Design

Design

Control module and ABS hydraulic modulator
The brake control module (BCM) is mounted on the hydraulic modulator in the engine compartment.
The control module is supplied with power via two fuses and connected to ground by two ground terminals.
There are diagnostics for the valve coils and the pump motor. There are three different versions of the brake control module (BCM).

ABS control module




The control module contains two different micro-processors which receive signals from different sensors in the system. The micro-processors operate in parallel and use a program to compute the necessary ABS and electronic brake force distribution functions. The ABS control module has eight valve coils for the hydraulic valves, four outlet valves and four inlet valves.
The control module has a connector for connection to the cable harness in the car.

Control module for STC and TRACS AWD




The control module for STC/TRACS AWD has twelve valve coils for the hydraulic valves. Otherwise its contents are the same as the control module for ABS. The four additional valve coils are used for stability and traction control.

Control module for DSTC




The control module for DSTC looks the same as an STC control module. However the software is different and it is connected to the brake pressure sensor.
When replacing a DSTC control module, the control module must be calibrated according to the information in VIDA vehicle communication.

ABS hydraulic modulator




There are four versions of the ABS hydraulic modulator:
- ABS
- STC
- DSTC
- TRACS AWD.
The ABS hydraulic modulator is located against the cowl panel in the engine compartment. The ABS hydraulic modulator consists of:
- hydraulic valves
- relief valves
- an integrated brake pressure sensor
- a pump motor.
The pump motor generates the brake pressure required during stability and traction control.
There are diagnostics for the hydraulic valves, brake pressure sensor and the pump motor.

Switch STC/DSTC (S40/V50 -2006)




The switch for STC and DSTC is on the tunnel console between the front seats. The STC or DSTC function is always engaged when the ignition is switched on. When the switch is activated, only stability control is disengaged. The switch has a green LED indicator which displays the ON position.
A message in the driver information module (DIM) confirms that the switch is activated or deactivated.
If a diagnostic trouble code (DTC) is stored in the brake control module (BCM), the status of the LED will still change if the switch is pressed. However no text message will be displayed in the driver information module (DIM) because the fault has deactivated the functions.

Control DSTC (C70 and C30/S40/V50 2007-)




Activation of DSTC is controlled by turning the control for the Steering wheel module (SWM). When the ignition is activated the DSTC function is always engaged. When selecting the DSTC function the on/off mode is available. When the control sets DSTC in mode on/off, this is confirmed by a message in the Driver information module (DIM).
If a diagnostic trouble code (DTC) is stored in the brake control module (BCM) a message is displayed in the Driver information module (DIM). The messages vary depending on whether the diagnostic trouble code (DTC) was stored when the DSTC function was active or inactive.

Warning lamps




The brake system uses five warning lamps and a text display in the driver information module (DIM).

ABS warning lamp (1)
The ABS warning lamp indicates a fault in the ABS system.

Brake warning lamp (2)
The brake warning lamp indicates:
- A fault in the electronic brake force distribution (EBD) function
- That the brake fluid level is too low (the signal is transmitted from the central electronic module (CEM) to the driver information module (DIM)).

General warning lamp (3)
Normally the general warning lamp lights together with the brake warning lamp.

Traction control warning lamp (4)
The traction control warning lamp flashes:
- When a drive wheel starts to spin during acceleration. Traction control is then activated to regain traction
- When a drive wheel starts to spin on a slippery surface. Stability control is then activated to regain traction
- When the lateral stability limit is exceeded (the car oversteers or understeers) during active yaw control.

Information lamp (5)
The information light comes on when:
- There is a fault with ABS, STC, DSTC or TRACS
- The brake disc temperature is too high.

Text display in the combined instrument panel
Displays information about faults in the brake system or other settings.

Note! The text may vary depending on the model year and equipment. It may also change as a result of software updates in the driver information module (DIM).

