Repairer Driven News
« Back « PREV Article  |  NEXT Article »

Toyota offers best practices for safely repairing EVs

By on
Repair Operations | Technology
Share This:

Toyota has produced a list of recommended procedures technicians need to be aware of when working any of its vehicles that contains a high-voltage battery.

The best practices, spelled out in an article recently published on the Toyota Genuine Parts website, apply to any electric vehicle (EV), plug-in hybrid electric vehicle (PHEV), fuel cell electric vehicle (FCEV) , or hybrid vehicle (HV) produced by Toyota.

Repairers looking to estimate, diagnose or repair one of these vehicles are directed to Toyota’s Technical Information System (TIS) website,, for “the assets that will help you get up-to-speed on these high-tech vehicles,” the article says. “In many cases, Toyota has a repair bulletin that outlines how to protect yourself during repairs and provides precautions that need to be taken before the inspection and service of the high-voltage circuit.”

Among particular interest, Toyota said, are procedures related to safely disarming the high voltage systems, and the additional refinishing time these vehicles may require.

Always remember that safety comes first, no matter which type of vehicle or battery is being worked on. “Always do your research and take the appropriate precautions before working on one of these sophisticated vehicles,” Toyota advises.

Best practices

Any time a vehicle with a high-voltage battery has been in a collision, there’s a chance that the battery and its contents have been compromised, raising dangers of fire and electrocution. Toyota recommends that, after a crash, all high-voltage batteries be treated as though they are unstable, as a precaution.

What follows is the OEM’s list of recommendations:

  • After turning the car off and removing the service plug grip, wait at least 10 minutes to discharge the high-voltage capacitor inside the inverter.
  • If the battery has been damaged or punctured, isolate the vehicle at least 50 feet away from other flammable or combustible materials.
  • Objects that could start the engine or hybrid system, including key fobs, should be stored away from the vehicle and locked in a container out of range from the vehicle.
  • Once a high-voltage battery is disabled and discharged, the vehicle should never be rolled on its wheels, as this can generate voltage to the battery system.
  • High-voltage personal protection equipment, including gloves (rubber and leather), boots, face shield, and safety glasses, are necessary.
  • Check insulated gloves to ensure they are free of cracks, tears, and other types of damage before starting your work.
  • Never carry any metal objects — like mechanical pencils or rulers — near the vehicle you are servicing; if they are accidentally dropped into the engine, they can cause a short circuit.
  • Before touching a bare high-voltage terminal, wear insulated gloves and use a tester to make sure that the terminal voltage is 0V.
  • After disconnecting or exposing a high-voltage connector or terminal, insulate it immediately using insulating tape.
  • Bolts and nuts used for high-voltage terminals should be tightened to the specified torque — insufficient or excessive torque could cause a failure.
  • Post a “CAUTION: HIGH VOLTAGE DO NOT TOUCH” sign near the vehicle to notify others that the high-voltage system is being inspected and/or repaired.
  • When welding on an EV, PHEV, FCEV, or HV, follow the same precautions as when welding on a conventional vehicle; as a best practice, disconnect both the 12V battery and the high-voltage battery service disconnect.
  • After servicing a high-voltage system and before reinstalling the service plug grip, check that you have not left any parts or tools inside, that the high-voltage terminals are firmly tightened, and that the connectors are correctly connected.
  • When working on a high-voltage circuit, use either a tool wrapped with vinyl insulation tape or use an insulated tool.

Repairers should always read the appropriate bulletin for the vehicle they are repairing before beginning work, to check for additional guidelines and cautions.

Care of 12V auxiliary batteries

If a vehicle is to be stored for 30 days or more, Toyota recommends that the shift lever be in the “park” position, and all lights, accessories, and the hybrid system be turned off before disconnecting the negative terminal of the 12-volt auxiliary battery.

If an auxiliary battery must be recharged, Toyota recommends using a battery charger designed for the job, with microprocessors that can vary the charge rate based on the battery’s needs. This can prevent damage to the battery caused by high current rates. Special Service Tool (SST) GR8 Battery Diagnostic Station is the Toyota specified battery charger designed for charging auxiliary batteries.

For proper handling and charging of hybrid vehicle auxiliary batteries, see Toyota Technical Service Bulletin TSB-0043-16, found on TIS.

In use, the auxiliary battery is charged by the high-voltage battery. If the auxiliary battery is low on charge, you may use a jump box to “ready” the vehicle and allow the onboard charging system to restore the 12-volt battery to its ideal level.

As with internal combustion engine (ICE) vehicles, the 12-volt auxiliary battery must be disconnected before any welding is done, Toyota cautions.

“The most significant reason to disconnect a vehicle battery before the repair is to protect yourself and the vehicle’s electrical systems, especially while welding,” Toyota said.

“A 12V battery needs to be disconnected, essentially taking off-line all circuits and connected components to protect them when welding on the vehicle,” cautions Mike Anderson of Collision Advice. “In addition, the main SRS ECU (Electrical Control Unit) wire harness should be disconnected and any ECUs within 18-inches of weld locations removed. These extra steps help prevent the potential for accidental airbag discharge and damage to ECUs from induced welding current.”

Hydrogen fuel cell system

The Toyota Mirai is powered by a hydrogen fuel cell system, in which hydrogen from the fuel tank reacts chemically with air coming in from the intake grille to create electricity. The electricity powers an AC motor that drives the rear wheels.

Toyota cautions that before starting repairs on a Mirai, an FCEV-Qualified Toyota Dealership and Technician must be consulted to assess the damage to the hydrogen fuel system components: the fuel cell stack, fuel system piping, receptacle, tube joints, sensors, regulator, and tank assemblies.

The precautions for other EVs and HVs apply to the Mirai, with the added consideration of the compressed hydrogen gas stored in high-pressure tanks. The hydrogen must be released to removing the tanks from the vehicle. Toyota directs repairers to have an FCEV-Qualified Toyota Technician help with releasing the hydrogen.

Other considerations:

  • High-pressure hydrogen pipes have red insulation for identification purposes.
    Toyota genuine fuel cell stack coolant cannot be reused – refill only with new Toyota Genuine FC Stack Coolant Full Service Kit-20L (P/N 08889-80350).
  • When cutting and welding, do not allow sparks or hot fragments to contact the hydrogen fuel components. If that occurs, remove the hydrogen tanks before proceeding.
  • Do not allow solvents to contact the hydrogen fuel tanks.

The Mirai has been produced in very limited numbers. In calendar year 2021, just 2,629 were sold in the US.

I-CAR EV resources

On the I-CAR website, you will find links to other OEM-specific information, compiled by I-CAR’s Repairability Technical Support (RTS) team. You’ll also find a number of other general EV-related information, including I-CAR’s comprehensive best practice on HV disconnection, as well as technical articles written by I-CAR experts.

The documents within the best practice include:


Featured image provided by Toyota.



Share This: