Warning lights on 7.5ton Mercedes truck

[peewhitt3rd]

A red warning light with"!" appears when I press the brake pedal. Have checked for leakages and loose tubes etc. Does anyone know what might be causeing this

[TWR]

Pad on the front?

[connor91]

if this truck has air brakes,could be water in system.pull the tap under the air tank.

con.

[douglas9401]

If it happens when the truck is moving it may be the warning light to indicate that the cab isn't locating tightly enough in place when locked down after maintenance.
I had this experience with a M.A.N. 7.5 tonner.