Mercedes-Benz S-Class Saloon W223 2021 Owner's Manual page 542

540 Display messages and warning/indicator lamps
Display messages
!
Parking brake Switch on
vehicle to release
J
Brake immediately
J
Check brake fluid level
Possible causes/consequences and
* The red ! indicator lamp is lit.
You have attempted to release the electric parking brake with the ignition switched off.
Switch on the ignition.
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* A malfunction has occurred while the HOLD function was activated.
A horn may also sound at regular intervals.
You cannot start the engine.
Immediately depress the brake pedal firmly until the display message disappears.
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You can restart the engine.
* There is insufficient brake fluid in the brake fluid reservoir.
& WARNING Risk of an accident due to low brake fluid level
If the brake fluid level is too low, the braking effect and the braking characteristics may be impaired.
Stop the vehicle as soon as possible, paying attention to road and traffic conditions. Do not continue driving.
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Consult a qualified specialist workshop.
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Do not top up the brake fluid.
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Solutions
M
P223 0288 02