Sooner or later a hybrid or battery-electric truck is going to roll into your bay. It might be a refuse truck, a delivery van, a transit bus or a yard tractor. Before you work on it, you need high-voltage safety training. Not because the work is mysterious, but because the way you get hurt on these trucks is different from anything a diesel engine can do to you. A diesel will crush, burn or cut you. A high-voltage battery pack can stop your heart, and it does not need to be running to do it.
This guide explains what makes high-voltage work different, which credentials exist (including ASE's xEV program and the L3 test), what safe practice looks like in a truck shop, and how to fit this training into a diesel career without abandoning the skills you already have.
Why high-voltage work is different from diesel work
Most diesel shop hazards are visible. You can see a raised dump body, hear a leak, feel heat coming off a turbo. Electrical energy gives you none of those warnings. A high-voltage cable looks the same whether it is live or dead, and the energy stored in a traction battery does not go away when the key is off.
OSHA lists electrical energy alongside mechanical, hydraulic, pneumatic, chemical and thermal energy as hazardous energy, and its control of hazardous energy guidance names electrocution and burns among the injuries that can follow the unexpected release of stored energy during service. It also requires that authorized workers be trained to recognize the type and size of hazardous energy present and how to isolate and control it. On an electrified truck, that is the whole game.
Three things trip up experienced diesel techs:
- Habit. Years of grabbing a 12- or 24-volt connector without a thought do not transfer. On a high-voltage system, every orange cable gets treated as live until you have proven otherwise.
- Hidden energy. Battery packs, capacitors in inverters and other stored-energy components can stay hazardous after shutdown. The manufacturer's procedure tells you how to isolate them and how long to wait.
- Damage. A truck that has been in a collision, a flood or a fire may have a compromised battery or insulation. Those vehicles need an assessment before anyone works on them.
High-voltage safety training: what credentials exist
There is no single federal license for working on electric trucks. What exists is a mix of manufacturer training, school courses, private safety providers and industry credentials. In the US, the credentials diesel techs ask about most often come from ASE.
ASE xEV high-voltage safety program
ASE has launched an xEV high-voltage safety testing and certification program that, according to Tomorrow's Technician's report on the launch, covers both light-duty and medium- and heavy-duty hybrid and electric vehicles. It has two levels:
| Level | Who it is for | What it covers |
|---|---|---|
| Level One: xEV Electrical Safety Awareness | Anyone who may encounter electrified vehicles at work, including service, parts, sales and support staff | Recognizing high-voltage hazards and reducing risk; driving the vehicle, doing maintenance that does not involve the high-voltage system, and handling non-high-voltage parts |
| Level Two: xEV Technician Electrical Safety | Technicians and specialists who have high-voltage training and maintain a safe work area with the required PPE | Evaluating high-voltage battery and system condition, isolating and verifying de-energized systems, securing them against reactivation, re-energizing, general work on de-energized components, and assessing high-voltage vehicles after accidents |
The test can be taken online, and passing earns an electronic credential plus a printable certificate. ASE's own test series page links to its xEV test and xEV safety testing information, so check there for current cost and renewal details before you register.
ASE L3 Light Duty Hybrid/Electric Vehicle Specialist
ASE's L-series also includes L3, the Light Duty Hybrid/Electric Vehicle Specialist test. ASE describes it as identifying technicians who can diagnose hybrid and electric automobiles, SUVs and light-duty trucks. That focus matters if you work on heavy trucks: L3 is a diagnostic specialist test built around light-duty vehicles. It can be useful if your fleet runs electric pickups or vans, but for most medium- and heavy-truck techs the xEV safety levels are the more direct fit. ASE's L2 Electronic Diesel Engine Diagnosis Specialist test stays the advanced diesel credential. Our breakdown of which ASE certifications pay off covers the rest of the lineup.
