TSB: Hydrogen fuel cell powered vehicles like the Mirai use a special high-insulation coolant designed to prevent high voltage ground faults and associated MIL ?ON? (Malfunction Indicator Light) condition. This special coolant and special water mix MUST be used any time coolant is added to the fuel cell (FC) cooling system reservoir or when major services performed on the fuel cell stack and/or fuel cell cooling system. Use of water or any coolant other than ?Toyota Genuine FC Stack Coolant? could result in damage to the fuel cell stack and/or cooling system.
