Bus communication

Bus communication

•	Trionic, engine management system (TRIONIC)

•	TCM (Transmission Control Module), control module for automatic transmission (502)

•	TC/ABS, (Traction Control) (382)

•	P-bus (Powertrain bus)

•	MIU (Main Instrument Unit) (540)

•	I-bus (Instrument bus)

•	SID (Saab Information Display) (541)

•	TWICE (Theft Warning Integrated Central Electronics) (632)

•	ACC (Automatic Climate Control) (216)

•	Audio system, main unit (353)

•	CDC (CD changer) (355)

•	PSM (Power Seat Memory) (357Dk)

•	PMM (Power Mirror Memory) (611)

•	DICE (Dashboard Integrated Central Electronics) (628)

•	Data link connector (H16-5/445)

•	Airbag (SRS) (331)

•	ABS (Anti-lock Brake System) (547)

•	SPA (Saab Parking Assistance) (630)

P-bus and I-bus

A bus is 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 0 V and 5 V pulses 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 are connected to the bus with the exception of ABS and SRS. For cars with Traction Control, the TC/ABS control module is connected to the P-bus.

The bus consists of a P-bus (Powertrain Bus) and an I-bus (Instrument Bus). Both buses are connected to the MIU (Main Instrument Unit). The buses are electrically isolated from each other.

The diagnostic tool is not connected directly to the bus but communicates via the DICE, one of the control modules connected to the I-bus, and so has access to all control modules connected to the bus.

The data transfer rate of the P-bus is ten 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 sent out by a control module is available to all other control modules connected to the bus. The MIU ensures that the information which is available on one bus is also made available on the other.

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 two leads, bus+ (green cable) and bus- (white cable). The leads are twisted to reduce susceptibility to electrical disturbances.

TWICE uses the following information

Information	Values	From	The value depends on the following sensor input, signal or function
Vehicle speed	km/h, mph	MIU	Rear left wheel speed (lead from ABS). TWICE uses the information for the central locking system's automatic control of locking.
Identification number		MIU	The value is created in the MIU when the immobilizer code is programmed in the TWICE.
SID button	Night Panel	SID	Button. TWICE uses the information for disconnecting the glass breakage sensor and tilt sensor. The Night Panel button is used for this purpose when the key has been removed from the ignition switch.
Ignition +B	ON/OFF	DICE	Ignition switch.
Ignition +15	ON/OFF	DICE	Ignition switch.
Ignition +50	ON/OFF	DICE	+15 present but not +54.
Ignition +54	ON/OFF	DICE	Ignition switch. TWICE uses the information to inform the lamp check, seat belt warning, electrically heated rear seat and electrically adjustable front seat functions of the ignition switch status.
Outside temperature	°C	SID	Outside temperature sensor, control module adjustment. TWICE uses the information to control the electric heating in the rear seat.
Wheel speed RL	0-300 km/h	TC/ABS	Speed sensor, rear left.
Diagnostic communication		Tech 2	See Bus and diagnostics communication

TWICE sends out the following information

Information	Values	Used by	The value depends on the following sensor input, signal or function
Left rear light faulty	YES/NO	SID	Control module current measurement of the output to the lamps. The SID uses the information to display CHECK messages.
Right rear light faulty	YES/NO	SID	Control module current measurement of the output to the lamps. The SID uses the information to display CHECK messages.
Left rear light	ON/OFF	DICE	The control module is energized from the light switch. DICE uses the information to calculate the position of the light switch.
Right rear light	ON/OFF	DICE	The control module is energized from the light switch. DICE uses the information to calculate the position of the light switch.
Left brake light faulty	YES/NO	SID	Control module current measurement of the output to the lamp. The SID uses the information to display CHECK messages.
Right brake light faulty	YES/NO	SID	Control module current measurement of the output to the lamp. The SID uses the information to display CHECK messages.
High level brake light faulty	YES/NO	SID	Control module current measurement of the output to the lamp. The SID uses the information to display CHECK messages.
Brake lights	ON/OFF	TCM, SID	Brake light switch. TCM uses the information for engaging gear. Trionic uses the information for the cruise control function.
Passenger seat occupied	YES/NO	ACC	Seat sensor. ACC uses the function for one or two zone control.
Sound	Sound information	SID	On text message. SID uses the information to generate an acoustic signal for the seat belt warning.
Driver's door	OPEN/CLOSED	MIU, DMM, PSM, DICE	Door switch. DICE uses the information to turn on the interior light. MIU uses the information to turn on the display for open door. PSM uses the information to control the function, electric powered front seat.
Passenger door	OPEN/CLOSED	MIU, DMM, PSM, DICE	Door switch. DICE uses the information to turn on the interior light. MIU uses the information to turn on the display for open door. PSM uses the information to control the function, electric powered front seat.
Left rear door	OPEN/CLOSED	MIU, DICE	Door switch. DICE uses the information to turn on the interior light. MIU uses the information to turn on the display for open door.
Right rear door	OPEN/CLOSED	MIU, DICE	Door switch. DICE uses the information to turn on the interior light. MIU uses the information to turn on the display for open door.
Boot lid	OPEN/CLOSED	MIU, DICE	Door switch. DICE uses the information to turn on the luggage compartment light. MIU uses the information to turn on the display for open tailgate.
Test brake lights	ON/OFF	SID	Control module programming and brake light switch. The SID provides information to the driver via a CHECK message to press the brake pedal.
Horn	0: 6: 42 ms	SID	Anti-theft alarm function and central locking function. The SID uses the information to activate the horn relay when the car is TSL locked.
Hazard flashers	ON/OFF	DICE	Anti-theft alarm function and central locking function. DICE uses the information to activate the hazard flashers when the alarm is tripped.
Text message		SID	Anti-theft alarm function and central locking function. The SID uses the information to display text messages for TWICE functions.
Steering wheel position	LHD/RHD	PSM, ACC, MIU	PSM uses the information to know which door is the driver's door. ACC uses the information to know which is the driver's zone.
Key correct	ON/OFF	Audio	Immobilizer function. Audio uses the information for theft protection.
Immobilization	ON/OFF	Trionic	Immobilizer function. Trionic uses the information to allow the engine to be started.
Central locking system	LOCKED/UNLOCKED	DICE	DICE uses the information to turn on the interior light when the car is unlocked.
Body type	4D/5D	SPA	Control module programming.
Diagnostics	Response to query from diagnostic tool	DICE/Diagnostic tool	The control module must be energized and the bus leads intact. See Bus and diagnostics communication