Manufacturer and school training
Truck and bus manufacturers train dealer technicians on their own electrified platforms, and some community and technical colleges now offer heavy-duty high-voltage safety courses. Manufacturer training matters most because procedures, isolation points and tooling differ between platforms. A general safety credential tells an employer you understand the hazard. The OEM course tells them you know that specific truck.
The safe work sequence every high-voltage tech should know
Every manufacturer's procedure is different, and the procedure for the truck in front of you always wins. But most high-voltage safety training teaches the same general logic, and it lines up with the Level Two skills ASE lists: isolate, verify, secure, and only then work.
- Assess the vehicle. Look for collision, water or fire damage, warning lights or a damaged battery enclosure. A damaged truck gets a different procedure, and possibly a different person.
- Set up the area. Mark off the work zone so nobody wanders in, and have the right insulated tools and personal protective equipment on hand and inspected.
- Shut down and isolate. Follow the manufacturer's procedure to disable the high-voltage system, such as removing a service disconnect or opening the specified isolation point. Then wait the time the procedure requires for stored energy to dissipate.
- Lock it out. Secure the isolation point so the system cannot be re-energized while you work. That is the same principle as any lockout and tagout, applied to a battery.
- Verify zero energy. Use a properly rated meter, test the meter on a known source, check for voltage where the procedure says, then retest the meter. Never assume a system is dead because a disconnect is out.
- Work, then re-energize deliberately. When the job is done, reassemble, remove your lock, and restore the system following the procedure, with everyone clear.
Do not improvise PPE or tools. Insulated gloves, tools and meters for high-voltage work are rated for specific voltages and need regular inspection. Use what the manufacturer and your training specify, and do not borrow a light-duty kit for a heavy-duty pack without checking the ratings.
The diesel skills that still matter on electric trucks
A battery-electric truck does away with the diesel engine and aftertreatment, but a lot of the truck is still a truck. It still has air brakes, steering, suspension, axles, tires, cab electrics and, on vocational trucks, hydraulics and power take-offs. That is a big reason our analysis of why electric trucks will not kill diesel jobs argues that the transition changes the work rather than erasing it.
The techs who adapt best usually have three things going for them:
- Strong electrical fundamentals. If you are comfortable with Ohm's law, voltage drop testing and wiring diagrams on 12- and 24-volt systems, high-voltage training builds on that foundation.
- Comfort with software. Electric trucks lean even harder on laptops, controllers and fault codes than modern diesels do.
- Procedure discipline. Techs who already follow service information step by step have an easier time with high-voltage procedures, where skipping a step is not an option.
Checklist: are you ready to work on a high-voltage truck?
- I have completed high-voltage safety training appropriate to the work I will do, not just awareness training.
- I have manufacturer training or the manufacturer's procedure for this specific truck.
- I know where the high-voltage isolation points are and how long to wait after isolation.
- I have my own lock and know my shop's lockout and tagout procedure for high-voltage systems.
- My insulated gloves, tools and meter are rated for the job and have been inspected.
- I know how to verify absence of voltage, including testing my meter before and after.
- I know what to do, and who to call, if a truck arrives with a damaged or overheating battery.
- I know when to stop and ask instead of pushing ahead.
How to get started without leaving diesel
You do not have to choose between diesel and electric. A practical order looks like this: start with an awareness-level course so you can work safely around electrified trucks, then move to technician-level high-voltage safety training once your shop actually services them, and pick up manufacturer training on the specific platforms your fleet or dealer runs. If your work includes electric light trucks or vans, ASE L3 can add diagnostic depth later. Ask your employer to pay for it. A shop taking on electrified vehicles needs trained people, and that is a fair conversation to have.
Bottom line
High-voltage safety training is the price of admission for working on hybrid and electric trucks, and it is a reasonable one for a diesel tech to pay. Get awareness training now, step up to technician-level training such as ASE's xEV Level Two when your shop starts servicing electrified trucks, and treat the manufacturer's isolate, lock and verify procedure as non-negotiable. Keep your brake, hydraulic and electrical skills sharp, because the truck around the battery still needs a good technician.