Run engine diagnostics on a laptop
Plug in a diagnostic computer, read stored fault codes, then follow that engine's troubleshooting steps to the cause.
Career profile
Diesel Mechanic
Bus and truck mechanics diagnose and repair engine, brake and electrical problems on heavy vehicles.
Curious why machines stop working right? Take a truck that has lost power: you hook up test gear, find the cause and repair what failed.
A day in the life
Inspect brakes for wear
Listen for leaking air and measure lining thickness to see which brake parts need repair or replacement.
Catch problems before they show up
At a planned service, change oil and filters, grease the fittings and look for worn or loose parts.
Rebuild a worn engine
Some jobs include teardowns, where you swap worn bearings or pistons and measure clearances against factory specs.
Confirm the fix, close the job
First confirm the original complaint is gone, then record the repair in the shop's electronic work-order system.
Quick facts
High school + workplace training
United States · 2025
$61,770/year
United States · May 2025
3.6% projected growth
United States · 2025–2035
Quick orientation
Preparation, pay & outlook
Preparation
High school + workplace trainingExpect substantial learning on the job.
Pay
$61,770/yearNational median, equivalent to $29.70/hour.
Outlook
3.6% projected growthAbout 24,400 openings annually, including replacement needs.
Fit, tradeoffs & changing tools
You might like this if…
- You like working through clues when the first explanation does not fit.
- You enjoy using tools and checking measurements carefully.
- You can stay thorough during familiar, repeated inspections.
Things to weigh
- Heavy parts, awkward positions, grease, and shop noise can make a shift physically tiring.
- Some shops need evening or weekend coverage; some mechanics work more than 40 hours a week.
Where AI may help
Engine software can display fault information and guide troubleshooting. On Cummins engines, it can also bring up wiring and sensor-location diagrams.
What people still lead
You inspect the actual parts, interpret measurements, and carry out the repair.
What we can’t predict yet
As fleets add electric vehicles, the amount of diesel-engine work may shrink. How quickly your shop's vehicle mix changes remains uncertain.
Pay in context
Earnings
The national median is $61,770 a year, or $29.70 an hour. Half earn more and half earn less.
The national spread
The lowest-paid 10% earned below $44,530; the highest-paid 10% earned above $88,740. These are wage percentiles, not starting and senior salaries.
Workplace affects the comparison
Annual medians were $71,460 in local government, excluding education and hospitals; $60,330 in automotive repair and maintenance; and $59,820 in truck transportation.
Openings include replacing workers
Employment is projected to grow 3.6%. The estimated 24,400 annual openings also include people changing occupations or leaving the workforce.
Getting started
Learn in an entry-level shop job
- What the route involves
- Train with experienced mechanics, starting with fluid checks, lubrication, tires, and basic repairs.
- What it can lead to
- Build toward a preventive-maintenance technician role with responsibility for inspections and routine repairs.
Complete a diesel program
- What the route involves
- Combine classroom study with hands-on work in engines, electrical systems, and diagnosis. Look for a heavy-truck focus.
- What it can lead to
- Earn a certificate or degree and meet the postsecondary preparation some employers prefer.
Most employers require high school completion. Some also require industry certification; test-driving large vehicles may require a commercial driver's license.
After entry
Career paths
This starts where the entry routes leave off: early work, growing capability, and advancement or specialization.
Get dependable at routine service
Build accuracy in inspections, lubrication, brake work, and tire repairs.
Take on harder faults
Develop electrical troubleshooting skills and tackle steering, suspension, and driveline repairs with greater independence.
Become an advanced technician
Build toward major engine and transmission rebuilds. Experienced mechanics may also mentor newer technicians.
Where you can work
Truck and bus repair shops
Work in a fixed shop with jacks, hoists, and repair bays. Some shops operate around the clock, so your shift may extend beyond daytime hours.
- Indoors
- Shift work
- Physical demands
- Safety-sensitive
Mobile fleet service
Travel in a service vehicle to work on customers' trucks. Some roles combine repairs with arranging visits and discussing estimates directly with the customer.
- Field work
- Travel
- Vehicle
- Physical demands
- Safety-sensitive
Try it
See whether the job clicks before you commit to the path.
Find a manufacturer's truck-engine troubleshooting diagram. Pick one symptom and sketch how different test results would change your next check. Notice whether tracing the cause makes you want to keep going.
Stay safe: Keep this a paper exercise; do not run tests on a vehicle.
Sources
- O*NET OnLine. 49-3031.00 — Bus and Truck Mechanics and Diesel Engine Specialists. Accessed 2026-10-02.
- U.S. Bureau of Labor Statistics. Occupational projections and worker characteristics, 2025–35. Accessed 2026-10-02.
- U.S. Bureau of Labor Statistics. Diesel Service Technicians and Mechanics. Accessed 2026-10-02.
- Cummins. QuickServe Online — INSITE. Accessed 2026-10-02.
- Ryder. Ryder Careers — Diesel Technician Roles. Accessed 2026-10-02.
- Ryder. Diesel Technician Mobile — Atlanta, Georgia. Accessed 2026-10-02.
- Texas State Technical College. Diesel Equipment. Accessed 2026-10-02.