Active brake booster
Along with its normal task of increasing the force that is applied to the clutch pedal, due to the vacuum created by the intake manifold or vacuum pump, the brake booster also creates the pre-pressure necessary for the operation of the ESP. The need for pre-pressure is caused by the fact that the return pump does not always have enough power to build up the required pressure due to the high viscosity of the brake fluid at low temperatures. When it becomes necessary to operate the ESP system, at the signal of the control unit, the electromagnet coil moves the metal core forward and opens the valves inside the valve assembly. At the same time, as when the brake pedal is pressed, pressure in chamber 1 increases due to the communication with the atmosphere (chamber 2 is still underpressure), while the booster creates a pressure controlled by two sensors in the brake system.
Sensor 1 (G201) and sensor 2 (G204) duplicate each other in order to ensure maximum reliability. These are capacitive sensors in the form of plate capacitors. When the pressure in the brake system acts on the movable plate, the distance between the two plates decreases and the capacitance of the capacitor increases. The change in capacitance is directly proportional to the change in pressure and is used to calculate the braking forces and control the pumping.
Used ABS with EDS/ASR/ESP J104
Used ABS/EDS 3104 combined in one unit with a hydraulic unit. Both units can be replaced individually without removing the entire assembly.
Tasks: control of ESP, ABS, EDS, ASR, EBV and MSR functions; constant monitoring of all electrical components; assistance in diagnostics during repair work.
Brake light off relay J508
When the ESP system activates the solenoid coil, the brake pedal may move enough to close the brake light switch. In order not to mislead other road users once again, relay 3508 disconnects the connection to the lamps while the electromagnet coil is turned on.
Steering angle sender G85
The spiral cable of the slip ring assembly connects the airbag control unit and the airbag module in the steering wheel. The steering wheel angle sender G85 is also installed in the housing of the slip ring assembly. It transmits information about the value of the angle of rotation to the control unit 3104 via the CAN bus. After replacing the coiled airbag cable/steering angle sensor, you must U carry out the basic installation. The G200 and G202 sensors are mounted on a common bracket, which is located near the vehicle's center of gravity, on the tunnel between the center console and the bulkhead of the engine compartment.
Lateral acceleration sensor G200
Measures lateral acceleration.
Yaw Angle Sensor G202
Measures the yaw angle of the vehicle (angle of rotation around the vertical axis). The signals from both sensors are needed by the control unit J104 to determine the actual state of the vehicle. With their help, the values of the control actions necessary to give the car proper stability are calculated.
Key ASR E256
On the Audi A2, there is no way to disable ESP. ASR can be turned off with the key (at a speed of 50 km/h).
New active ABS sensor
A sensor is said to be active when it requires external power to operate. The active speed sensor has a magnetoresistive element, the resistance of which varies depending on the magnetic lines of force formed by the track of the sensor's driving rotor. The master rotor of the sensor is mounted on the wheel hub and consists of a track with sensitive areas, magnetized element in opposite directions. The ring rotates in front of the fixed sensing element.
The principle of operation of the active sensor
In the immediate vicinity of the magnetized area, the magnetic lines of force are perpendicular to the track. Depending on the pole facing the sensor, they are directed either towards the sensor or away from it. Since the gap between the track and the sensor is very small, the field lines pass through the sensing element and change its resistance. An electronic amplifier/trigger circuit built into the sensor converts changes in resistance into two different levels of current. That is, when the resistance of the sensing element increases under the influence of magnetic lines of force passing through it, the current drops. When the direction of the field lines is reversed and the resistance decreases, the current increases. Since the north and south poles facing the sensor on a rotating track constantly replace each other, a periodic rectangular signal is formed, the frequency of which is proportional to the speed of the wheel.
Advantages: Wheel speed can be measured in any range from 0 km/h. The direction of rotation of the wheel is recognized. High resistance to corrosion. Compactness.
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