Diesel mechanic courses in Australia: Cert III, costs and where to study

Two Cert IIIs: pick the one that matches the gear you want to work on

The heavy diesel trade splits into two national qualifications, and both are current on training.gov.au as at September 2026. Certificate III in Heavy Commercial Vehicle Mechanical Technology (AUR31120) is the truck one: prime movers, rigid trucks, buses and trailers, mostly in dealerships, transport company workshops and roadside service. Certificate III in Mobile Plant Technology (AUR31220) is the earthmoving and mining one: excavators, dozers, loaders, graders, dump trucks and other off road plant.

If you want to end up on a mine site or in civil construction, Mobile Plant (AUR31220) is usually the code the big employers put their apprentices through. If you want trucks and road transport, it is Heavy Commercial Vehicle (AUR31120). Both are around 36 units, run as a 3 to 4 year apprenticeship, and are competency based, so you can finish early if you get signed off on everything sooner. Both codes replaced older 2016 versions (AUR31116 and AUR31216), so if a provider is still advertising the old code, ask why.

What you will actually learn

Two quals sit behind this trade and both are 36 units of competency. AUR31120 (Heavy Commercial Vehicle Mechanical Technology) is the truck and bus stream, with 22 core units and 14 electives. AUR31220 (Mobile Plant Technology) is the earthmoving stream, with 9 core units and 27 electives, so it flexes to suit whatever gear your employer runs: excavators, dozers, loaders, cranes. They share the same diesel, electrical and hydraulic backbone. Here is what you actually do with your hands.

• •Start with the non-negotiables: safe working practices around machines that weigh 20 tonnes plus, using and maintaining workshop tools and lifting gear, and working clean around diesel, oil and grease.
• •Learn servicing schedules properly: full services by hours or kilometres off the OEM schedule, oil and filters, coolant, greasing the driveline, and working through a service sheet so a truck or digger leaves the workshop with nothing missed.
• •Get deep into diesel engines: inspect and service diesel fuel injection systems, then diagnose and repair big compression ignition engines, turbos and forced induction, cooling systems and emission controls like DPFs and AdBlue.
• •Master air brakes in the truck stream: diagnose and repair heavy vehicle air braking systems, from the compressor and tanks through valves and slack adjusters, because on a 60 tonne road train the brakes are everything. Plant apprentices cover the braking systems on their machines instead.
• •Work on hydraulics in both streams: inspect and service hydraulic systems as core, and in mobile plant go further into diagnosing pumps, rams and valve banks, the systems that make an excavator dig.
• •Cover the whole powertrain: clutches, manual and automatic transmissions, drive shafts, diffs and final drives on trucks, and powershift transmissions and final drives that put power to tracks on plant.
• •Sort steering and suspension on heavy gear: diagnose and repair truck steering and airbag suspension so a fully loaded rig steers straight and rides right.
• •Build real electrical skills on 24 volt systems: test, charge and replace batteries, jump-start dead vehicles, repair basic circuits, then diagnose charging, starting and electronic control systems.
• •Learn diagnostics the modern way: units like AURTTA118 (develop and carry out diagnostic test strategies) teach you to plug the OEM laptop into a truck or machine, read fault codes and live data, and chase electronic faults instead of guessing.
• •In the plant stream, do undercarriage and tracks: inspect, service and repair track type drive and support systems, rollers, idlers, sprockets and track tension on dozers and excavators.
• •Round it out with electives that suit your workshop: welding, air conditioning, wheels and tyres, and on newer gear the electronic management systems that tie engine and transmission together.

Year by year: how the training usually runs

Every employer and RTO runs this differently, and heavy diesel more than most: some apprentices do day release at a local TAFE, plenty do week-long blocks and travel to campus, and big dealers like Komatsu run their own training academies. It is all competency based too, so you finish when you can prove the skills, not when the calendar says so, and quick learners can compress it. Treat this as the typical shape of a four year apprenticeship, not a promise.

