FORD SCORPIO models up to 1/92 are equipped with TEVES MK II ABS brakes. From 2/92, the cars are equipped with TEVES MK IV ABS brakes (models with a 2.9-liter 24-valve engine and a diesel engine from 2/92 to 8/94 were equipped with upgraded TEVES MK II brakes).
The TEVES MK II brake system operates with a hydraulic unit, which replaces the conventional master cylinder with a vacuum-operated brake booster.
The TEVES MK IV brake system consists of a conventional main brake cylinder with a vacuum-operated brake booster and a separate, electronically controlled valve block with a pump
ABS prevents the wheels from locking during sudden braking. Thanks to this, the car remains controllable during sudden braking until a complete stop.
The speed of the wheels is measured using speed sensors installed on each wheel. Based on the signals from the individual sensors, the electronic control unit calculates an average speed, which roughly corresponds to the average speed of the vehicle. By comparing the speed of an individual wheel with the average speed of all wheels, the control unit determines the slippage of an individual wheel and thus determines how close this wheel is to locking. As soon as a wheel approaches locking, the hydraulic system keeps the fluid pressure constant based on the signals from the control unit. This means that the pressure in the brake caliper does not increase even when the brake pedal is pressed even harder. If the tendency to lock continues, the fluid pressure is reduced by opening the release valve. However, it is only reduced enough for the wheel to accelerate slightly, after which the pressure is again maintained constant.
The rear wheels have common control, the pressure in the hydraulic system is determined by the rear wheel with the greatest tendency to slip.
If the wheel acceleration exceeds a certain value, the pressure in the hydraulic system begins to increase again, but not above the value present in the entire system.
This process is repeated under hard braking for each wheel until the brake pedal is released or until the vehicle reaches a near-standstill (5-7 km/h).
ASR/EBV systems on vehicles from 9/94
ASR (Antriebsschlupfregelung) system: with the help of an electronic system for regulating the slip of the drive wheels during acceleration, the slipping wheel is braked and the torque is directed to the wheels that have traction with the road surface.
The electronic system monitors the slip of wheels prone to slipping and reacts instantly and individually by immediately generating and directly modulating the brake pressure on the wheels in question. This ensures that the maximum tractive force is always used, even on just one wheel in extreme cases. The independently operating ASR system uses many ABS components. The system operates during acceleration and is automatically switched off when the vehicle reaches a speed of 50 km/h. The particular advantage of this method of improving traction is that it has no negative effect on either the vehicle's driving dynamics or on the driving comfort of the vehicle.
The EBV system (electronic brake force distribution) distributes the brake force to the rear wheels using the hydraulics of the ABS system. Since the electronic control of the EBV system is more sensitive than the mechanically acting brake force regulator, the control range becomes significantly wider.
When driving in a straight line, the rear brakes absorb the full braking load. In order to ensure the vehicle's stability when braking on a bend, the braking effect of the rear axle must be reduced. The EBV system uses the ABS speed sensors to determine whether the vehicle is driving straight or on a curve. When driving on a curve, the braking pressure for the rear axle is reduced. This allows the rear wheels to absorb the maximum lateral force.
Instructions regarding ABS/EBV/ASR systems
The battery switch in the electronic control unit ensures that in the event of a defect (e.g. a broken wire) or if the operating voltage is too low (battery voltage below 10.5 volts), the ABS switches itself off. In this case, a yellow warning light comes on on the instrument panel while driving indicating that the ABS is switched off. At the same time, the EBV system is also deactivated. The normal braking system remains operational. In this case, the vehicle behaves when braking as if the ABS system was not installed on it.
Safety instructions: If the red brake system indicator lights up on the instrument panel while driving, stop the car immediately and find out the cause. The indicator may light up, for example, if there is insufficient brake fluid or the handbrake is applied. If the EBV system fails, the yellow ABS indicator and the red brake system indicator light up simultaneously - in this case, the rear wheels may lock up during sudden braking.
If the ABS indicator lights up on the instrument panel while driving, you must do the following:
- Stop the car quickly, turn off the engine and start it again.
- Check the battery voltage. If the voltage is less than 10.5 volts, charge the battery.
Note: If the indicator comes on at the start of a trip and goes out after a while, this indicates that the battery voltage was initially insufficient and then increased as a result of charging from the generator.
Check that the battery terminals are tight enough and have good contact.
Raise the car on jacks, remove the wheels. Check the electrical wires of the wheel speed sensors for external damage (fraying). Other ABS/EBV/ASR checks should be entrusted to a service station. The car's electronics are equipped with a self-diagnostic system that stores codes for any malfunctions that occur. At a service station, these codes can be read and the malfunctions can be eliminated.
Caution: Before carrying out welding work using an electric welding machine, it is necessary to disconnect the plug connector of the ABS control unit (location: near the hydraulic unit). Only disconnect the plug with the ignition switched off. During painting work, the control unit may be exposed to a maximum temperature of +90°C.