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Diesel Mechanics Curriculum Details

Penn Foster Career School can help you take the first step toward preparing for entry-level diesel mechanic jobs. The program is designed to help students prepare to sit for the Medium-Heavy Truck Certification Test upon completion of the program. Students can expect to learn about repairing diesel engines, brake systems, shop safety practices, and more.

Program Goal and Outcomes

Program Goal

The Diesel Mechanics/Heavy Truck Maintenance Career Diploma program provides students with knowledge of skills ranging from basic diesel engine operations to computerized truck management systems. Students will learn how to maintain and do repairs on their own trucks, work for a truck fleet or dealership, or start a full- or part-time business.

Upon completion of the program, students will be able to...
  • Recognize the role of a diesel repair technician and the many exciting career opportunities available to skilled technicians
  • Know the common tools and shop safety procedures used in the repair of heavy-duty vehicles
  • Understand the basic operation of a diesel engine and its major components
  • Describe the operation of the cooling and lubrication systems of a typical diesel engine
  • Identify the various procedures used in the inspection and rebuilding of a typical diesel engine
  • Understand the operation of a mechanical fuel injection system, the fuel-delivery system, as well as the properties of the various types of diesel fuels
  • Know the basics of computers and the specifics of the electronic operation of vehicle and engine control systems
  • Be aware of the basic theory and repair of the various electrical systems, including the battery, charging system, starting system, and lighting systems
  • Know the basic operation and repair of heavy-duty truck steering and suspension systems, along with service and repair of vehicle wheels and tires
  • Understand the operation of hydraulic and pneumatic braking devices and control systems, the interpretation of fault-indication messages, and the troubleshooting of brake system problems
  • Describe the operation and repair procedures for common heavy-duty truck manual transmissions and clutch systems
  • Identify the principles of operation, troubleshooting steps, and repair procedures for the most common types of automatic transmissions used in today’s heavy-duty trucks
  • Identify the function and operation of driveline components, troubleshooting procedures, and the tasks required for servicing driveline problems
  • Recognize the function and operation of heating, ventilation, and air conditioning systems used on heavy-duty trucks

Orientation to Diesel Mechanics/Heavy Truck Maintenance

Course 1: Orientation to Diesel Mechanics/Heavy Truck Maintenance

In this course, you’ll learn how to succeed as a Penn Foster student. You’ll also learn about the growing diesel-engine powered vehicle repair field and the increasing need for professional technicians. You’ll discover the many exciting career opportunities that are available to skilled technicians. Finally, you’ll learn about the basic operation of engines and other vehicle systems.

Lesson 1 - Starting Your Program


  • Understand how to use your Student Portal.
  • Access the Penn Foster Community and use it to find answers.
  • Connect with Penn Foster on various social media sites.
Lesson 2 - Introduction to Diesel Truck Mechanics


  • Name and describe the eight basic operating systems in a vehicle
  • Describe the basic operation of a four-cycle diesel internal-combustion engine
  • Define the terms horsepower, displacement, and compression ratio
  • Discuss the employment possibilities that are available in the heavy-duty vehicle repair field
  • List and discuss the steps needed to attain certification in the heavy-duty vehicle servicing field
Additional Course Material

Textbook: Diesel Technology

Truck Maintenance Fundamentals, 1

Course 2: Truck Maintenance Fundamentals, 1

This course includes an introduction to diesel engine operation, including how the diesel cycle differs from other types of engine cycles, and how (and why) the diesel engine has been a very popular choice for powering such a wide range of vehicles. The course also introduces several major diesel engine components and moves on to cover shop safety and tools.

Lesson 3 - Introduction to Truck Engine Operation


  • Name key developments in the history of the diesel engine
  • Describe the difference between gasoline- and dieselpowered engines
  • Explain how the engine powertrain components work together, including the cylinder block, cylinder liners, pistons, rings, rods, and crankshafts
  • Understand the differences between the diesel engine classifications by characteristics such as four-stroke, two-stroke, cylinder number, and combustion chamber design
  • Understand basic power terminology and how to make common engine calculations such as bore, stroke, horsepower, and torque
Lesson 4 - Safe Shop Practices


  • Explain and describe personal safety precautions and how to follow proper shop safety guidelines
  • Understand the safety rules needed when working with fuel injectors
  • Describe the three basic types of fires and how to properly extinguish them
  • List right-to-know laws and explain how to handle hazardous wastes
  • Describe the proper usage for a variety of tools, including torch wrenches, micrometers, precision gauges, power tools, and others
  • Identify and state the purpose of precision measuring devices and various fuel-injection system tools
  • Recognize the difference between U.S. customary and metric fasteners

Truck Engines, Part 1

Course 3: Truck Engines, Part 1

This course continues with diesel engine components. The information is divided into two lessons; each lesson includes assignments that cover a specific area of diesel-engine technology.

