Quality Factor Volvo S60 I

Quality Factor

In a distributed system where information (signals) is sent between different control modules in a network, it is usually the control module that generates/creates information (the signal) that knows the quality of the information that is sent. To be able to inform receiving control modules about the quality of information, a quality factor (Q-factor) is sent over the network at the same time as the information (signal). The quality factor describes status of the information (signal). For example, if the signal is defective due to a faulty sensor, a receiving control module can use the quality factor to decide if the control module shall take any action (e.g., reconfiguration).

The quality factor can be of the following status

1. Ok The value indicates that the signal is normal and shows a credible status and accuracy.
2. Outside specified range Even though the value indicates that the signal is normal and may be usable, some fault has been detected that indicates that accuracy has been reduced so that performance may be affected or instability can occur.
3. No data found The value indicates that the signal has its initial start-up value and has not yet had time to receive measured or calculated value. This may occur when the control module's start-up process is not completely finished. As soon as the control module has started, the signal shall have a correct value. Receiving control module has a built-in delay to wait for correct signal.
4. No data exists The value indicates that the signal is faulty. This prevents the signal from being used by receiving control modules.

Summary of quality factor that may apply.

* Diagnostic trouble code may be stored.

The units must "speak" the same language and must be compatible with each other. A standardized communication protocol is used for this.

Signal configuration (sfg) contains the language between the modules. If any module has a signal configuration which does not tally with other modules, this module is unable to communicate with other modules. This means that all modules must have compatible signal configuration. The signal configuration is sometimes changed as new messages are added and old ones are deleted.

Instructions for the following are downloaded when a system is configured

1. Which control modules are included in the system (for example central electronic module (CEM), and others.)
2. Which control module should do what (for example "you are the control module for the driver's door - you are the control module for the passenger door")
3. Which functions should be included (for example if the alarm function should be on or off)
4. Which components are connected to the control modules (for example whether the inclination sensor is included in the alarm or not)
5. Which messages a control module is to transmit and which it is to receive
6. Where the different data should be stored.

In the central electronic module (CEM), information is stored on which control modules are installed in this particular vehicle. This information is stored and retrieved from Volvo's central database when software is downloaded. The central electronic module (CEM) also contains information on which primary signal configuration is to be used in the vehicle. Information on the vehicle's signal configuration must be stored in all control modules connected to the CAN network so that they can communicate in the first place.

The signal configuration is a part of the software downloaded after a control module is fitted or replaced. When software is loaded to a control module, the information in the control module indicating, for example, that a new accessory has been connected is updated automatically.

Once software has been downloaded, some values may be changed according to the customer's requirements, for example whether lamp indication upon locking or unlocking the vehicle should be active, or the dip degree of the interior rear view mirror. These settings may disappear when new software is downloaded.

Software is downloaded via the Software Manager.

Note. Even if two vehicles appear identical they may behave differently due to differing configurations, a parameter may have been modified by, e.g., the customer or workshop.

The network is made up of a number of control modules (sometimes called nodes) which are connected to each other serially via two communication cables. Each control module is supplied with power and grounded individually and receives messages /commands via the two communication cables. In both networks (high and low speed sides) the control modules are serially connected. In the event of an open-circuit those control modules beyond the open-circuit will not be able to communicate with other parts of the network.

Scheme 416

The network consists of two parts: a high speed side (HS CAN) which transmits signals/messages between the central electronic module (CEM) and control modules mainly in the engine compartment, and a low speed side (LS CAN) which transmits signals/messages between the central electronic module (CEM) and control modules in the passenger compartment and the luggage compartment.

The interface between the high and low speed sides is supplied by the central electronic module (CEM) which converts the transmission speed up or down for communication between the two network sides.

Scheme 417

The data link connector is located in the passenger compartment near the driver's station, cables for high-speed side (HS CAN) and low-speed side (LS CAN) are connected to the data link connector.

