ESP DESCRIPTION

2.0 16V JTD, 2.2 16V JTD · MY 2005

The vehicle is fitted with an ABS braking system which prevents the wheels from locking during braking, makes the best possible use of the grip conditions available and keeps the vehicle as easy as possible to control during emergency braking.

The ABS is an additional part of the basic braking system; it is disabled if there is a problem, with the braking system working the same way as for a vehicle without ABS.

The advantage of ABS over conventional systems is that it makes it possible to maintain maximum manoeuvrability even when braking hard in poor grip conditions, preventing the wheels from locking.

The system is completed by the EBD system (Electronic Brake Distributor) which distributes the brake force by means of the ABS sensors and control unit.

The "ABS failure" warning light and the "minimum brake fluid level" warning light coming on simultaneously with the engine running means that there is a problem with the EBD system; in this case, the wheels could lock during sharp braking.

The "ABS failure" warning light coming on by itself with the engine running usually means that there is a problem with the ABS only.

In this case, the braking system will work properly, just without the anti-lock function.

The operation of the EBD system may also be affected under these circumstances.

If the "minimum brake fluid level" warning light only comes on, this means that the hydraulic system fluid level is too low.

On this version, the system also includes the ESP function.

ESP (Electronic Stability Program) is an electronic system that controls the stability of the vehicle, intervening on the engine torque and introducing differentiated braking for the wheels in the case of a loss of grip restoring the vehicle to the correct path.

Whilst driving the vehicle is subject to lateral and longitudinal forces which can be controlled by the driver as long as the tyres hold the road sufficiently well; when this is no longer the case, the vehicle starts to drift from the desired path. Especially when driving on uneve road surfaces (such as cobblestones or where there is water, ice or soil), changes in speed (during acceleration or braking) and/or trajectory (bends or the need to avoid obstacles) can cause a loss in grip for the tyres.

When the sensors detect conditions that could lead to the vehicle slipping, the ESP system intervenes on the engine and the brakes producing a stabilizing torque.

The ESP system switches on automatically each time the engine is started up; it can be switched off and switched back on again manually by pressing the button on the left side of the dashboard.

The basic ESP system components are:

• the electronic control unit;
• the angular sensor detecting the position of the steering;
• four sensors which detect the rotation speed of each wheel (ABS sensors);
• the braking system pressure sensor;
• the slewing sensor which detects the rotation of the vehicle around the vertical axis;
• the sensor which detects lateral acceleration (centrifugal force).

Depending on the version, the system also includes other auxiliary functions:

TC (Traction Control) and ASR (Anti Slip Regulation) incorporated in the ESP system, control the vehicle traction and intervene automatically each time either one or both of the drive wheels are slipping, respectively.

Depending on the slipping conditions, two different control systems can be activated:

• if the slipping involves both drive wheels, caused by the excessive force transmitted, the ASR function intervenes, reducing the power transmitted by the engine;
• if the slipping only involves one of the drive wheels, the TC function intervenes, automatically braking the wheel that is slipping, with a similar effect to that of a self-locking (limited-slip) differential.

The MBA (Mechanic Brake Assistance) and HBA (Hydraulic Brake Assistance) functions are systems that provide an automatic increase in the braking pressure in emergency braking conditions. In effect, in critical situations, when the driver operates the brake pedal decisively, the system intervenes on the braking circuit, increasing braking pressure to ensure that the vehicle stops as quickly as possbile.

The two systems behave in the same way, the only difference being that the pressure increase setting in one case is regulated by the ABS - ESP system control unit and in the other case in a mechanical fashion.

The MSR function (Motor Schleppmoment Regelung) completes the system. This function automatically regulates the engine braking torque whilst changing down; if there is a sudden gear change down, it intervenes, supplying torque to the engine to prevent excessive drive at the drive wheels which, especially in poor grip conditions, could lead to a loss in stability of the vehicle.