Intervention by Electronic Stability Program during understeer or oversteer, function

Preconditions

 Vehicle speed is    20 km/h.

 The Electronic Stability Program (ESP®) is switched on, the ESP® shutoff indicator lamp and the ESP® indicator lamp in the instrument cluster control unit (ICUC) (A1) in vehicles with code J6A (Classic cockpit) or in the instrument cluster control unit screen (ICS) (A153) in vehicles with code J6B (Multimedia cockpit) or code J6C (Multimedia cockpit, interactive) are off.

Function

When driving, the electronic brake system control unit (EBS) (A10b) uses the signals from the following sensors to continuously record the specified course issued by the driver and compares it against the actual course:

 Steering wheel angle sensor (SAS) (B66)

 Left front axle rpm sensor (B13)

 Right front axle rpm sensor (B14)

 Left rear axle rpm sensor (B15)

 Right rear axle rpm sensor (B16)

The electronic brake system (EBS) control unit takes the vehicle speed into consideration to calculate the actual course using the signals supplied by the yaw rate and lateral acceleration sensors integrated into the Electronic Stability Program (ESP®) control unit (A25).

As soon as the electronic brake system (EBS) control unit detects a deviation between the specified course and the actual course, it triggers brake interventions at the individual wheels in order to correct the course.

 On vehicles with code A4B (Leading axle, 7.5 t, steered, relievable), code A4Q (Trailing axle, 9 t, steered, relievable, liftable), code A4R (Trailing axle, 9 t, steered, relievable), code A4T (Trailing axle, 8 t, steered, relievable, liftable), code A4U (Trailing axle, 8 t, steered, relievable), code A4X (Trailing axle, 7.5 t, steered, relievable), code A4Y (Trailing axle, 7.5 t, steered, relievable, liftable) or code JAVA (Leading axle 8 t, air-sprung and hydraulically steered):
If the additional steering axle (ASA) control unit (A34) registers a fault, the electronic brake system control unit (EBS) deactivates the control action and the ESP® indicator lamp in the instrument cluster control unit (ICUC) lights up on vehicles with code J6A (Classic cockpit) or in the instrument cluster control unit screen (ICS) on vehicles with code J6B (Multimedia cockpit) or code J6C (Multimedia cockpit, interactive).

Intervention by the brake system when understeering
If the towing vehicle breaks away at the front axle, a yaw torque is built up by selective braking of the rear wheel on the inside of the curve; this turns the towing vehicle into the curve in order to stabilize it. During an automatic brake application (arrow), the ESP® indicator lamp in the instrument cluster control unit (ICUC) lights up on vehicles with code J6A (Classic cockpit) or in the instrument cluster control unit screen (ICS) on vehicles with code J6B (Multimedia cockpit) or code J6C (Multimedia cockpit, interactive).

W42.45-1004-11

Intervention by the brake system when oversteering
If the towing vehicle breaks away at the rear axle, the oversteer handling characteristic is counteracted by specific braking of the front wheel on the outside of the curve. Simultaneously, the semitrailer is braked via the trailer control valve and jackknifing of the tractor/semitrailer combination is prevented by straightening the tractor/semitrailer combination. During an automatic brake application (arrow), the ESP® indicator lamp in the instrument cluster control unit (ICUC) lights up on vehicles with code J6A (Classic cockpit) or in the instrument cluster control unit screen (ICS) on vehicles with code J6B (Multimedia cockpit) or code J6C (Multimedia cockpit, interactive).

W42.45-1005-11