Scheme 418

1. Pin 3 LS CAN (low-speed side) (H-cable)
2. Pin 4 Chassis ground
3. Pin 5 Signal ground
4. Pin 6 HS CAN (high-speed side) (H-cable)
5. Pin 11 LS CAN (low-speed side) (L-cable)
6. Pin 14 HS CAN (high-speed side) (L-cable)
7. Pin 16 Voltage feed

Note. The data link connector's other connections may be used by other functions. This section only describes connections related to CAN.

The Volvo Controller area network (CAN) has two transfer speeds.

1. HS CAN (high speed) has a transfer rate of 500 kbit/s.
2. LS CAN (low speed) has a transfer rate of 125 kbit/s.

1 kbit/s = 1024 bits per second (1 byte = 8 bits).

For serial communication (Volcano Lite) between a control module and a slave control module the transfer rate is 10.4 kbit/s.

There is another serial standard known as LIN. This is an international standard which is becoming more commonly used. Its function is almost identical to that of Volcano Lite. The difference is in the communication method and rate. The transfer rate for LIN is 9.6 kbit/s.

High-speed net HS CAN (High Speed), example

Scheme 419

Low-speed net LS CAN (Low Speed), example

Scheme 420

To prevent electrical reflections and interference in the CAN network, there are terminating resistors which bridge CAN H (High) and CAN L (Low), one at each end (main line) on both the high and low speed sides of the network. Each terminating resistor has a resistance of 120 ohm

1. For HS CAN (high speed), the terminating resistors are located in the brake control module (BCM) and the engine control module (ECM).
2. For LS CAN (low speed), the terminating resistors are located in the upper electronic module (UEM) and the rear electronic module (REM).

Resistance measurement of parallel circuit with terminating resistor

Both the terminating resistors create a parallel circuit The following resistors can be measured under specified conditions

1. When the CAN network is intact, the resistance on the network is approx. 60 ohm.
2. In case of open circuits on the cables, so that 1 terminating resistor is not included in the circuit, the resistance in the net is approx. 120 ohm (only one main line is measured)
3. An open circuit on the cables to control modules located "outside" the measured circuit cannot be detected with this measurement.
4. In case of short-circuiting between the communication cables, the resistance is approx. 0 ohm between the cables, regardless of where the short-circuiting is located.

Scheme 421

Scheme 422

Scheme 423

The number of control modules in the CAN network varies depending on the car model, equipment level and structure week, The structure week and construction week are not necessarily the same week. The construction week is the week in which the vehicle is built in the factory. The content of the vehicle is steered towards structure week. A structure week may extend over a number of construction weeks. Structure weeks are specified in the format YYYYWW.

For example, structure week 199815 indicates that the structure week of the vehicle is week 15, year 1998.

Note. To troubleshoot respective CAN-net, see troubleshooting for CAN-related diagnostic trouble codes for Central electronic module (CEM). For example, choose any of CEM-DF01 - DF17 depending on CAN-net.

The CAN network is monitored by the central electronic module (CEM). When the central electronic module (CEM) detects a fault in the CAN network, a diagnostic trouble code (DTC) is stored in the central electronic module (CEM). There are various types of diagnostic trouble code (DTC), depending on the type of fault.

Types of error which are handled are

1. Electrical faults
2. No communication from the control module
3. Faulty communication.

Note. To troubleshoot respective CAN-net, see troubleshooting for CAN-related diagnostic trouble codes for Central electronic module (CEM). For example, choose any of CEM-DF01 - DF17 depending on CAN-net.

When there is a fault in the signal levels on the communication wire to the central electronic module (CEM), a diagnostic trouble code (DTC) is stored in the central electronic module (CEM). Each individual communication wire to the central electronic module (CEM), CAN L and CAN H on the low speed side of the network and CAN L and CAN H on the high speed side of the network, is checked. There are two different levels detected on each wire: short-circuit to voltage or short-circuit to earth. As the central electronic module (CEM) can also determine when a short-circuit on one or more wires takes place, the control module can also detect a short-circuit between the two CAN wires in the same part of the network.

This gives eight diagnostic trouble codes for detecting electrical faults.

