What do Diesel Service Technicians and Mechanics Do

Diesel Service Technicians and Mechanics

Diesel-powered engines are more efficient and durable than their gasoline-burning counterparts. These powerful engines are standard in our Nation's trucks, locomotives, and buses and are becoming more prevalent in light vehicles, including passenger vehicles, pickups, and other work trucks.

Diesel service technicians and mechanics, including bus and truck mechanics and diesel engine specialists, repair and maintain the diesel engines that power transportation equipment. Other diesel technicians and mechanics work on other heavy vehicles and mobile equipment, including bulldozers, cranes, road graders, farm tractors, and combines. Others repair diesel-powered passenger automobiles, light trucks, or boats.

Increasingly, diesel technicians must be versatile enough to adapt to customers' needs and to new technologies. It is common for technicians to handle all kinds of repairs, working on a vehicle's electrical system one day and doing major engine repairs the next. Diesel maintenance is becoming increasingly complex, as more electronic components are used to control the operation of an engine. For example, microprocessors now regulate and manage fuel injection and engine timing, increasing the engine's efficiency. Also, new emissions standards may require mechanics to retrofit engines with emissions control systems, such as emission filters and catalysts, to comply with pollution regulations. In modern shops, diesel service technicians use hand-held or laptop computers to diagnose problems and adjust engine functions.

Technicians who work for organizations that maintain their own vehicles spend most of their time doing preventive maintenance. During a routine maintenance check, technicians follow a checklist that includes inspecting brake systems, steering mechanisms, wheel bearings, and other important parts. Following inspection, technicians repair or adjust parts that do not work properly or remove and replace parts that cannot be fixed.

Diesel service technicians use a variety of tools in their work, including power tools, such as pneumatic wrenches that remove bolts quickly; machine tools, such as lathes and grinding machines to rebuild brakes; welding and flame-cutting equipment to remove and repair exhaust systems; and jacks and hoists to lift and move large parts. Common hand tools—screwdrivers, pliers, and wrenches—are used to work on small parts and get at hard-to-reach places. Diesel service technicians and mechanics also use a variety of computerized testing equipment to pinpoint and analyze malfunctions in electrical systems and engines. Employers typically furnish expensive power tools, computerized engine analyzers, and other diagnostic equipment, but workers usually accumulate their own hand tools over time.

Work Environment

Diesel service technicians and mechanics held about 275,400 jobs in 2020. The largest employers of diesel service technicians and mechanics were as follows:

  • Truck transportation - 20%
  • Wholesale trade - 14%
  • Automotive repair and maintenance - 9%
  • Local government, excluding education and hospitals - 9%
  • Self-employed workers - 7%

Diesel technicians usually work in well-ventilated and sometimes noisy repair shops. They occasionally repair vehicles on roadsides or at worksites.

Injuries and Illnesses

Diesel service technicians and mechanics often lift heavy parts and tools, handle greasy or dirty equipment, and work in uncomfortable positions. Sprains and cuts are common among these workers. Diesel technicians need to follow some safety precautions when in the workplace.

Work Schedules

Most diesel technicians work full time. Overtime is common, as many repair shops extend their service hours during evenings and weekends. In addition, some truck and bus repair shops provide 24-hour maintenance and repair services.

Education & Training Required

High school courses in automotive repair, electronics, English, mathematics, and physics provide a strong educational background for a career as a diesel service technician or mechanic. Many mechanics have additional training after high school.

A large number of community colleges and trade and vocational schools offer programs in diesel engine repair. These programs usually last from 6 months to 2 years and may lead to a certificate of completion or an associate degree. Some offer about 30 hours per week of hands-on training with equipment; others offer more lab or classroom instruction. Formal training provides a foundation in the latest diesel technology and instruction in the service and repair of the equipment that technicians will encounter on the job. Training programs also teach technicians to interpret technical manuals and to communicate well with co-workers and customers. Increasingly, employers work closely with representatives of educational programs, providing instructors with the latest equipment, techniques, and tools and offering jobs to graduates.

Although formal training programs lead to the best prospects, some technicians and mechanics learn through on-the-job training. Unskilled beginners generally are assigned tasks such as cleaning parts, fueling and lubricating vehicles, and driving vehicles into and out of the shop. Beginners are usually promoted to trainee positions as they gain experience and as vacancies become available.

After a few months' experience, most trainees can perform routine service tasks and make minor repairs. These workers advance to increasingly difficult jobs as they improve their ability and competence. After technicians master the repair and service of diesel engines, they learn to work on related components, such as brakes, transmissions, and electrical systems. Generally, technicians with at least 3 to 4 years of on-the-job experience will qualify as journey-level diesel technicians.

Employers often send experienced technicians and mechanics to special training classes conducted by manufacturers and vendors, in which workers learn about the latest technology and repair techniques.

Other Skills Required

Employers usually look for applicants who have mechanical aptitude and strong problem-solving skills and who are at least 18 years old and in good physical condition. Technicians need a State commercial driver's license to test-drive trucks or buses on public roads. Many companies also require applicants to pass a drug test. Practical experience in automobile repair at an automotive service station, in the Armed Forces, or as a hobby is valuable as well.

How to Advance

Experienced diesel service technicians and mechanics with leadership ability may advance to shop supervisor or service manager, and some open their own repair shops. Technicians and mechanics with sales ability sometimes become sales representatives.

Although national certification is not required for employment, many diesel engine technicians and mechanics find that it increases their ability to advance. Certification by the National Institute for Automotive Service Excellence (ASE) is the recognized industry credential for diesel and other automotive service technicians and mechanics. Diesel service technicians may be certified in specific areas of truck repair, such as drivetrains, brakes, suspension and steering, electrical and electronic systems, or preventive maintenance and inspection. For certification in each area, a technician must pass one or more of the ASE-administered exams and present proof of 2 years of relevant work experience. To become what's known as a master technician, all the tests in a given series must be passed. To remain certified, technicians must be retested every 5 years.

Job Outlook

Employment of diesel service technicians and mechanics is projected to grow 8 percent from 2020 to 2030, about as fast as the average for all occupations.

About 28,100 openings for diesel service technicians and mechanics are projected each year, on average, over the decade. Many of those openings are expected to result from the need to replace workers who transfer to different occupations or exit the labor force, such as to retire.


As more freight is shipped across the country, additional diesel-powered trucks will be needed to carry freight wherever trains and pipelines are not available or economical. In addition, diesel cars and light trucks are becoming more popular, and more diesel technicians will be needed to maintain and repair these vehicles.


The median annual wage for diesel service technicians and mechanics was $48,690 in May 2021. The median wage is the wage at which half the workers in an occupation earned more than that amount and half earned less. The lowest 10 percent earned less than $35,730, and the highest 10 percent earned more than $76,150.

In May 2021, the median annual wages for diesel service technicians and mechanics in the top industries in which they worked were as follows:

  • Local government, excluding education and hospitals - $60,670
  • Wholesale trade - $55,940
  • Automotive repair and maintenance - $47,630
  • Truck transportation - $47,120

Many diesel technicians, especially those employed by truck fleet dealers and repair shops, receive a commission in addition to their base salary.

Most diesel technicians work full time. Overtime is common, as many repair shops extend their service hours during evenings and weekends. In addition, some truck and bus repair shops provide 24-hour maintenance and repair services.

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