Bus and Diagnostics Communication: Overview Saab 9-5 I рестайлинг 2

System overview, function

LHD

Scheme 1

RHD

Scheme 2

For further information, see the following

P-BUS AND I-BUS

BUS DIAGNOSIS

SYSTEM OVERVIEW, COMPONENTS CONNECTED TO K-LEAD, PETROL

LHD

Scheme 3

RHD

Scheme 4

For further information, see the following

P-BUS AND I-BUS

BUS DIAGNOSIS

SYSTEM OVERVIEW, COMPONENTS CONNECTED TO K-LEAD, DIESEL

Scheme 5

1. Engine management system, ECM (589/595)
2. TCM (Transmission Control Module), control module for automatic gearbox (502)
3. ESP (Stabilizer system) (671)
4. Steering angle sensor, SAS (657)
5. MIU (Main Instrument Unit) (540)

Scheme 6

1. MIU (Main Instrument Unit) (540)
2. TWICE (Theft Warning Integrated Central Electronics) (632)
3. ACC (Automatic Climate Control) (216)
4. Head unit, audio/navigation (IHU) (635)
5. CDC (CD changer) (355)
6. PSM (Power Seat Memory) (357Dk)
7. PMM (Power Mirror Memory), door mirror memory (611)
8. DICE (Dashboard Integrated Central Electronics) (628)
9. Airbag control module (ACM) (331)
10. SPA (Saab Parking Assistance) (630)
11. SID control module (541)

Scheme 7

1. SID control module (541)
2. Audio system, head unit (EHU) (353)
3. Radio receiver, satellite radio (SDAR) (349)
4. Control module, On-Star (673)
5. Data link connector (445)

Scheme 8

1. DICE (Dashboard Integrated Central Electronics) (628)
2. Data link connector (H16-5/445)
3. ESP (Electronic Stability Program) (671)
4. AHL control module (Automatic Headlamp Levelling) (664) in headlamps with xenon lamp

Scheme 9

1. DICE (Dashboard Integrated Central Electronics) (628)
2. Data link connector (H16-5/445)
3. AHL control module (Automatic Headlamp Levelling) (664) in headlamps with xenon lamp
4. DAH (Diesel Additional Heater) for cars with diesel engines (597)
5. ESP control module (Electronic Stability Program) (671)
6. Diesel engine control module EDC 16 (595)

Scheme 10

Scheme 11

A BUS is understood to be the leads over which information is sent digitally and serially. Digital means that the voltage difference between the leads has only two values, roughly 0 V and 5 V. The information is coded so that different combinations of pulses between 0 V and 5 V have different meanings.

Serial means that the information is sent in "packets" which are transmitted one after the other in rapid succession.

All control modules in the Saab 9-5 have a BUS connection except for the DAH, AHL and On-Star.

The BUS is divided into the P-BUS (powertrain BUS) and (single lead and dual lead) I-BUS (instrument BUS).

The P-BUS and the dual-lead I-BUS are connected to the main instrument unit (MIU). The two I-buses - the single-lead I-BUS and the dual-lead I-BUS - are connected to the SID control module. The different buses are electrically separate in the MIU and the SID control module.

The diagnostic tool does not have a direct BUS connection with either the P-BUS or the 2-lead I-BUS but communicates with the connected control modules via DICE. The diagnostic tool communicates directly on the 1-lead I-BUS with the connected control modules EHU and SDAR.

The data transfer rate of the P-BUS is ten to fifteen times faster than that of the I-BUS. The reason for this is that the powertrain systems need information with the least possible delay, as for example when providing air mass compensation when the selector lever is moved from N to D or torque limitation in connection with gear changing.

All information transmitted by a control module can be accessed by all other control modules connected to the BUS. The MIU and SID control modules are responsible for ensuring that information accessible to the control modules of any of the buses is also available to the other BUS-connected control modules. MIU is connected to both the P-BUS and the dual-lead I-BUS. MIU serves as a gateway between the P-BUS and the I-BUS. The SID control module is connected to both the dual-lead and the single-lead I-BUS. The SID control module serves as a gateway between the two I-buses.

Vehicle speed is an important parameter for many control modules. The MIU receives vehicle speed information from the ESP control module via the P-BUS. The MIU transmits speed information on the 2-lead I-BUS and the SID control module ensures that the EHU has access to the information on the 1-lead I-BUS.

The control modules send out information on the BUS at regular intervals. The time between two transmissions depends on the information being sent and varies between 10 milliseconds (0.010 seconds) and 1 second. Information is also sent out by the control modules whenever the information changes.

The transfer of information between the control modules takes place on one lead for the 1-wire I-BUS or on two leads for the P-BUS and the 2-wire I-BUS. On the BUS with two leads both are twisted to reduce sensitivity to electrical interference.

Scheme 12

The BUS may be regarded as a telephone line running between the control modules. Communication is continuous once the ignition switched on. With the ignition switched off, a control module that is operative may if necessary awaken the other control modules. This happens for example when a door is opened and TWICE, to which the door switches are connected, awakens the others so that DICE will be able to switch on the interior lighting.

When one of the control module microprocessors "speaks" the other control modules listen regardless of whether or not the information is of interest to them. The MIU and SID control modules transfer information, as appropriate, between the buses. This way, information sent by one control module is available to all control modules connected to the BUS.

With the BUS system, analogue signal leads such as those for the turbo/APC pressure signal for the MIU, and digital signal leads such as those for PWM throttle position signals and frequency modulated engine speed signals, can be eliminated and the number of sensors consequently reduced.

The Trionic system, which is connected to a BUS, has a coolant temperature sensor. This means that the temperature of the coolant is always available to all systems. For this reason, only one coolant temperature sensor is needed in the car.

The coolant temperature is used by DICE for controlling the radiator fans (see illustration), by the MIU for controlling the temperature gauge, and by the ACC for controlling ventilation fan speed and air distribution during cold starts.

Basically, the control modules connected to a BUS are like one big control module with a number of sensors and a number of actuators. BUS communication may be regarded as internal control module communication.

This means that an overall view of the car is essential when carrying out fault diagnosis. A malfunction need not necessarily be caused by a fault in the system where it occurs but may very well be caused by a defective sensor in another system.

Scheme 13

Scheme 14

Scheme 15

A transmitting control module sends a message by transmitting ones or zeroes in a particular order. The control module only transmits if no other is transmitting. The ones and zeroes are transmitted according to a predetermined protocol so that all the control modules interpret the information in the same way. The message conveys what is being transmitted and the value thereof; e.g. "Coolant temperature 100°C", or "A/C ON".

The two BUS leads are supplied with approximately 2.5 V from each control module. The voltage is achieved by means of three resistors connected in series between 5V and ground. The middle resistor causes the voltage on BUS+ to be slightly lower than BUS - when no message is being transmitted.

When the voltage is about 2.5V on both leads during a specified interval (on the P-BUS, 2 millionths of a second) a one is transmitted. In order to send a zero, the control module pulls the BUS+ up to nearly 5V and pulls down BUS-almost to ground for the same length of time.

Note that a long series of ones is the same as not transmitting a message.