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newSchoolWorks.com › VoTechWorks › Transportation › Diesel & Heavy Truck › Externship / Worksite Placement – Diesel & Heavy Truck › Lesson 2
TRN-DIES20-08 · Lesson 2 · 148 clock hours · field

Supervised On-Site Service Hours – Phase 1 (Weeks 1–6)

Objective. Students perform employer-assigned diesel and heavy-truck service tasks under direct journeyman supervision, logging each task against the corresponding ASE T-series area in their daily field journal.

⚠ Pending professional review

This lesson, its worked examples and its practice questions has not yet been verified by a certified examiner or master technician in the trade or by a certification or approval body. It is a study draft and may contain errors. Do not use it as instructions for work on a job site or on live equipment. Always follow your instructor, your supervising professional, and current official references and regulations.

VoTechWorks program approval and accreditation are still in progress. Credentials are issued only by the certifying bodies named in each program, after their own exams.

What Phase 1 Is and Why It Matters

Phase 1 of your externship (Weeks 1–6) is where classroom knowledge meets real shop pressure. You will perform employer-assigned diesel and heavy-truck service tasks under the direct supervision of a journeyman technician. Every job you touch, every system you inspect, and every part you replace must be recorded in your field journal and linked to the corresponding ASE T-series task area. This documentation is not paperwork for its own sake—it is the evidence that you are building the breadth of hands-on experience employers and credentialing bodies expect of a competent diesel technician.

Your Responsibilities Each Workday

Arrive on time, in proper PPE, and ready to work. Before you begin any task, confirm with your journeyman supervisor what the job entails and what hazards are present. At the end of each repair or inspection event—before you move to the next vehicle—open your journal and complete at least one entry. A complete entry includes:

Writing this entry while the job is fresh in your memory produces more accurate records. Waiting until Friday afternoon leads to vague, incomplete entries that will not satisfy the minimum standard of 30 complete entries by the end of Week 6.

Working with Your Site Supervisor

At the end of each workweek, bring your hour log to your journeyman supervisor for initials. This is not a formality—it is a professional conversation. Your supervisor will give you a brief verbal comment on your performance. Transcribe that comment word-for-word (or as close as possible) into your journal, then write one area for improvement you identified yourself. Being honest about where you need to grow shows professional maturity and helps your instructor tailor coaching during the required on-site visit.

Building Your Portfolio With Diagnostic Photos

With your employer's written or verbal permission documented in your journal, photograph at least two diagnostic findings each week. Good subjects include a worn brake lining measured against the minimum thickness spec, a corroded battery terminal, a contaminated fuel filter element, a cracked air line, or a leaking turbocharger oil seal. Each photo must be accompanied by a written annotation explaining what you found, why it matters, and how it relates to the repair decision. These annotated images become portfolio evidence for interviews and, in some cases, supplemental documentation for OEM certification programs such as Cummins or Caterpillar factory training pathways.

Safety Is Not Optional

Personal Protective Equipment (PPE): Wear the PPE required by the site at all times—at minimum, safety glasses, steel-toed boots, and hearing protection in high-noise areas. Gloves appropriate to the chemical or task must be worn when handling diesel fuel, engine oil, coolant, DEF (diesel exhaust fluid), or refrigerant-adjacent components.

Lockout/Tagout (LOTO): Before working on any system where stored energy—electrical, hydraulic, pneumatic, or mechanical spring—could cause movement or release, follow the site's LOTO procedure. Never assume a vehicle is safe because the key is out of the ignition. Air systems on heavy trucks retain pressure even after shutdown. Hydraulic cylinders on dump bodies or lift gates can drop without warning. Confirm zero energy state before you place any part of your body under a raised load.

Vehicle Movement Hazards: In a busy fleet shop, trucks move in and out constantly. Always make eye contact with drivers before walking behind or beside a vehicle. Use wheel chocks whenever a vehicle is on a grade or whenever you are working under it. Never rely on the parking brake alone as your only means of preventing rollaway.

Chemical Hazards: Diesel exhaust fluid (DEF) is mildly corrosive to some metals and irritating to skin and eyes. Engine coolant is toxic if ingested. Used engine oil and diesel fuel are potential carcinogens with prolonged skin contact. Consult the site's Safety Data Sheets (SDS) for any substance you handle.

Instructor On-Site Visit: Your instructor will visit you at least once during Phase 1 to observe your task performance and review your journal. Treat this visit as a professional evaluation—your supervisor is present, and your conduct reflects on your program and your future employer references.

