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 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 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 the information sent from one control module is accessible for all other control modules on the bus. The MIU is responsible for ensuring that information available on one bus is also available on the other 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 two leads, bus+ (green lead) and bus- (white lead). The leads are twisted to reduce susceptibility to electrical interference.

DICE uses the following information

Information	Values	From	The value depends on the following sensor input, signal or function
LH rear light	ON/OFF	TWICE	The control module input is supplied with current from the light switch. DICE uses the information for the instrument lighting.
RH rear light	ON/OFF	TWICE	The control module input is supplied with current from the light switch. DICE uses the information for the instrument lighting.
Driver's door	OPEN/CLOSED	TWICE	Door switch. DICE uses the information to turn on/off the interior lighting.
Passenger door	OPEN/CLOSED	TWICE	Door switch. DICE uses the information to turn on/off the interior lighting.
Passenger door, rear LH	OPEN/CLOSED	TWICE	Door switch. DICE uses the information to turn on/off the interior lighting.
Passenger door, rear RH	OPEN/CLOSED	TWICE	Door switch. DICE uses the information to turn on/off the interior lighting.
Boot lid/tailgate	OPEN/CLOSED	TWICE	Door switch. DICE uses the information to turn on/off the luggage compartment lighting.
Hazard flashers	ON/OFF	TWICE	Anti-theft alarm function and central locking function. DICE uses the information to activate/deactivate the hazard flashers for the car's anti-theft alarm.
A/C	ON/OFF	ACC	AUTO selected and outside temperature (bus from SID). DICE uses the information to turn on/off the car's A/C function.
Electrically heated rear window	ON/OFF	ACC	Button on dashboard. DICE uses the information to turn on/off the electrical heater.
Vehicle speed	km/h	MIU	Wheel speed, rear left (cable from ABS). DICE uses the information for the intermittent wiper function and for the car's radiator fan system.
Rheostat level	0-100%	SID	Rheostat control module input. DICE uses the information to control the brightness of the instrument and control lighting.
Rheostat Night Panel	0-100%	SID	Rheostat control module input, reduced by a fixed value. DICE uses the information to control the brightness of button illumination when NIGHT PANEL is active.
Night Panel	ON/OFF	SID	Button. DICE uses the information on whether NIGHT PANEL is activated or deactivated.
Display lighting	0-100%	SID	Rheostat control module input or light sensor. DICE uses the information to control the brightness of the display.
Outdoor temperature	°C	SID	Outside temperature sensor, control module adjustment. DICE uses the information to control the radiator fan and A/C.
Engine Running	ON/OFF	Trionic	Crankshaft sensor. DICE uses the information to control the radiator fans.
Coolant temperature	-40-215°C	Trionic	Engine coolant temperature sensor. DICE uses the information to control the radiator fan and A/C systems.
Wheel speed RL	0-300 km/h	TC/ABS	RL wheel speed sensor
Diagnostics		Tech 2	See Bus and diagnostics communication

DICE sends the following information

Information	Values	Used by	The value depends on the following sensor input, signal or function
A/C	ON/OFF	Trionic	A/C (bus from ACC), coolant temperature (bus from Trionic), A/C pressure and evaporator temperature. Trionic uses the information to control relays.
A/C pressure	0-30 bar	Trionic	A/C pressure sensor. Trionic uses the information for load compensation.
Current consumption	0-255 A	Trionic	Activation by the control module of the relay outputs for the radiator fans and electrically heated rear window. Trionic uses the information for load compensation.
Idling speed increase	ON/OFF	Trionic	High radiator fan speed activated once while driving. Trionic uses the information to detect “warm market”.
Reverse gear	ON/OFF	PMM, Trionic, SPA	Reversing light switch. PMM uses the information to adjust the rear-view mirrors.
Position lights	ON/OFF	MIU, SID	Rear light RH and LH (bus value from TWICE). MIU uses the information to turn on/off the position light indicator on the main instrument panel.
Rear fog light	ON/OFF	MIU	Activation by the control module of the output to the fog light. MIU uses the information to turn on/off the rear fog light indicator on the main instrument panel.
LH direction indicators	ON/OFF	MIU, SID	Activation by the control module of the output to the lamps. MIU uses the information to indicate activated LH direction indicators with control lamp on main instrument panel. SID uses the information for acoustic indication of activated direction indicators “tick-tack”.
RH direction indicators	ON/OFF	MIU, SID	Activation by the control module of the output to the lamps. MIU uses the information to indicate activated RH direction indicators with control lamp on main instrument panel. SID uses the information for acoustic indication of activated direction indicators “tick-tack”.
Rear fog light broken	YES/NO	SID	Control module current measurement of the output to the fog lamp. SID uses the information to display CHECK messages.
Sound	Sound information	SID	Control module programming and seat belt switch, and driver's/passenger door open (bus from TWICE). SID uses the information to generate an acoustic warning.
Electrically heated rear window	ON/OFF	ACC	Control module activation of relay output to rear window heater. ACC uses the information to confirm that the rear window heating is active.
VIN	Chassis number	Audio	Control module programming. Audio uses the information for the system's anti-theft protection.
Ignition +B	ON/OFF	Audio, TWICE	Ignition switch. Informs Audio and TWICE of the position of the ignition switch.
Ignition +15	ON/OFF	TWICE	Ignition switch. Informs TWICE of the position of the ignition switch.
Ignition +54	ON/OFF	TWICE	Ignition switch. Informs TWICE of the position of the ignition switch.
Ignition +50	ON/OFF	TWICE, ACC	Ignition switch. Informs TWICE of the position of the ignition switch.
Diagnostics		Tech 2	See Bus and diagnostics communication