• •First year: trade school covers safety, tools and equipment, batteries and basic electrical circuits, cooling systems and servicing operations. In the workshop you are the service apprentice: oil and filter changes, greasing, wheel and tyre work, fuel filters, and handing tools to the tradies on bigger jobs while you learn how a workshop actually runs. By the end of the year you are knocking out scheduled services on trucks or machines with someone checking your work.
• •Second year: TAFE moves into brakes (air brakes for the truck stream, machine braking systems for plant), steering and suspension, hydraulics and diesel fuel injection servicing. On the job you get trusted with real component work: brake relines, hoses and rams, suspension parts, water pumps and clutch jobs. You start carrying service jobs from start to finish and your training profile or logbook fills up as tasks get signed off.
• •Third year: this is the diagnostics year. Trade school covers engine repair and engine management, emission systems, transmissions and building proper diagnostic test strategies, and plant apprentices get into undercarriage and hydraulic diagnosis. At work you are on the laptop chasing fault codes, in on engine rebuilds and driveline jobs, and starting to ride along on breakdown and field service calls. At many RTOs this is your last year of classes.
• •Fourth year: usually little or no time at trade school, just full time on the tools while the last units get signed off in the workplace. You work at near tradesperson level, take field service calls with less and less backup, and mentor the new first year. When your employer and RTO agree you are competent you get your Certificate III and trade papers, and in some states, like NSW, heavy vehicle mechanics then apply for a motor vehicle tradesperson's certificate to do repair work unsupervised.

The farm gear variant, and the pre-apprenticeship option

There is a third branch worth knowing about: Certificate III in Agricultural Mechanical Technology (AUR30420), also current on training.gov.au. That is the one for tractors, headers, spraying and seeding gear, usually through machinery dealers in regional towns. If you grew up around farm machinery it can be the easiest door into the diesel world, and the skills cross over.

Before any of them, a pre-apprenticeship helps. Certificate II in Automotive Servicing Technology (AUR20520) runs at TAFEs around the country, including a heavy vehicle servicing stream at WA TAFEs, and Certificate II in Automotive Vocational Preparation (AUR20720) is a similar entry course. Neither is compulsory, but a Cert II plus a clean driver's licence puts you well ahead of the pack when dealers pick their apprentice intake.

How you actually enrol

You do not enrol like a uni student. You get hired as an apprentice first, then the training follows the job. Your employer signs you up through an Apprentice Connect Australia provider (the free government contracted service, find one at apprenticeships.gov.au), a training contract gets registered with your state training authority, and you and the employer pick the RTO together. The RTO is usually the local TAFE, but dealers often use their own or an industry RTO.

Still at school? Heavy vehicle and agricultural mechanical quals are available as school based apprenticeships in most states, so you can start part time in Year 11 or 12 and roll into full time when you finish.

Dealer, OEM and mining apprenticeships: the prized tickets

In this trade, the equipment makers and their dealers run some of the best apprenticeships in the country. Caterpillar dealers WesTrac (WA, NSW and ACT) and Hastings Deering (QLD and NT) take on big apprentice intakes each year, mostly through the Mobile Plant qualification, with factory level training on Cat gear. Komatsu runs its own national apprenticeship program, and Cummins takes apprentices in its engine workshops around the country. These programs are competitive, applications usually open months before the intake starts, so check their careers pages early and apply to more than one.

The big miners hire diesel maintenance apprentices directly too. BHP takes apprentices including through its FutureFit Academy training centres, and Rio Tinto runs apprentice intakes across its WA and QLD operations. Mining apprenticeships often mean FIFO or residential site rosters, higher pay than a suburban workshop, and a near guaranteed job at the end. The trade off is you live where the work is.

What the course costs, state by state (as at September 2026)

Fees change every year and depend on your age, the exact qualification and where you enrol, so always check the state's live page before you count on a number.