HINT: The central electronic module (CEM) is unable to store diagnostic trouble codes (DTCs) for open-circuits on the CAN wires. Other diagnostic trouble codes (DTCs) may, however, be stored on account of this.

The central electronic module (CEM) knows which control modules should be present in the CAN network and checks at regular intervals to ensure that all control modules are communicating. If any control module in the CAN network is not communicating, a diagnostic trouble code (DTC) is stored in the central electronic module (CEM). There is a specific diagnostic trouble code (DTC) for every control module in the CAN network.

Every control module, apart from the central electronic module (CEM), has two diagnostic trouble code (DTC) types which relate to faulty communication (the central electronic module (CEM) has only one diagnostic trouble code (DTC) type).

These are

1. Faulty messages
2. Configuration error (not present on the central electronic module (CEM)).

Diagnostic trouble code (DTC) for faulty configuration is missing from the Central electronic module (CEM) since the control module is always the main control module in the network.

Faulty messages

When a control module transmits faulty signals in its messages a number of times, the control module shuts down communication. This is referred to as the control module going to "Bus-off". A diagnostic trouble code (DTC) is stored in the control module that transmitted faulty messages, and the control module stops communicating on the CAN network. This is done so that the control module does not interfere with other communication on the CAN network. If the fault is permanent, it is not possible to communicate with the control module and there is no chance of reading diagnostic trouble codes (DTCs) from the control module that has shut down communication as long as the control module continues to be powered. If the control module which stored a diagnostic trouble code (DTC) is powered down (for example by switching off the ignition or if the fuse to the power feed is removed), the control module will attempt again to communicate when the control module is powered up again. When troubleshooting such faults, therefore, it is important to know what kind of power feed is used for the control module in question.

Configuration fault

The central electronic module (CEM) transmits at regular intervals a control message to all control modules on the CAN network, This message includes, among other things, the ID number of the signal configuration currently being used. The reason for this is that all control modules on the CAN network must have the same signal configuration if they are to be able to communicate.

If the ID number of a control module's signal configuration does not tally with the ID number transmitted by the central electronic module (CEM), a diagnostic trouble code (DTC) is stored in the control module with the faulty signal configuration.

The control module which stores the diagnostic trouble code (DTC) will stop communicating on the CAN network but will still monitor traffic and respond to diagnostics communication.

Increasing demands for further functionality in the vehicle, both statutory requirements and customers, have led to increased complexity in the vehicle.

This, in turn, has encouraged developments towards more flexible electrical systems. The CAN-net (Controller Area Network) is a result of this research. The network permits the transmission and receipt of a large number of different commands and messages on the same wiring. Earlier, every command or message required a separate cable. Using networks has allowed functionality to be expanded without increasing the number of cables.

The number of commands and messages which can be handled on the network depends on factors such as the network speed and the length of the message or command. The Volvo network which is based on a control area network (CAN), can transmit over 500 different signals and approximately 100 messages. These messages are also called frames. Each message can contain several signals, e.g., a message to Rear electronic module (REM) can contain all signals for how the tail lights should be lit.

Easier To Add Further Functions And Install Accessories.

Because the control modules in the network are already connected to each other and are easy to add more information to, all that is required is

1. to connect the sensors to the nearest control module
2. to connect the controlled component to the nearest control module
3. to download software to alter the configuration and programming of the network.

The length of the wiring and the number of components which are introduced with the vehicle are less than previously.

An example of this is the addition of cruise control for the car.

Before the introduction of the network the installation of control modules, switches, vacuum pumps, vacuum servos, hoses and cable harnesses was necessary.

With the network only the installation of a switch and the downloading of software which alters the configuration of the vehicle is required.

Easier To Introduce Logical Functions.

Logical functions can be explained as "If this occurs then the following corrective action must be carried out". For example, the system is programmed so that if a tail light is broken, a message is transmitted via the control area network (CAN) to the driver information module (DIM) to warn the driver.

The only thing you need to do to introduce a logical function is alter the programming of control modules affected - the rear electronic module (REM) and the driver information module (DIM) in the example above.

