Key Responsibilities and Required Skills for Journeyman Heavy Duty Mechanic

🎯 Role Definition

A Journeyman Heavy Duty Mechanic is an experienced technician responsible for diagnosing, repairing, and maintaining heavy equipment and commercial vehicles such as trucks, buses, trailers, construction equipment, and agricultural machinery. This role requires advanced mechanical, hydraulic, and electrical skills combined with strong safety practices, documentation discipline, and the ability to work independently or lead small teams to maximize fleet uptime and ensure regulatory compliance.

📈 Career Progression

Typical Career Path

Entry Point From:

Apprentice Heavy Duty Mechanic / Diesel Apprentice
Diesel Technician or Automotive Technician with heavy equipment experience
Vocational/technical school graduate with relevant internship or shop experience

Advancement To:

Lead Heavy Duty Mechanic / Shop Lead
Fleet Maintenance Supervisor or Foreman
Field Service Manager or Senior Diagnostic Technician
Maintenance Manager or Operations Manager

Lateral Moves:

Mobile Service Technician / Roadside Technician
Parts & Inventory Specialist for heavy equipment
Training Instructor or Technical Trainer

Core Responsibilities

Primary Functions

Diagnose complex engine, transmission, driveline, electrical, and hydraulic system problems on heavy duty diesel and gasoline powered equipment using computerized diagnostic tools, manufacturer service information, and hands-on inspection techniques.
Perform complete engine overhauls, component rebuilds, and major repairs including removal, disassembly, reconditioning, and reassembly of diesel engines, transmissions, torque converters, and differentials to factory or OEM specifications.
Troubleshoot and repair air brake systems, ABS systems, and related pneumatic components to ensure vehicle safety and compliance with DOT regulations, including leak testing and pressure diagnostics.
Inspect and repair hydraulic systems, pumps, cylinders, valves and hoses; identify contamination, cavitation or internal component failure and perform precision repairs or replacements to restore full system performance.
Diagnose and repair electrical systems and components, including alternators, starters, wiring harnesses, sensors, ECM/TCU modules, CAN bus issues, and instrument clusters using multimeters, oscilloscopes, and scan tools.
Perform scheduled and preventive maintenance (PM) services per fleet maintenance schedules—oil changes, filter replacements, lubrication, cooling system service, belt and hose inspections, battery testing and charging system checks—to maximize uptime and reduce lifecycle costs.
Conduct road tests and functional checks after repairs to validate systems performance, calibrate engines and electronic control modules, verify brake effectiveness and ensure repairs meet quality and safety standards.
Use industry-specific diagnostic software and OEM service manuals to interpret fault codes, complete diagnostic flowcharts, update firmware or calibrations, and document findings in the maintenance management system (CMMS).
Repair and align steering and suspension systems including steering boxes, tie rods, kingpins, bushings, springs, air suspension components and shock absorbers to maintain vehicle stability and ride quality.
Perform welding, fabrication and structural repairs on frames, brackets, mounts and bodywork using MIG/TIG/stick welding techniques as required to restore structural integrity and safety.
Replace and maintain cooling systems components—radiators, water pumps, thermostats, thermostatic switches, hoses and clamps—and troubleshoot overheating issues using pressure tests and infrared tools.
Maintain comprehensive service records, write accurate repair orders, provide detailed work descriptions, parts used, and time spent to support warranty claims, cost tracking and continuous improvement initiatives.
Source, recommend and install replacement parts or retrofit kits consistent with OEM standards and fleet policies, including cross-referencing parts, verifying part compatibility and ordering specialty items as necessary.
Ensure all repaired equipment adheres to federal, state and local regulatory requirements including DOT inspections, emissions controls, and workplace safety regulations; prepare vehicles for mandated inspections and assist during audits.
Mentor and provide technical guidance to junior mechanics and apprentices by demonstrating best practices, troubleshooting approaches, and safety procedures while delegating tasks and reviewing their work for quality assurance.
Respond to after-hours emergency callouts and field service requests to diagnose and correct roadside failures or breakdowns in a timely and professional manner as part of a 24/7 fleet support program.
Operate shop lifts, hoists, diagnostic rigs and heavy equipment safely; follow lockout/tagout procedures and enforce PPE use to maintain a safe work environment and minimize risk of injury.
Implement and support continuous improvement programs by identifying recurring faults, recommending design or process changes, and collaborating with procurement to reduce warranty and repair costs.
Participate in parts inventory management by reporting low-stock items, inspecting incoming parts for defects, and helping optimize stock levels to reduce machine downtime and expedite repairs.
Prepare cost estimates and time-to-complete projections for complex repairs, communicate clear scope and timelines to supervisors or customers, and obtain required approvals before proceeding with non-routine work.
Collaborate with operations, safety and logistics teams to schedule maintenance windows, coordinate vehicle availability, and support seasonal or project-based fleet demands to maintain service levels.