• •NSW: apprenticeships funded under Smart and Skilled are fee-free for apprentices commencing before 30 June 2027, so you pay no course fee. Without fee-free, the student fee was up to $2,000 for the whole apprenticeship.
• •VIC: apprenticeship training is subsidised under Skills First but it is not part of Free TAFE, so providers set their own student fees per hour of training. Expect a yearly fee in the hundreds, and check the exact figure with the TAFE via the Victorian Skills Gateway.
• •QLD: Free Apprenticeships for Under 25s pays the training costs for apprentices in priority qualifications who commence by 30 June 2027. If you are not eligible, TAFE Queensland's co-contribution fee is around $1.60 per nominal hour of training. Check your qualification is on the priority list.
• •WA: heavy vehicle and plant quals sit under Lower Fees, Local Skills. In 2026, annual course fees are capped at $400 for people under 25 or with a concession, and $1,200 for others, plus resource fees.
• •SA: qualifications on the Subsidised Traineeship and Apprenticeship List are government funded, with the course fee paid to the provider. You may still pay materials and service charges. Check the course on My Training (Skills SA).
• •TAS: apprentice training at TasTAFE is government subsidised, but note the national Fee-Free TAFE program excludes apprentices in Tasmania. Check TasTAFE's fees and payment guide for current apprentice charges.
• •ACT: apprenticeships are subsidised through the User Choice program via Skills Canberra, with a student contribution fee on top. CIT publishes the apprentice fee on each course page.
• •NT: User Choice funding subsidises apprentice training through Charles Darwin University, with a tuition contribution from you, and some eligible students get free places under NT Free Training. Check the NT Government training pages.

Who actually pays the fees

Plenty of employers, especially the dealers and miners, pay the TAFE fees for you as part of the deal. Ask before you sign the training contract.

Even where they do not offer, the award may force the issue. Under many awards, including the Vehicle Repair, Services and Retail Award that covers most diesel workshops, the employer has to reimburse your training fees and textbook costs for each year you make satisfactory progress, unless they paid the RTO up front. Check your award and entitlements at fairwork.gov.au, and for pay rates use the Fair Work pay calculator at https://calculate.fairwork.gov.au/ rather than trusting numbers on random websites.

Where you can study

Every state's main public TAFE runs at least one of the diesel quals: TAFE NSW, the Victorian TAFEs (Kangan Institute, Bendigo TAFE and GOTAFE all run Mobile Plant), TAFE Queensland, South Metropolitan and South Regional TAFE in WA, TAFE SA, TasTAFE, CIT in Canberra and Charles Darwin University in the NT.

Industry RTOs matter in this trade too. The Motor Trades Association RTOs, like MTA Institute in Queensland, deliver AUR31120 and AUR30420 with trainers who come to the workshop, and the big dealers run registered training operations of their own.

To see every provider of a code, search the code (AUR31120, AUR31220 or AUR30420) on training.gov.au and open the list of RTOs approved to deliver it, then filter by your state.

Doing it without an apprenticeship

Full fee, classroom only delivery of these Cert IIIs barely exists for locals, and where it does you would pay many thousands of dollars for a qualification employers will still question, because this trade is judged on workshop hours, not paper. The apprenticeship is the route: you get paid, your fees are subsidised or free, and you leave with 3 to 4 years of real spanner time on the exact gear employers run.

The one sensible non-apprenticeship spend is a pre-apprenticeship Cert II, which is short, often subsidised or fee-free for eligible students, and makes you a better bet at interview.

Costs beyond the course fee

Budget for the gear, not just the fees. A starter tool kit for heavy diesel runs well into the thousands over the apprenticeship, though dealers and miners often supply or subsidise tools, another reason those programs are prized. Add steel cap boots, workwear and safety glasses if your employer does not supply them, plus textbooks and any TAFE resource fees.

Help exists: eligible apprentices can get Australian Apprenticeship Support Loans paid in instalments while training (check apprenticeships.gov.au for current rates and any other support you qualify for), some states run travel and accommodation subsidies for apprentices who train away from home, and tools you buy for work are generally tax deductible, so keep every receipt.