Bus communication

Bus communication

•	Control module, ACC (216)

•	Radio connector C (267c)

•	Control module, Airbag/SRS (331)

•	Radio (353)

•	CD changer (355)

•	Control module, PSM (357Dk)

•	MIU (540c)

•

SID (541)

•	Control module, ABS (547)

•	Control module, STC (565)

•	Control module, EDC 15 (595)

•	Control module, auxiliary heater (597)

•	Diesel pump (598)

•	Control module, DICE (628)

•	Control module, TWICE (632)

P-bus and I-bus

A "bus" in this context means cables through which information is sent digitally and serially. By digital is meant that the voltage difference between the cables has only two values, approx. 0 and 5 V. The information is coded so that different combinations of pulses with the values 0 and 5 V denote different things.

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

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

Only diesel cars and petrol cars with Trionic T7 have a P-bus. The other petrol engine variants have engine management systems and automatic transmission from the previous 900 models (T5, M2.10.3 and TCM), which are not bus-connected.

As in the 9-5, the Airbag and ABS control modules are not bus-connected.

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 on the P-bus is ten times faster than on the I-bus. This is because the power train systems require information with as short a delay as possible.



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 information is transferred between control modules via two leads, bus+ (green lead) and bus- (white lead). The leads are twisted to reduce their sensitivity to electrical interference.

The MIU uses the following information:

Information	Values	From	The value depends on the following sensor input, signal or function
LH direction indicators	ON/OFF	DICE	MIU turns on the indicator lamp for the LH direction indicators.
RH direction indicators	ON/OFF	DICE	MIU turns on the indicator lamp for the RH direction indicators.
Rear fog light	ON/OFF	DICE	MIU turns on the indicator lamp for the rear fog lights.
Driver's door	OPEN/CLOSED	TWICE	Door switch. The MIU lights the symbol for the driver's door.
Passenger door	OPEN/CLOSED	TWICE	Door switch. The MIU lights the symbol for the passenger's door.
LH rear door	OPEN/CLOSED	TWICE	Door switch. The MIU lights the symbol for the left rear door.
RH rear door	OPEN/CLOSED	TWICE	Door switch. The MIU lights the symbol for the right rear door.
Tailgate	OPEN/CLOSED	TWICE	Tailgate switch. The MIU lights the symbol for the tailgate.
Steering wheel location	LHD/RHD	TWICE	MIU turns on the indicator for the driver/passenger door
Info Disp Lamp	ON/OFF	SID	Text message. The MIU lights the Info Display indicator lamp.
Rheostat level	0-100 %	SID	Rheostat control module input. The main instrument unit controls the instrument lighting.
Rheostat Night Panel	0-100 %	SID	Rheostat control module input reduced internally by a fixed value.
Night Panel	ON/OFF	SID	Button. The MIU turns off certain instrument and display lighting.
Display lighting	0-100 %	SID	Rheostat control module input. The MIU uses this information to control the display lighting.
Light intensity in compartment	Lux	SID	Light sensor. The MIU uses this value to control the intensity of the indicator lamps.
CHECK ENGINE lamp	ON/OFF	EDC 15	Internal diagnostics. The MIU turns on the CHECK ENGINE lamp.
CRUISE Lamp	ON/OFF	EDC 15	Cruise control function. The MIU turns on the CRUISE lamp.
Fuel consumed since start	0-65535 ml	EDC 15	Fuel injection function. Used by the SID for the trip computer functions, can be adjusted by an offset on MIU.
Engine speed	0-6000 rpm	EDC 15	Crankshaft sensor. The MIU controls the tachometer.
Coolant temperature	-40-215ºC	EDC 15	Coolant temperature sensor. The MIU controls the coolant temperature gauge.
Glow indicator lamp	ON/OFF	EDC 15	Glow function. The glow indicator lamp lights during pre-heating.

The MIU sends the following information:

Information	Values	Used by	The value depends on the following sensor input, signal or function
Vehicle speed	km/h (mph)	EDC 15, DICE, SID, ACC, Audio, TWICE, STC	The main instrument unit calculates the current vehicle speed based on information on the wheel speed from the ABS control module.
Sound	Sound information	SID	Request for acoustical signal when central warning lamp or Info Displ goes on.
Fuel level	litres	SID	MIU sends information on the current fuel volume in the tank.
Odometer reading	km, miles	SID	Information on the driven distance.
Identification number	---	TWICE	Immobilizer function
Fuel consumed since start	ON/OFF	0-65535 ml	Bus from EDC15. The value is corrected with an adjustment factor in the MIU. The factor can be adjusted with the diagnostic tool.
STOP FOR FUEL	ON/OFF	SID	When the fuel level falls below 3 litres ON is sent. The MIU sends a text message to the SID, which shows it on the display.
Diagnostics communication	---	DICE/ Diagnostic tool	DICE/diagnostic tool.