Steering Wheel Module (SWM)

System Overview

Control module







The steering wheel module (SWM) has the task of managing the signals for those functions which can be controlled via the steering wheel control stalks and buttons. The signals are transmitted to the relevant control modules via the control area network (CAN). The actual functions are not in the steering wheel module (SWM).

The steering wheel module (SWM) manages the control signals for the following functions:
- Volume control and CD track/radio selection
- Volume control during hands free carphone calls and menu selection for the phone module (PHM)
- Menu selection for traffic information
- Rear windshield wiper/washer
- Cruise control
- Turn signal lamps
- High and low beam
- Trip computer and displaying/erasing text messages in the driver information module (DIM).

The control module is integrated in the steering wheel bracket. The steering wheel must be removed to replace the control module. Control stalks, key pads and switches can be replaced as separate units.

Cars with DSTC also have a steering wheel angle sensor installed in the contact reel in the steering wheel module (SWM).

The steering wheel module (SWM) communicates with directly connected components and communicates with other control modules via the Control Area Network (CAN).

The control module checks activations and input and output signals via an integrated diagnostic system. A diagnostic trouble code (DTC) is stored if the control module detects an error. In certain cases the control module replaces the faulty signal with a substitute signal.

Any diagnostic trouble codes (DTCs) are stored in the control module memory. This information can be read off using VADIS/VIDA via the data link connector (DLC) in the car.

A simple way to ensure that the steering wheel module (SWM) is powered and grounded is to flash the headlamp high beam or to change the audio or carphone volume.

Signals
The below summarizes the input signals to and output signals from the steering wheel module (SWM). The signal types are divided into directly connected signals, serial communication and Controller area network (CAN) communication. The following illustration displays the same information with the Volvo component designations.










Design

Steering wheel buttons
The steering wheel buttons control functions and menu selection for:
- Traffic information (option)
- Audio (option)
- Carphone (option)
- Cruise control (option).

The signals from the steering wheel buttons are transmitted via serial communication.

The steering wheel buttons are connected in series to the steering wheel module (SWM) via contact reel in the steering wheel hub. The steering wheel buttons are connected in the following order, counted from the contact reel:
1. Cruise control
2. Audio/carphone
3. Traffic information.

There are diagnostics for the steering wheel buttons.

Function

Trip computer and displaying/erasing text messages







The left-hand control stalk is used to control the trip computer and to display and erase text messages in the driver information module (DIM) (5/1). The steering wheel module (SWM) (3/130) transmits information to the driver information module (DIM) on the Control area network (CAN) indicating which function is selected.

The trip computer menu is controlled using the ring on the left-hand control stalk. Turn the ring forwards or backwards to scroll through the menu one step at a time. Some menu selections, such as average speed and fuel consumption, can be reset using the RESET button.

Error messages displayed in the driver information module display are erased using the READ button.

Diagnostic functions

General
The control module has a built-in diagnostic system, Volvo Diagnostic, which continuously monitors internal functions as well as input and output signals.

Diagnostic trouble codes (DTCs)
A diagnostic trouble code (DTC) is stored if the control module detects a fault. 35 diagnostic trouble codes (DTCs) can be stored. A fault which is detected in the most recent operating cycle is defined as permanent. Other faults which are detected are defined as intermittent.

Reading and erasing diagnostic trouble codes (DTCs)
Stored diagnostic trouble codes (DTCs) can be read off and erased using this function. Diagnostic trouble codes (DTCs) can only be erased once all the diagnostic trouble codes (DTCs) have been read off at least once.

Reading off input and output signals
This function can be used to continuously read off the status of the control module's input and output signals.

Reading off extended diagnostic trouble code (DTC) information
This function can be used to read parameters, status identifiers and counters stored at the same time as a diagnostic trouble code (DTC). These are called frozen values.

Reading the control module identification
VADIS/VIDA identifies control modules by reading off a number of codes from the control module memory.
The codes contain the following information about the control module:
- hardware P/N (control module without software)
- hardware serial number (control module without software)
- software P/N
- diagnostic software P/N.

Downloading software and replacing the control module
New software can be downloaded into the steering wheel module (SWM). When ordering software, the hardware and the software in the car is compared to the data in 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.

The control module is integrated in the steering wheel bracket. The steering wheel must be removed to replace the control module.