Lesson 5 - Diesel Engine Fundamentals, Part 1


  • Explain how to remove a vehicle’s engine
  • Identify the features of a cylinder block and cylinder liner
  • Describe the crankshaft and its purpose, including terminology and classifications
  • Understand the purpose of the flywheel and vibration damper
  • Explain the functions of the piston, piston rings, and connecting rod
  • Describe the proper installation of a piston assembly into a cylinder block
Lesson 6 - Diesel Engine Fundamentals, Part 2


  • Identify all parts that make up the cylinder head assembly
  • Describe how to disassemble the cylinder head
  • Explain common problems with cylinder heads, along with how to properly inspect and service their components
  • Describe how to install and remove a camshaft
  • Understand the purpose of each valve train component and how they’re assembled

Truck Engines, Part 2

Course 4: Truck Engines, Part 2

This course continues your study of diesel engine systems. You'll look at lubrication, cooling, air intake, and exhaust systems. The information is divided into two lessons; each lesson includes assignments that cover a specific area of diesel-engine technology.

Lesson 7 - Truck Engine Lubrication and Cooling Systems


  • Describe the components of a lubrication system in a diesel engine and understand terminology related to lubrication systems
  • Explain how to properly maintain oil filters as well as how to recognize low oil situations and name the different oil pressure indication systems
  • Select the appropriate oil for a diesel engine based on the American Petroleum Institute (API) classifications
  • Identify cooling-system components and explain their functions in diesel engines
  • Describe the difference between air and liquid cooling systems
  • Discuss the management of diesel engine cooling systems
Lesson 8 - Truck Engine Air Intake and Exhaust Systems


  • Describe both intake and exhaust system components and their purpose in diesel engines
  • Define terms such as supercharging, scavenging, and other important concepts to the intake process
  • Explain the concept of back pressure and how to route exhaust pipes to prevent harmful effects on diesel engines
  • Explain the function of roots blowers, turbochargers, the intake manifold, exhaust manifold, and charge-air heat exchangers as they relate to engine breathing
  • Describe the process of troubleshooting different components of the exhaust system
  • Understand the function of an exhaust pyrometer and other common equipment in controlling engine emissions

Fuel Systems

Course 5: Fuel Systems

In this course, you'll continue your study of diesel technology by looking at fuel and injection systems. The information is divided into three lessons; each lesson includes assignments that cover a specific area of diesel-engine or truck-system technology.

Lesson 9 - Introduction to Fuel Systems


  • Define terminology common to diesel fuels and describe diesel fuel characteristics
  • Explain the diesel fuel grades according to the standards of the American Society of Testing Materials (ASTM)
  • Understand the purpose of fuel additives along with the reasoning behind alternative fuels
  • Discuss proper fuel storage and the different factors that can lead to leakage or the presence of foreign materials
  • Explain the purpose of the fuel system’s major components
  • Identify the three types of fuel gauges and explain how they operate
  • Describe the three types of fuel lines and how they’re properly replaced
Lesson 10 - Diesel Engine Injection Systems, Part 1


  • List the five types of fuel injection systems and identify their major components
  • Define terms related to fuel injection systems including timing, injection, rate control, and others
  • Locate and describe the function of the nozzles, governors, and other essential components
  • Explain the process for removing and installing nozzle holders and nozzles
  • Outline the procedures for analyzing and diagnosing fuel injection system problems
  • Describe the function and components of an inline fuel injection pump
  • Explain how to service an inline fuel injection pump including bleeding air from the lines, and performing diagnostic tests and timing procedures
Lesson 11 - Diesel Engine Injection Systems, Part 2


  • Describe the operating principles and components of a distributor injection pump
  • Explain how to remove and install the major components of a distributor injection pump
  • Understand how mechanical unit fuel injector systems deliver fuel to the engine’s cylinders
  • Describe how to service the major components of the unit injector fuel injection systems

Truck Electronics and Engine Controls

Truck Electronics and Engine Controls

This course covers the basics of electricity and then moves on to diesel engine electrical systems, including the charging and starting systems. You'll also learn about electronic engine controls. The information is divided into two lessons; each lesson includes assignments that cover a specific area of diesel-engine or truck-system technology.