Introduction of logic functions does not increase the number of components or cables.

Easy To Adapt The System To Customer And Market Requirements.

The functions can be altered depending on the requirements/demands of the customer and market. An example of this could be fog tail lamps. Certain markets use two fog tail lamps, others only use one on the driver's side. Previously it was required that different replacement parts were stored for different markets. Now the same replacement part can be used for all markets, by changing the programming depending on the market.

A Similar Basic System Can Be Used For A Whole Model Program.

Similar networks (hardware) can be used for a large number of different vehicles.

The only thing that differentiates the vehicles is

1. the components (control modules, sensors controlled components etc.) which are connected to the system
2. Which components do what.
3. Which components/functions are standard /optional/accessories
4. Configuration/programming of the system

Scheme 424

The data transmitted from the GPS antenna to the RTI control module consists of signals received from GPS satellites.

There is a signal booster (antenna amplifier) integrated in the GPS antenna. The signal is strengthened before it is transmitted to the GPS receiver which is integrated in the RTI unit. The GPS also adapts the impedance of the signal.

The RTI system and the GPS antenna require contact with at least three satellites to be able to calculate the position of the car. The RTI system can communicate with up to eight satellites at the same time.

The position calculated from the GPS satellites is accurate to within +/- 30 meters.

View the GPS information under system settings to check how many satellites are available.

The power supply is from the RTI control module. The power supply uses the same high frequency wiring as the GPS information that is sent to the RTI unit.

The GPS antenna is located in the parcel shelf in S80 and S60 models.

Note. If there is no GPS signal, the signal should be checked outside. The signal may be blocked if the car is indoors. Large objects on the parcel shelf or tinted rear windshields may also be the cause.

Scheme 425

The role of the TV receiver is to manage the incoming TV signals from local TV transmitters.

There are three models of the TV receiver

1. One for Europe (PAL)
2. One for U.S.A. (NTSC), only applies to the S80 Executive
3. One for Japan (NTSC).

The European TV receiver can handle three different PAL systems. The menu system on the TV receiver is used to change the PAL system settings.

The TV receiver sends the received TV signals on a serial bus (Melbus) to the RTI system. The RTI system handles the incoming signals and sends them to the display screen.

The TV receiver transmits the TV sound on a serial bus (Melbus) to the audio module via the RTI unit.

Station settings, color, TV picture size and the screen contrast are set using the audio module or the remote control.

The TV receiver is located in the left section of the cargo compartment in the S80 and S60.

Scheme 426

The role of the RTI control module is to calculate the position of the car based on the signals it receives from the GPS antenna, the speed signal from the central electronic module, the gear position and the gyro. The RTI system then works out a route for the selected destination.

There are two models of the RTI system, one old and one new version.

The older system has two units, the RTI control unit and the CD changer. In the new system the CD changer has been replaced by a DVD player which is integrated with the RTI control module.

There is an integrated three dimensional piezo electrical gyro in the RTI control module. This manages data about the movements of the car, such as whether any turnings are made.

Data transmitted on the CAN to the RTI unit from different nodes is

1. vehicle speed
2. wheel rotation counter
3. back-up (reverse) gear position
4. signals from the steering wheel controls
5. radio mute
6. background lighting.

Gyro and wheel rotation counters are used to calculate the position of the car for shorter periods, if communication with the GPS satellites is lost in a tunnel for example or to assist when there is no GPS signal.

Used in conjunction with map matching, GPS navigation, the gyro and the speed signal, the position can be calculated to an accuracy of +/- 10 meters from the position indicated on the screen.

The traffic message channel (TMC) receiver is integrated in the RTI unit. TMC is a standardized code system for traffic messages such as road works. The Japanese equivalent is called FM multiplex.

There Is No Traffic Information System In The USA.

The TMC antenna is located in the right-hand section of the rear bumper.

The control module is located on the left-hand side of the cargo compartment.

The RTI (road traffic information) control module can be diagnosed.