can sit for during the program, and the ASE Medium/Heavy Truck T-Series exams, which graduates should be prepared to pursue after entering the field. Both are available at STVT’s San Antonio and Arlington campuses. The diploma is 60 credit hours completed in 13 months, with rolling enrollment every five weeks.
What Certifications Does STVT’s Diesel Program Prepare You For?
| Capsule: STVT’s diesel training is built around ASE T-Series preparation. EPA 609 certification is also covered as part of the electrical and A/C coursework. |
ASE certification is the certification employers in the diesel field use to evaluate technicians. The ASE Medium/Heavy Truck T-Series covers the systems a diesel tech regularly works on, engines, drivetrains, brakes, electrical systems, emissions, and suspension. STVT’s curriculum is structured to build the knowledge and hands-on experience of those exams.
EPA 609 is a separate, narrower certification. Section 609 of the Clean Air Act requires certification for any technician who services motor vehicle air conditioning systems, including the cab A/C on heavy trucks. It’s not the primary focus of diesel repair, but it’s a real part of the job when a truck comes in with a climate control problem. STVT’s curriculum includes EPA 609 prep within the Basic Electrical and Fundamentals of Heating, Ventilation, and A/C course. The course covers refrigerant types, recovery and recycling procedures, and the proper use of MVAC servicing equipment– content which is assessed on the exam. Students who complete that coursework should be prepared to sit for the exam before they graduate.
ASE works on a longer timeline. The National Institute for Automotive Service Excellence requires at least 2 years of documented field experience before a technician can achieve full certification, or 1 year combined with a 2-year degree. STVT builds the technical foundation, the system knowledge, and diagnostic thinking that makes those exams achievable once you’re in the field.
*STVT does not guarantee a third-party license. License requirements for taking and passing license examinations are not controlled by STVT but by outside agencies and are subject to change by the agencies without notice to STVT. Therefore, STVT cannot guarantee that graduates will be eligible to take license examinations, regardless of their eligibility status upon enrollment.
What the EPA 609 Covers and Where It Fits in Diesel Work
| The EPA 609 certification is a federal requirement under Section 609 of the Clean Air Act. You cannot legally service a motor vehicle air conditioning system without it. |
The EPA 609 is not a diesel-specific certification. It’s a federally required certification for any technician who services motor vehicle air conditioning systems, and it applies to diesel techs because heavy truck cabs have A/C.
When a truck comes in needing repair, and the driver reports the A/C isn’t cooling, the tech who handles that repair needs EPA 609 certification to legally recover and recharge the refrigerant. Without it, a shop can’t legally assign that work to that tech. It’s a test with 25 open-book questions, 84% passing score required.
The exam covers refrigerant types, recovery and recycling procedures, proper use of MVAC servicing equipment, and the Clean Air Act regulations behind those requirements. Once earned, it doesn’t expire.
What the ASE T-Series Exams Test
The ASE T-Series is eight exams covering medium and heavy trucks, Class 4 through Class 8. Each exam covers a specific system. Passing all eight earns Master Medium-Heavy Truck Technician status.
| ASE Exam | Subject | Systems Covered |
| T1 | Gasoline Engines | Gas engine systems in medium/heavy trucks |
| T2 | Diesel Engines | Fuel injection, emissions, turbochargers, engine controls |
| T3 | Drive Train | Clutches, transmissions, driveshafts, axles |
| T4 | Brakes | Air brakes, hydraulic brakes, ABS |
| T5 | Suspension & Steering | Front axles, steering geometry, wheel alignment |
| T6 | Electrical/Electronic Systems | Batteries, charging, starting, lighting, data systems |
| T7 | Heating, Ventilation & A/C | Cab climate control systems |
| T8 | Preventive Maintenance | PMI procedures, fluid checks, safety inspections |
T2 is the exam most directly tied to STVT’s diesel program. It tests diagnosis and repair of diesel engines, fuel systems, combustion components, cooling, lubrication, emissions controls, and electronic engine management. T6 and T7 also connect directly to what students learn in STVT’s electrical and HVAC coursework.
These exams don’t test definitions. They present diagnostic scenarios and ask what’s wrong, what caused it, and what the correct repair is. If you’re thinking about how training prepares you for them, keep that in mind.
How STVT’s Curriculum Maps to the Exams
| STVT’s diesel coursework covers electrical systems, engine overhaul, emissions, suspension, and cab HVAC, each mapping to specific EPA 609 and ASE T-Series content. |
STVT’s Diesel-Heavy Truck Technician program is structured as a hybrid of classroom instruction and hands-on lab work. Here’s where the curriculum directly connects to certification content:
Basic Electrical and Fundamentals of Hearing, Ventilation, & A/C is where students prepare for the EPA 609 exam. The course covers electrical diagnosis, battery and charging systems, lighting, and the A/C electrical components in heavy trucks. The hands-on work, recovering refrigerant, testing circuits, diagnosing A/C faults, is the applied version of what the EPA 609 exam tests in its open-book format.
