For vehicles with engines «M57», «M62» And «N62» a dynamic stability control system is installed - «DSC», which includes all the functions of the system» ABS/ASC+T».
The failure of any of these systems allows the car to move, but requires more attention to speed and traffic conditions, because. driving efficiency is drastically reduced.
Attention! All work on the system «ABS» carried out with the ignition off and the «–» terminal AB. Before work with the use of electric welding equipment, it is necessary to undock the ECU loop "ABS/ASC+T» («DSC»).
When painting a car, the maximum allowable drying temperature is not more than + 80°C, within two hours.
System «ABS/ASC+T» And «DSC» installed on the car increases the active safety of the car and prevents the wheels from locking during heavy braking and skidding in corners. At the same time, the car maintains controllability until it comes to a complete stop, without skidding. The system is automatically activated at speeds around 8 km/h and deactivated below 3 km/h.
Brake subsystem «ABS» works most efficiently with maximum tire friction on the road surface. For braking, the tire must transfer a certain amount of friction to the pavement, as a result of which it slides on the road surface. Thus, the circumferential speed of the wheel is made less than the speed of the vehicle. In a certain braking mode, the braking force transmitted by the wheel is of the greatest importance. However, when going beyond its limits, the wheel locks up and the friction force with the ground decreases.
Role «ABS» is to immediately limit and maintain the braking action of each wheel within the framework of the optimal braking mode when the condition of the road surface changes. Part «ABS» includes - standard braking system, wheel pulse generators (wheel speed sensors), hydraulic unit, electronic control unit and electrical wiring harness.
The pulse generator consists of a ring gear mounted on the wheel hub, which interacts with the Hall sensor. The frequency of the generated pulses corresponds to the wheel speed and enters the electronic control unit of the system «ABS» (ABS), where it is being processed. By comparing the speed of rotation of each wheel with the average speed of all wheels, the ABS-ECU determines the amount of slip of an individual wheel and thus can determine when one of them comes close to blocking.
And based on this information, it issues control pulses to the solenoid valves of the hydraulic unit (hydroblock). As soon as one of the wheels approaches blocking, the pressure of the brake fluid in its caliper becomes increased in relation to the grip of the tire with the road. The hydraulic system under the influence of control signals maintains the pressure of the brake fluid stable. This means that the pressure in the caliper does not increase even with further pressure on the brake pedal. If the risk of blockage persists, the pressure is reduced by opening the exhaust valve, but only to the point where the wheel begins to accelerate somewhat again, after which the pressure is again maintained constant.
If the wheel starts to turn faster, the ABS-ECU issues a signal to increase the pressure, but not higher than the total pressure in the brake system. The process of braking and releasing the wheel, when the brake pedal is pressed sharply, will be repeated until the brake pedal is released, or the vehicle speed drops to 2 - 3 km / h. The driver feels the action of the ABS by the pulsation of the brake pedal and the characteristic sound of the valve body in the engine compartment, which signals to him about the movement in the boundary conditions. This reminds him to slow down.
The valve body of the system is installed on the brake line after the main brake cylinder. A solenoid valve is installed on each of the four pipelines suitable for the valve body, which diverts the brake fluid to an electric pump that provides brake pressure in the line of a particular wheel. Checking the health of the ABS system is carried out using the indicator in the instrument cluster. The lamp lights up when the ignition is turned on, and goes out after 3 seconds. If the indicator continues to glow or lights up while driving, then you must:
- stop the car, turn off the engine and start it again;
- check the battery voltage, it must be at least 10.5 V;
- check the reliability of the AB contact connections;
- raise the car, remove the wheels, check the integrity of the wheel speed sensor harness.
In the event of a system failure «ABS», its ECU stops generating control pulses, and the car brakes according to the standard scheme (without regulation). Pilot lamp «ABS» in the instrument cluster is constantly lit. Subsystem «ASC+T» – drive wheel load control system, reduces the torque of both drive wheels when they slip, by reducing engine power. The system simultaneously acts on the brakes and additionally reduces engine power, through the powertrain control unit.
If the rear wheel shows a tendency to slip, the electronic engine management system (DME - Digital Engine Electronics) receives this information from the ECU «ABS/ASC+T». A short-term reduction in engine power is carried out by reducing the amount of fuel supplied, and on a cold engine, additionally by changing the ignition timing. This action of the system is equivalent to releasing the gas pedal.
If this is not enough, then the function intervenes in the braking process «T» (traction control), which performs dosed braking of the drive wheels.
Subsystem «ASC+T» allows you to eliminate wheel slip during acceleration and cornering in the entire speed range, tk. it has an integrated traction control. By applying engine braking, it prevents the drive wheels from locking up momentarily when driving on slippery roads. Up to 40 km/h traction control («T») can create the effect of a locked differential. Since the braking of the left and right wheels occurs independently of each other, the system «ASC+T» acts as a locking differential with almost 100% locking effect.
System «ASC+T» interlocked with the system «ABS» thanks to a single computer «ABS/ASC+T», which in turn is connected to the ECU-KSUD (DME-Motronic). System action «ASC+T» displayed by flashing control lamp «ABS» on the instrument panel.
System «ASC+T» turns on automatically after each engine start. When the ignition is switched on, the system performs a self-diagnosis, and the warning lamp lights up briefly «ABS». The system can be disabled by pressing the key «ASC» («DSC») on the center console (see fig. 1.56), the control indicator also lights up (14, see fig. 1.12). Repeated pressing of the key leads to the reverse switching on of the system, the control lamp goes out. When the lamp flashes, the system is adjusting traction based on actual driving and driving conditions.
If the control lamp does not go out after starting the engine or lights up constantly while driving, then a system malfunction is signaled «ASC+T» , while maintaining the functions of the brake system, but without regulation. By car, you can continue driving, but at a well-chosen speed and you need to contact the service station.
Attention! When driving in deep snow, with snow chains or when driving out of deep mud, it is advisable to deactivate the system «ASC+T» / «DSC».
System «DSC»
System «DSC» (Driving Stability Control - dynamic stability control) installed in combination with engines «M62» And «N62». It recognizes the car's tendency to buckling right from the start and stabilizes it on the road within milliseconds.