Don't Let Your Technicians Get Fried

The need for high-voltage safety training.

Maintenance needs for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs) and all-electric vehicles (EVs) are similar to those of conventional vehicles. However, hybrid/electric vehicles have high-voltage electrical systems that range from 100V to 600V. Consequently, servicing them requires some particular precautions.

Before attempting to perform service operations on any hybrid/electric vehicle, technicians should be fully trained in high-voltage service work, advise subject matter experts (SMEs) at CDX Automotive ( “Once they are trained, the most important rule technicians need to remember is this: Never work on a high-voltage vehicle without first notifying someone who is trained in dealing with high-voltage electrocution,” they say. “There needs to be a responsible person in the work environment to check on technicians as they work around high voltage.”

The SMEs also stress that technicians need to always read the manufacturer’s service information for the vehicle they are about to service. The service information will instruct them in how to properly follow all safety procedures.

CDX Automotive, a division of Jones & Barlett Learning, is the world’s leading provider of interactive and experiential automotive curriculum for light vehicle, medium and heavy truck and bus technician training. Jones & Bartlett Learning ( is a world-leading provider of instructional, assessment and learning-performance management solutions for the secondary, post-secondary and professional markets.


The matter of servicing electric vehicles safely is to be taken seriously since high voltage can easily and quickly kill you. If you have any doubts, just think of the purpose of an electric chair. That should help everyone keep a safe mindset.

While there are many safety features built into hybrid/electric vehicles to help reduce the possibility of accidental shock, shops that decide to venture into servicing high-voltage vehicles should be prepared to spend some money on safety equipment, the SMEs say. This is no time to pinch pennies.

Some of the standard equipment for servicing high-voltage vehicle systems includes:

  • OEM or equivalent scan tools.
  • A high-quality (three-phase CAT III or CAT IV) digital volt-ohmmeter (DVOM) with appropriate high-voltage leads.
  • Insulated gloves rated for 5,000V and certified to 1,000V (Class 0), as well as approved glove covers. The gloves need to be visually inspected and air tested for any possible defects (for example, cuts, holes, tears, embedded objects, changes in texture, etc.) before each day’s use and whenever there is a reason to believe they may have been damaged.
  • Safety cones and safety tape to mark off service areas, and other such items.
  • A retrieval hook in case someone becomes disabled from electrical shock.

If you decide to service hybrid/electric vehicles, get the proper training on the high-voltage areas, as well as a full understanding of how they operate, recommend the SMEs. Make sure technicians stay alert and continually practice situational awareness.


Besides the high-voltage dangers of a hybrid/electric vehicle, there are other precautions that technicians need to be aware of. Because all hybrid/electric vehicles are designed to operate uniquely, there are safety precautions specific to each vehicle model.

One of the first safety precautions is that the vehicle should be completely powered down before working on it. The reason being: the internal combustion engine (ICE) can start at any time the vehicle’s powertrain control module (PCM) deems necessary.

Never assume that the vehicle is turned off because it is silent or still, CDX Automotive SMEs stress. The vehicle may appear to be turned off because the ICE has been shut down and the vehicle is silent, but the system can still be in “ready” mode (most vehicle models show this on the vehicle dash display panel), capable of engaging the ICE or the drive motor at any moment.

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