The residual height of the truck tire protective layer is 1.6 mm.
Pneumatic brake transmission pressure gauge does not work.✓Correct answer
In both cases.
Explanation
The gauge in a pneumatic brake system must work because it tells the driver whether enough air pressure is available for braking. A truck tread depth of 1.6 mm is not, by itself, below the applicable limit, so it is not the defect here.