Diesel Engines and Fuel Systems covers inspection, disassembly, reassembly, and returning engines to factory specs. This is the T2 exam’s core territory: fuel delivery, combustion, cooling systems, lubrication, and engine braking. Students don’t just read about these systems, they work on them in the lab.
Diesel Drivetrain and Chassis Electrical Systems teaches students how to inspect, diagnose, and repair heavy-duty mechanical drivetrains, including manual and automatic transmissions, clutches, and differentials.
Brakes, Suspension, and Steering covers the systems tested on T4 and T5, with hands-on diagnosis and repair of air brakes, hydraulic systems, steering geometry, and suspension components.
Each course builds knowledge that can show up on an exam, and builds the hands-on pattern recognition that helps exam questions click when you’ve actually done the work.
Why the Lab Hours Help You Learn Diesel-Heavy Truck Repair Better
| Reading about how a diesel particulate filter regenerates is different from watching one fail during a diagnostic exercise and figuring out why. |
ASE exam questions are written to reflect real shop scenarios. They describe symptoms, list what a technician found during diagnosis, and ask what the correct next step is. A technician who has run through those scenarios in a lab, who has seen the difference between a healthy and a failing system, answers those questions differently than someone who prepared only with a study guide.
Leroy Chavez, Jr. is a Diesel Instructor at STVT San Antonio. According to Chavez, lab days where the students participate in engine disassembly are particularly powerful. “That’s when everything starts to click,” he explains. “Students gain an understanding by seeing how components work together and by physically engaging with the engine. The hands-on experiences bring the concepts to life.”
STVT’s program puts students on industry-standard equipment at both campuses. The labs are a core part of the curriculum. We believe that hands-on training is the best way to prepare students for future certification.
What to Expect After Graduating from STVT’s Diesel Heavy Truck Technician Program
Graduates of STVT’s Diesel Heavy Truck Technician program should be prepared to pursue entry-level jobs as diesel mechanics, diesel technicians, oil change technicians, and A/C technicians. Some graduates also pursue Original Equipment Manufacturer (OEM) Training Certification, which manufacturer-aligned dealerships and fleet service centers look for specifically.
“What many people do not realize is how broad the diesel industry is,” Chavez points out. “Diesel technology is used in large semis, yachts, cruise ships, locomotives, oilfields, and even medium and light-duty vehicles.”
STVT’s Career Services team works with students before and after graduation. The STVT team helps with resume development, interview preparation, and job search guidance. Employment is not guaranteed, but a structured job search with support is a different experience than going it alone.
The two-year field experience requirement for full ASE certification means graduation is the start of the credential journey, not the end.
Come See STVT’s Diesel/Heavy Truck repair Lab
If you want to see what the labs and program look like in person, schedule a tour at the San Antonio or Arlington campus. Or call 866-480-9766 to talk with an Admissions representative about starting dates and next steps.
Frequently Asked Questions
Does STVT guarantee I’ll pass the ASE or EPA 609 exams?
No. STVT does not guarantee third-party certifications. Passing scores and eligibility requirements are controlled by ASE and the EPA, not STVT, and are subject to change by those agencies. The program prepares you to pursue these credentials. Passing them is your responsibility.
*STVT does not guarantee a third-party license. License requirements for taking and passing license examinations are not controlled by STVT but by outside agencies and are subject to change by the agencies without notice to STVT. Therefore, STVT cannot guarantee that graduates will be eligible to take license examinations, regardless of their eligibility status upon enrollment.
Can I sit for the EPA 609 exam before finishing the 13-month program?
Yes. Students typically sit for the exam, which is administered by an external party, during the Basic Electrical and Fundamentals of Heating, Ventilation, and A/C course. Students who pass the exam will already have earned that certification before completing the program.
How many years of field experience does ASE require before I can earn full certification?
ASE requires a minimum of two years of documented hands-on work experience, or one year combined with a two-year degree in automotive repair. STVT’s program satisfies the training requirement. The field experience has to come from working in the industry after graduation.
What’s the difference between the ASE T-Series and the A-Series?
The A-Series covers passenger cars and light-duty vehicles. The T-Series covers Class 4 through Class 8 medium and heavy trucks. If your goal is to work on commercial trucks and heavy equipment, T-Series is the relevant track. T2 (Diesel Engines) is the exam most directly tied to STVT’s diesel program curriculum.
If I have prior mechanical experience, do I still need to complete the full program?
Transfer and proficiency credits are determined by STVT’s admissions staff on a case-by-case basis, as outlined in the school catalog. Contact the San Antonio or Arlington campus to discuss your specific background before enrolling. Prior experience is worth mentioning; it’s part of the conversation, not a guarantee of reduced requirements.
Disclaimer: Information within this blog is for general information purposes only. STVT does not assume or guarantee certification/licensures, specific job/career positions, income earning potential, or salary expectations based on the programs offered at STVT. STVT does not guarantee third-party certifications. Certification requirements for taking and passing certification examinations are not controlled by STVT but by outside agencies and are subject to change by those agencies without notice to STVT.