Traction Control Module: Description and Operation

Control Module for the Steering Wheel Angle Sensor

System Overview

Control module







1. Control module for the steering wheel angle sensor
2. Steering wheel angle sensor
3. Reference groove
4. Encoder for steering movements.

Only cars equipped with DSTC (dynamic stability and traction control) have a steering wheel angle sensor control module. The easiest way to determine if a car is equipped with DSTC (Dynamic stability and traction control) is to search for a switch, marked DSTC, positioned in the panel on the climate control module.

The Steering wheel Angle Sensor Module is positioned on the side of the central electronic module. The only function of the steering wheel angle sensor is to process the signals from the steering wheel angle sensor. The signals used by the DSTC system. The steering wheel angle sensor is mounted on the steering wheel module and is directly connected to the steering angle sensor via a connector on the steering wheel module. The Steering wheel angle sensor control module transmits signal information via the high-speed side of the Controller area network (CAN) to the brake control module, model year 2002- or the ABS control module, model year 1999-2001.

If a fault occurs the control module for the steering angle sensor detects this and a diagnostic trouble code (DTC) is stored at the same time as the DSTC function is switched off.

Diagnostic trouble codes (DTCs) stored in the control module for the steering wheel angle sensor. This information can be read off using the diagnostic tool via the data link connector (DLC) in the car.

Signals for the control module for the steering wheel angle sensor







The table above summarizes input and output signals to and from the Steering wheel angle sensor control module. The signal types are divided into directly connected signals, serial communication and Controller area network (CAN) communication.

Design

Control module for the steering wheel angle sensor







After initiation, with the ignition key in position II and when the steering wheel is turned 4.5 degrees in any direction, the control module for the steering wheel angle sensor continuously transmits information about the steering wheel angle position to the brake control unit to calculate the driving style of the driver. The brake control module was called ABS-control module up to and including model year 2001.

Communication between the Steering wheel angle sensor control module and the brake control module occurs on the high speed side of the Controller area network (CAN). The control module for the steering wheel angle sensor is positioned on a bracket inside the central electronic module.

The control module for the steering wheel angle sensor is supplied with power from the overload relay.

Steering wheel angle sensor







The steering wheel angle sensor is incorporated with the SRS contact reel, which in turn is installed on the steering wheel module. The steering wheel angle sensor is equipped with a disc with two code paths. Two circuits with light diodes read off a code path each. One circuit measures the steering angle up to 360 degrees and the other records how many complete turns the steering wheel has turned. Both circuits measure within ±700 degrees with a precision of 4.5 degrees. This information is transmitted to the control module for the Steering wheel angle sensor as digital signals.

Due to the reliance of the DSTC (Dynamic stability and traction control) on information from the steering angle sensor it is extremely important that the contact reel has been centered correctly and that only an original Volvo steering wheel is used.

Function
For information regarding the brake control module or ABS control module, refer DSTC (Dynamic stability and traction control) in Brake Control System.

SAS Diagnostic Functions

General








The control unit has built-in diagnostics, Volvo Diagnostics, which continually monitor the unit and the input and output signals.

Diagnostic trouble codes
If the control unit detects a fault, it stores a diagnostic trouble code. If, for any reason, a fault disappears after the diagnostic trouble code has been permanently stored in the control unit, information about the trouble code still remains in the control unit.

Reading and erasing diagnostic trouble codes
Stored diagnostic trouble codes can be read from the control unit using this facility.

Diagnostic trouble codes may be erased but only after they have been read at least once.

Reading input and output signals
Status of control unit input and output signals can be continually read using this facility.

Reading the control unit identity
VADIS identifies control units by reading the number of codes from the control unit memory. The codes contain information on the control unit as follows:
- hardware component number (control units without software)
- software component number (control units without software)
- software component number
- diagnostic software component number.

Software Downloading
New software can be downloaded into the control module for the Steering wheel angle sensor. When ordering software, the hardware and the software in the car is compared to the Volvo central database. If the comparison is OK the software is downloaded to the control module. If the comparison between the car and Volvo central database is not OK, the database is updated with the car configuration. When this is complete the software is downloaded.