Lesson 12 - Electricity and Diesel Engine Electrical Systems


  • Explain Ohm’s law and other electrical concepts as they relate to a vehicle’s charging system
  • Describe the operation of batteries and the vehicle’s other major electrical components, including how to test and service them
  • Explain the function of the charging system and its components, including how alternators and generators work to provide power
  • Understand how to maintain a vehicle’s charging system, including how to remove and install an alternator
  • List the major components of the electrical starting system and describe their operation
  • Explain how to perform starter system tests and no-loading testing
  • Describe the operation of different starting systems, including air-powered starting systems, hydraulic starting systems, and cold-weather starting aids
Lesson 13 - Electronic Engine Controls


  • Describe the functions of the major components found in an electronic engine control system including the computer, sensors, and actuators
  • Explain the basic operation of engine control computers and identify their major components
  • Understand how engine control computers, personal computers, digital service equipment, and vehicle computer systems all interface through the vehicle’s communication system
  • Explain the operating principles of high-pressure common-rail fuel injection systems
  • List the basic steps used when troubleshooting electronically controlled diesel engines

Truck Maintenance Fundamentals, Part 2

Course 7: Truck Maintenance Fundamentals, Part 2

This course provides an introduction to the trucking industry and details key career and certification information. You'll also review safety practices and take another look at tools and measuring equipment. This course includes one lesson.

Lesson 14 - Introduction to Truck Maintenance


  • Understand truck classifications and identify common truck manufacturers
  • Discuss today’s over-the-road trucking industry and the contemporary truck technicians’ qualifications and responsibilities, including ASE certifications
  • Discuss workplace hazards and personal and procedural safety precautions that minimize their danger
  • Understand how to comply with the standards of the Occupational Safety and Health Administration (OSHA), including knowledge of hazardous materials, Material Safety Data Sheets, and other necessary information
  • Describe how to use common hand, precision measuring, and shop tools associated with diesel engine work
  • Identify Society of Automotive Engineers (SAE) fastener grades and torques
  • Read micrometers and other precision equipment
  • Make conversions between English and metric units of measurement
Additional Course Material

Textbook: Truck and Trailer Systems

Truck Electrical Systems

Course 8: Truck Electrical Systems

This course takes another look at basic electrical topics before moving on to cover truck electrical systems, such as starting and charging systems and lighting and wiring. You’ll also study truck computer systems. The information is divided into three lessons; each lesson includes assignments that cover a specific area of truck-system technology.

Lesson 15 - Truck Electrical Systems, Part 1


  • Define electrical and electronic principles as they apply to a vehicle’s circuits
  • Describe how to make series and parallel circuit hookups to construct a circuit
  • Understand magnetism and its usage in diesel engines
  • Explain how to test electric motors, solenoids, and relays
  • List the actions required to properly inspect, clean, service, and test battery systems
  • Identify the three primary battery types and the different types of terminal connections used in heavy-duty trucks
  • Explain how a battery’s elements function to produce electrical power
Lesson 16 - Truck Electrical Systems, Part 2


  • Perform voltage-drop tests and other tests on starter systems, charging systems, and lighting systems
  • Explain the principles governing the operation of electric motors and generators
  • Identify the major charging-system components and their functions
  • Describe how to clean, inspect, repair, and reassemble a starter motor
  • Explain the function of an alternator and its different components
  • Understand the effect of wire size on electrical circuits and describe the procedures followed when repairing damaged wiring
  • Interpret wiring diagrams
Lesson 17 - Truck Computer Systems


  • Describe vehicle computer system components and operation, including sensors and switches
  • Explain how to test computer systems including sensors and switches
  • Explain how to test solenoids, relays, and electric motors
  • Identify typical computer malfunctions and the meaning of dash indicator lights
  • Explain how to use scanning tools and EOM diagnostic software to service computer systems

Truck HVAC Systems

Course 9: Truck HVAC Systems

This part of your program looks at truck heating, ventilation, and air-conditioning (HVAC) systems and auxiliary power units (APUs). This course includes one lesson, which includes assignments that cover a specific area of truck-system technology.