Meeting the Minimum Standard

By the end of Week 6 your journal must contain:

Falling short of 30 entries does not mean you did not work hard—it usually means entries were missed in the moment and cannot be reconstructed accurately afterward. Build the journaling habit in Week 1 and it will carry you through the entire externship.

Key terms9

ASE T-series task areaOne of the subject domains within the ASE Medium/Heavy Truck technician credential (such as Gasoline/Diesel Engines, Brakes, or Electrical/Electronic Systems) used to classify specific service tasks for credentialing and journaling purposes.
Field journalA bound, carbon-copy work-order log used during the externship to document each repair or inspection event, including complaint, diagnosis, corrective action, parts, and ASE task area.
Journeyman supervisorAn experienced, credentialed diesel technician at the externship site who provides direct oversight, instruction, and performance feedback to the student throughout the placement.
Lockout/Tagout (LOTO)A OSHA-required procedure for isolating all energy sources—electrical, hydraulic, pneumatic, or mechanical—on equipment before service, preventing unexpected startup or energy release that could injure workers.
Diagnostic findingA measurable or observable condition discovered during inspection or testing that identifies the cause of a complaint or a defect requiring correction, such as a worn component or an out-of-spec measurement.
PortfolioA student-assembled collection of annotated photos, completed journal entries, and supporting documents that demonstrates competency and real-world experience to future employers and credentialing programs.
DEF (Diesel Exhaust Fluid)A urea-and-water solution injected into the exhaust stream of SCR-equipped diesel engines to reduce nitrogen oxide emissions; mildly corrosive to certain metals and an eye/skin irritant.
Weekly hour logAn employer-provided form on which the student records total hours worked each day and the site supervisor initials at week's end to verify attendance and task participation.
Safety Data Sheet (SDS)A standardized document required by OSHA's Hazard Communication Standard that provides health, safety, handling, and emergency response information for a chemical substance used in the workplace.
In class: Each workday, students record a minimum of one completed journal entry per repair or inspection event, noting vehicle unit number, complaint, diagnosis steps taken, corrective action, parts used, and the ASE T-series task area the job most closely matches. · At the end of each week, the site supervisor initials the student's weekly hour log and provides a brief verbal performance comment; students transcribe that comment into their journal and note one area for improvement. · Students photograph (with employer permission) at least two diagnostic findings per week—such as a worn brake lining, a corroded battery terminal, or a contaminated fuel filter—and annotate the image with a written explanation for their portfolio.
Materials: Field journal (bound, carbon-copy work-order log), employer weekly hour-log form, smartphone or shop camera (with employer sign-off), ASE T-series task list, PPE per site requirements, site-issued shop tools
Check: Instructor makes one on-site visit per student during Phase 1 to observe task performance and review journal entries; journal must contain a minimum of 30 complete entries with ASE task codes by end of week 6, and the site supervisor's weekly initials must be present for all six weeks.

Practice check8

Answer each question, then check it. Nothing is recorded; this is your own practice.

ASE T-series – Brakes
1. A student completes a brake inspection on Unit 47 and finds the brake lining thickness is at the minimum allowable limit. Which journal entry element confirms exactly which ASE T-series domain this job falls under?
ASE T-series – General Safety / Preventive Maintenance & Inspection
2. Before removing a hydraulic line from a dump-body lift cylinder with the bed in the raised position, what is the most critical first action?
ASE T-series – Program Requirements
3. By the end of Phase 1 (Week 6), what is the minimum number of complete journal entries with ASE task codes required?
ASE T-series – Professionalism / Program Requirements
4. A student wants to photograph a contaminated fuel filter for the portfolio. What must be obtained before taking any photo in the shop?
ASE T-series – General Safety
5. A student handles engine coolant without gloves and later notices redness on their skin. Which document at the worksite provides first-aid and handling information for that chemical?
ASE T-series – Electrical/Electronic Systems / Professionalism
6. At the end of Week 3, the journeyman supervisor tells the student, 'Your torque wrench technique is good but you need to slow down when reading scan tool data.' What should the student do with this feedback?
ASE T-series – General Safety
7. A student is working in a high-noise area where air impact wrenches are in constant use. Beyond safety glasses and steel-toed boots, which additional PPE is required?
ASE T-series – Professionalism / Program Requirements
8. Which practice best ensures that a student's journal entry is accurate and detailed enough to satisfy the Phase 1 requirement?
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