Toyota Mirai 2017 Owner's Manual page 408

408
8-2. Steps to take in an emergency
4
The fuel cell stack coolant level
is satisfactory if it is between
the "FULL" and "LOW" lines on
the reservoir.
Fuel cell stack coolant reser-
voir
"FULL" line
"LOW" line
If the amount of fuel cell stack coolant is low:
Immediately contact your Toyota dealer.
If the amount of fuel cell stack coolant is not low:
Have the vehicle inspected at the nearest Toyota dealer.
Even if the fuel cell stack cool-
ant is low, do not refill it.