Lesson 18 - HVAC Systems


  • List the AC components and the different types of AC refrigerants and oils
  • Explain how to diagnose, service, and repair AC components
  • Understand the operation of the cabin heating system
  • Describe how air flows through the heater and the AC systems
  • List the types of APUs and the service each type provides
  • Describe the installation and maintenance of APUs

Tires, Suspension, and Steering

Course 10: Tires, Suspension, and Steering

This part of your program deals with some of the systems and components that will most likely demand the bulk of your repair efforts. Tires and suspension systems, for example, wear out during much shorter intervals than parts such as engines. You'll also cover wheels, frames, and steering and trailer systems. The information is divided into two lessons; each lesson includes assignments that cover a specific area of truck-system technology.

Lesson 19 - Tires, Wheels, and Trailer Maintenance


  • Understand how tires and wheels are fastened to a vehicle
  • Describe the process for servicing tire and wheel systems, including inspections, repair, and replacement of faulty equipment
  • Explain the purpose and capabilities of wheel bearings
  • Describe the different types of wheel-bearing adjustments
  • Explain the differences between types of wheel seals and how to replace these parts
  • Recognize the characteristics and uses for various types of fifth wheels
  • Describe the proper procedures for coupling and uncoupling fifth wheels
  • Understand how trailer systems work and how to properly service potential problems in these systems
Lesson 20 - Suspension and Steering Systems


  • Describe the construction of a truck frame and how to perform frame inspections
  • List the types of frame defects and procedures for identifying and correcting them
  • Explain the features and operating principles of leaf and air-spring suspensions, including how to properly service, repair, and replace their components
  • Understand how a steering linkage operates and the functions of its various components, including the steering column, steering gear, input shaft, and other essential parts
  • Service and diagnose problems with the kingpin and steer axle
  • Understand steering gear and power steering system operation
  • Describe the process to follow and equipment required when aligning a truck


Course 11: Brakes

This part of your program focuses on truck brake systems, an important topic for just about any heavy-duty truck technician. You'll study different types of brake systems, their components, and how they work. The information is divided into two lessons; each lesson includes assignments that cover a specific area of truck-system technology.

Lesson 21 - Truck Brake Systems, Part 1


  • Explain the hydraulic principles that allow a brake system to work
  • Describe how to service and diagnose hydraulic brake system components, including the selection of proper brake fluids
  • Understand the operation of power brake boosters, including how to diagnose and service their components
  • Explain the operation of basic air brake systems, including air brake chambers, S-cam brakes, and slack adjusters
  • Describe how to service and diagnose both S-cam and air disc brake systems
Lesson 22 - Truck Brake Systems, Part 2


  • Explain the air system theory of operation and how it relates to the supply air system components and operation
  • List the primary and secondary air system components and their operation, including how to test and service these two systems
  • Describe the operation of the emergency/parking air system and how to service these systems according to DOT guidelines
  • Describe the differences between various types of air brake mechanical/foundation brake systems
  • Identify ABS components while explaining how to test and diagnosis ABS systems
  • Explain how to perform ABS and HABS computer system diagnosis, as well as component testing with a digital voltohmmeter

Drivelines and Transmissions

Course 12: Drivelines and Transmissions

This part of your program covers the driveline system, clutches, and drive axles before moving on to truck manual and automatic transmissions. You'll learn about the major components, operation, and general procedures for servicing these systems. The information is divided into three lessons; each lesson includes assignments that cover a specific area of truck-system technology.

Lesson 23 - Drivelines, Clutches, and Axles


  • Identify each driveline component and explain its function
  • Describe basic driveshaft test and service procedures
  • Define the terminology associated with the clutch and its components
  • Outline general procedures for testing, adjusting, and servicing clutches
  • List the drive-axle components and their operation
  • Explain how to repair, replace, service, and overhaul the drive axle
  • Describe procedures for testing, servicing, overhauling and diagnosing problems with inter-axle differentials
Lesson 24 - Manual Transmissions