Wheel sensors




The wheel sensors are installed on the spindle joints of the front and rear wheels. The wheel sensors are active sensors. The task of the wheel sensors is to supply the control module with information about the rotation speed of each wheel. The control module uses the signal from the wheel sensors to calculate wheel speed and the acceleration and retardation of the car.
The wheel sensors are supplied with 12 V. When the magnetic pulse wheel rotates, the sensor generates a pulsed current (quadratic wave). The strength of the current depends on the position of the pulse wheel. The signals from the coil in the sensor are then affected by the resistor, which is sensitive to magnetic fields. This means that the output signal is a current which oscillates between 7 mA and 14 mA. The frequency increases with speed.
The magnetic pulse wheel is integrated into the inner wheel bearing seal and the wheel sensor is radially positioned in the shaft housing in relation to the magnetic pulse wheel. The rear wheel sensors are axially positioned in relation to the magnetic pulse wheel. Both the front and rear magnetic pulse wheels have 88 poles, 44 north poles and 44 south poles. In the event of a fault in any of the wheel sensors the following functions do not engage or are disengaged:
- ABS
- Stability control
- Traction control
- DSTC
- TRACS.
Electronic brake force distribution (EBD) is available if one wheel sensor is faulty. Electronic brake force distribution (EBD) is disengaged if there is a fault in more than one wheel sensor simultaneously.
The control module calculates the vehicle speed using the signals from the wheel sensors.
There are diagnostics for the wheel sensors.

Stop lamp switch




The brake light switch is located by the brake pedal lever. The stop (brake) lamp switch self-adjusts during installation. The brake control module (BCM) receives information about the status of the stop (brake) lamp switch via the engine control module (ECM). The stop (brake) lamp switch signal is used by the brake control module (BCM) to diagnose faults in the pedal position sensor. The signal is also used to disengage traction control if a fault is detected.
The stop (brake) lamp switch is supplied with power from the battery. When the switch is closed, the power for the signal is supplied through the engine control module (ECM). The engine control module (ECM) then transmits a signal via the Control area network (CAN) indicating that the stop (brake) lamp switch has been activated.
There are diagnostics for the stop (brake) lamp switch.

Pedal position sensor




The pedal position sensor is mounted on the power brake booster in the engine compartment. The sensor has several functions.
The sensor is used:
- by the engine control module (ECM) for cruise control. The signal is transmitted via the controller area network (CAN)
- to shut off traction control during braking (TRACS AWD only)
- to diagnose the function of the stop (brake) lamp switch (TRACS AWD only).
The sensor is affected by the push rod for the brake pedal. It is a sliding potentiometer.
Fault detection of the signal is between 0 V-0.15 V and 4.85 V-5.0 V. A diagnostic trouble code (DTC) is stored If the signal is between 0 V and 0.15 V. The sensor is considered not to be installed in the car. If the signal is between 4.85 V and 5.0 V, the sensor is understood to be pushed in excessively.

Body sensor cluster stability sensor (BSC) (DSTC only)




The body sensor cluster stability sensor (BSC) is under the right-hand front seat. The sensor is supplied with 12 V and is grounded in the brake control module (BCM). The information from the body sensor cluster stability sensor (BSC) is used for stability calculations in the brake control module (BCM). The body sensor cluster stability sensor (BSC) contains a yaw angle sensor which measures the yaw angle speed in °/s, and a lateral acceleration sensor which measures lateral acceleration in m/s2. The body sensor cluster stability sensor (BSC) for AWD also contains an acceleration sensor which measures longitudinal acceleration
The body sensor cluster stability sensor (BSC) communicates with the brake control module (BCM) via an internal controller area network (CAN).
The body sensor cluster stability sensor (BSC) can be diagnosed by the brake control module (BCM).
When replacing the body sensor cluster stability sensor (BSC), the brake control module (BCM) must be calibrated according to the information in VIDA vehicle communication or manually according to the test drive.