12 ATS-resume checks Diesel Mechanics need to pass in 2026, the keywords recruiters scan for, and three role-specific resume bullets to copy.
Fleet operators (Penske, Ryder, Schneider, Werner, UPS, FedEx Freight), dealer service departments (Peterbilt, Kenworth, Freightliner, Volvo, Mack), and municipal fleets all evaluate diesel tech applications either through Workday/iCIMS-driven ATS or directly with a service manager who reads for specific cert and engine OEM experience. ASE Master Truck (T1-T8) and DOT inspector certification are the credentials that get filtered for.
Engine-specific experience is the other major triage signal. "Diesel mechanic" is too generic; "Cummins ISX, Detroit DD15, Cat C15, PACCAR MX" tied to roles tells the service manager which lines you can walk into on day one. CDL Class A is a requirement at fleet shops that road-test their own repairs and a strong differentiator everywhere else.
The 12-point ATS checklist for Diesel Mechanics
ASE Master Truck cert with T1-T8 listedWrite "ASE Master Medium/Heavy Truck — T1 Gasoline Engines, T2 Diesel Engines, T3 Drive Train, T4 Brakes, T5 Suspension/Steering, T6 Electrical, T7 HVAC, T8 PMI." List each test passed with expiration. ASE acronyms are direct ATS matches.
DOT/FMCSA inspector certificationList "FMCSA-qualified brake inspector (49 CFR 396.25)," "DOT Annual Inspector," and any state-specific inspector cards. Fleets running PMI programs filter for this explicitly.
Engine OEM experience per roleName Cummins (ISX, X15, ISB, ISL), Detroit (DD13, DD15, DD16), Cat (C13, C15, 3406), PACCAR (MX-11, MX-13), Volvo (D11, D13, D16), Mack (MP7, MP8). Engine OEM is the top recruiter triage word.
Transmission and drivetrain breadthEaton Fuller manual, Eaton Endurant automated, Allison automatic (1000-4000 series), Volvo I-Shift, Mack mDRIVE, Detroit DT12. List units serviced per OEM — transmission specialists are paid premiums.
CDL Class A status (or N/A)List "CDL Class A, NC, exp 06/2027" with endorsements (H, N, T) if applicable. Fleet shops that road-test repairs require it; mention if you can pull doubles or hazmat.
Diagnostic software named per OEMCummins Insite, Detroit Diagnostic Link (DDDL), Cat ET, PACCAR Davie4, Volvo Tech Tool (PTT), Bendix ACom, Wabco Toolbox, JPRO. Diagnostic software is a hard ATS keyword.
Aftertreatment and emissions workDPF regen and cleaning, DEF/SCR, EGR system service, NOx sensor R&R, DOC service. Post-2010 emissions diagnostics is what separates senior techs from journeymen.
Brake system experience by typeAir-disc (Bendix, Meritor EX+), S-cam drum, ABS (Wabco, Bendix), automatic slack adjusters. Brake-qualified inspectors are paid more and reqs filter for them by name.
PM intervals and shop systems usedA/B/C PM intervals, fleet maintenance software (TMT Fleet Maintenance, Dossier, Fleetio, RTA, Mitchell 1 TruckSeries). Naming the shop system signals zero onboarding time.
Specialty endorsements: HVAC 609, welding, hydraulicsEPA Section 609 (MVAC) for AC work, AWS certification for structural welds, hydraulics experience for refuse/utility, lift gate. Specialty endorsements expand reqs you match.
OSHA 10/30 and hazmat trainingOSHA 10 or 30-hour General Industry, hazmat handling, lockout-tagout, hot work. Large fleets and unionized shops filter on safety credentials.
Fleet size and shop type context"180-truck OTR carrier," "45-bay dealer service department," "municipal fleet of 220 mixed Class 7/8." Service managers triage on fleet context — solo independent shop ≠ enterprise OEM dealer.
Role-specific keywords ATS scans for
These terms recur across current 2026 Diesel Mechanic job descriptions on Indeed, LinkedIn, and Greenhouse. Weave the genuine ones (those you have actually used) into your experience bullets — keywords in narrative context outrank keyword dumps in a Skills section.
Fix:List Cummins, Detroit, Cat, PACCAR, Volvo, Mack with model series per role — service managers triage on engine lineage first.
✗ ASE certs listed as "ASE certified"
Fix:Spell out T1-T8 explicitly with passed-test list and expiration; ATS does literal match on T-series acronyms.
✗ DOT inspector cert missing
Fix:Add FMCSA brake inspector / annual DOT inspector — fleets running PMI programs hard-filter on it.
✗ No diagnostic software named
Fix:Add Cummins Insite, DDDL, Cat ET, PACCAR Davie4, JPRO — service departments filter on tool familiarity.
✗ CDL absent on a road-test required req
Fix:Add CDL Class A with endorsements; if not held, note "CDL permit, scheduled road test [date]."
✗ Hours/year or trucks/year vague
Fix:Add throughput per role — PMs/week, engine rebuilds/year, fleet size supported — for hard productivity evidence.
Three example resume bullets for a Diesel Mechanic
Patterns a strong Diesel Mechanic bullet should hit: action verb at the start, role-specific noun in the middle, measurable number at the end. Adapt these to your real work; do not copy verbatim.
Performed 18-22 A/B PM services per week on 180-truck Cummins X15 fleet at OTR carrier, including DPF regen verification, brake stroke measurement, and JPRO fault-code clearing, logged in TMT Fleet Maintenance
Rebuilt 14 Detroit DD15 cylinder packs in 12-month period at Freightliner dealer, including in-frame overhauls with DDDL parameter resets and post-repair road test under CDL Class A
Led aftertreatment diagnostics for 65-unit refuse fleet, resolved chronic NOx sensor and DEF-quality codes via Cummins Insite and Cat ET, reduced regen-related downtime by 41% over 6 months
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Yes — Master Medium/Heavy Truck is T2-T8 (and T1 if gasoline applicable), recertified every 5 years. Listing partial ASE (e.g., T2, T4, T6) is still valuable and ATS matches each acronym, but "Master" status only applies once you've passed the full series. Don't claim Master without it.
Does CDL Class A really matter for shop mechanics?
Fleet shops that road-test repairs and any mobile/dispatched repair work require it. Dealer service can sometimes use a porter to move trucks, but having Class A makes you more deployable, opens road-test work, and is a 5-10% pay differential at most large fleets. Worth getting.
Should I list every engine I've touched or just primary?
List engines you can diagnose and major-repair unsupervised. "Touched once" engines should be omitted — service managers ask interview questions on listed engines, and gaps damage credibility more than a shorter list. Hierarchy: OEMs you can run a job ticket on, then OEMs you've assisted on.
Are independent shop hours valued the same as dealer hours?
Generally yes for fundamental skill, but OEM dealers value documented OEM training (Cummins QuickServe University, Detroit Diesel Training, Cat Service Training Institute). If you have factory training certificates, list them — they signal warranty-work readiness that independent experience alone doesn't prove.
Do recruiters care about EPA 609 for diesel work?
Yes if the role includes truck HVAC repair — Section 609 (MVAC) certification is federally required to purchase R-134a/R-1234yf and to service AC systems. Big fleets and dealers triage for it because AC repairs are constant in summer. Add it as a one-liner under Certifications.
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