Secondary Functions

Maintain and update digital maintenance records in the CMMS and assist with data entry and work order closeout to ensure historical traceability and KPI reporting accuracy.
Train and support apprentices or less experienced technicians through structured feedback, technical coaching, and hands-on demonstrations to build team capability.
Assist in development of shop-level standard operating procedures (SOPs), checklists and preventive maintenance plans to improve consistency and service quality.
Participate in safety meetings, hazard assessments, and incident investigations; recommend corrective actions and track resolution to closure.
Support procurement by validating parts returns, warranty claims with suppliers or OEM representatives, and coordinating with external vendors for specialty repairs.
Contribute to special projects such as fleet electrification readiness, implementation of telematics-based preventive maintenance, or retrofitting equipment to meet new regulatory standards.
Help maintain a clean, organized and efficient shop floor by following 5S principles, disposing of hazardous waste properly, and ensuring tools and equipment are calibrated and secured.
Assist sales or customer service teams with technical consultations, repair recommendations, and quotes for out-of-scope or customer-requested work to build trust and repeat business.

Required Skills & Competencies

Hard Skills (Technical)

Advanced diesel engine diagnostics and repair (turbochargers, fuel systems, injectors, timing systems, engine management).
Proficient with heavy duty electronic diagnostics, ECM/TCU fault code interpretation, and CAN bus electrical troubleshooting.
Air brake systems expertise including S-cam, disc brake, ABS, air dryer and governor service and troubleshooting.
Hydraulic and pneumatic systems repair and troubleshooting, including pumps, valves, cylinders and filtration systems.
Experience with transmissions, clutches, differentials and driveline component repair and rebuilds for heavy equipment.
Ability to read and interpret wiring diagrams, hydraulic schematics, service manuals and OEM technical bulletins.
Skilled in welding, metal fabrication, machining and structural repair methods common to heavy equipment maintenance.
Proficiency with computerized maintenance management systems (CMMS), diagnostic software (e.g., Detroit, Cummins INSITE, Cat ET), and digital inspection tools.
Familiarity with DOT regulations, OSHA safety standards, EPA emissions requirements, and company fleet policies.
Competent in preventive maintenance planning, record keeping, parts identification, and inventory control.
Comfortable using specialty shop tools and diagnostic equipment: multimeter, oscilloscope, pressure/vacuum gauges, borescopes, and lift systems.
Experience performing road tests, end-of-line functional verification, and post-repair validation procedures.

Soft Skills

Strong problem-solving and analytical reasoning to diagnose intermittent and complex mechanical failures.
Clear verbal and written communication skills for documenting repairs, explaining issues to supervisors/customers, and collaborating with team members.
Time management and prioritization to balance scheduled maintenance, emergency repairs and project work with minimal supervision.
Attention to detail and quality orientation to ensure work is completed to specification and meets safety standards.
Teamwork and mentorship mindset to support apprentices and maintain a collaborative shop culture.
Customer-focused professionalism when interacting with fleet managers, drivers and external stakeholders.
Adaptability and continuous learning to stay current with evolving diesel technologies, electronics and emission controls.
Dependability, integrity and a safety-first attitude to uphold workplace policies and regulatory requirements.

Education & Experience

Educational Background

Minimum Education:

High school diploma or GED with relevant technical experience; vocational or trade school coursework in diesel technology preferred.

Preferred Education:

Completed apprenticeship or journeyman certification in Heavy Duty/Commercial Vehicle Mechanics.
Formal diploma or certificate in Diesel Technology, Heavy Equipment Mechanics, or equivalent technical program.
ASE, manufacturer (e.g., Cummins, Detroit, CAT) or industry certifications a strong plus.

Relevant Fields of Study:

Diesel Technology / Heavy Duty Truck Repair
Heavy Equipment Maintenance & Fabrication
Automotive Electrical Systems & Electronics

Experience Requirements

Typical Experience Range:

3–7 years of hands-on heavy duty diesel or heavy equipment mechanical experience.

Preferred:

5+ years of experience servicing a commercial fleet or in a heavy equipment repair shop with demonstrated competency in diagnostics, major component overhauls, and leadership or mentorship responsibilities.
Experience with specific OEM diagnostic tools and large-fleet maintenance programs is highly desirable.