  • Describe how a manual transmission and its components operate
  • List the major components in five- and six-speed manual transmissions
  • Describe maintenance, diagnosis, service, and overhaul procedures for manual transmissions
  • Explain how to service, repair, and test twincountershaft transmissions including both the main and auxiliary-transmission systems
  • Describe the operation of and service procedures for an automated manual transmission
  • Perform service and diagnostic tasks on automated transmission systems including component and computer-based testing
Lesson 25 - Automatic Transmissions


  • Understand the operation of the automatic transmission and its associated terminology
  • Explain the operation of automatic transmission components including planetary gear sets, the hydraulic valve, and torque-converter
  • Describe the general service procedures for automatic transmission components
  • Explain how to inspect and diagnose problems with Allison automatic transmissions
  • Describe the process to follow when removing and installing Allison 1000/2000/2400 series automatic transmissions

Troubleshooting and Repair

Course 13: Troubleshooting and Repair

You’ll study preventative maintenance inspections (PMIs) on over-the-road vehicles and diesel engines. Proper maintenance inspections allow you to catch problems before they become bigger, more expensive ones. This course discusses the type of maintenance programs you’ll encounter as a diesel technician, and the types of routine inspections you’ll be expected to carry out. You’ll also study DOT inspection requirements and the characteristics of an effective preventative maintenance (PM) program.

Lesson 26 - Review of Diesel Engine Topics


  • Define terms related to diesel engine operating characteristics, including horsepower and pressure ratio
  • Explain the operating principles of a two- and four-cycle diesel engine
  • Understand the ratings applied to various grades of diesel fuel
  • Identify the likely causes of general engine malfunctions, including irregular starting characteristics and engine oil leaks
Lesson 27 - Troubleshooting and Repair


  • Discuss the troubleshooting and servicing of diesel engine fuel-injection systems
  • Identify the basic components of an electronic management system
  • Recognize the fault codes used in and analyze the results of the most common EMS systems
  • Apply troubleshooting methods to diagnose cylinder head and valve problems
  • Troubleshoot lubrication system problems in a typical diesel engine
  • Identify the troubleshooting procedures related to diesel engine air cleaning systems and turbochargers
Lesson 28 - Review of Electrical, Starting, and Cooling Systems


  • Define basic electrical terms and principles such as Ohm’s law
  • Describe the operation of the most common electrical components, such as relays, fuses, switches, and semiconductor devices
  • Explain the procedures used to test and recondition diesel starters and alternators
  • Identify the basic components and properties of vehicle batteries and describe how they’re tested
  • Identify the components of a diesel engine cooling system and describe their function
Lesson 29 - PM, Inspection, and Troubleshooting


  • Interpret maintenance programs, including maintenance schedules and types of inspections
  • Explain how to perform DOT inspections and list DOT out-of-service criteria
  • Describe the importance of preventative maintenance programs and accurate maintenance records
  • List the tests and checks for modern oil analysis and the instructions for performing these tests
  • Explain how to perform a range of troubleshooting tests with attention paid to troubleshooting charts and service information
  • Prepare diesel engines for long-term and short-term storage
Additional Course Material

Textbook: Diesel Engine Troubleshooting and Repair

Additional Details

Licensing and/or certification requirements for jobs in this field are not the same in every state and may include educational, testing, and/or experiential requirements beyond those offered in the Penn Foster Program. Prospective students should contact the state professional licensing board or similar regulatory body in the state(s) where they plan to work to determine their requirements before enrolling in this Program. Click here for contact information for state licensing/regulatory boards and certain industry licensing information.
Penn Foster Career School is not approved or regulated as a school by the Maryland Higher Education Commission.

Penn Foster Career School Accreditation & Licensing Details

Penn Foster has been accredited for over 50 years. Penn Foster Career School has been thoroughly reviewed and has earned several important accreditations, certifications, and licensing. Most importantly, Penn Foster Career School is both regionally and nationally accredited.

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Sample Diesel Mechanic Lesson

Penn Foster courses are written in a way that is easy to understand, and materials are broken down into manageable lessons. Take a look at what a Diesel Mechanics/Heavy Truck Maintenance course would look like:
Penn Foster Diesel Mechanic Sample Lesson
Computer Specifications
As you know this is an online academic program. This means you will need high-speed internet access to begin your program. In addition, you will need access to a Microsoft® Windows® based computer running Windows 7® or later or an Apple® Mac® computer running OS X® or later, and an email account to participate in and complete your program.
We reserve the right to change program content and materials when it becomes necessary.
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