System Overview, Trionic T7

System Overview, Trionic T7

System Overview, Trionic T7:

- Main Instrument Unit (540d)
- Engine oil pressure sensor (44)
- Switch, handbrake (43)
- Generator (2)
- Level switch, brake fluid (42)
- Level sensor, fuel (46)
- Control module, ABS (547)
- SRS/Airbag (331)
- Diagnostics (445)

Main Components, Trionic T7

Main Components, Trionic T7:

Brief Description Of The Main Instrument, Trionic T7

General
The main instrument unit conveys information to the driver and functions as an information link between the P bus and the I bus.

The main instrument unit has its own diagnostics function and sets a diagnostic trouble code when a fault occurs.

The main instrument unit incorporates the following functions:
- Control module
- Speedometer
- Odometer/trip meter
- Tachometer
- Fuel gauge
- Coolant temperature gauge
- Turbo pressure gauge (cars with turbo)
- Instrument and display lighting
- Warning and indicator lamps

Control module
The main instrument unit's control module receives information from other systems as well as from its own sensors. It processes the information and uses it to control instruments and lamps. Some information is send out on the bus.

Speedometer
The car is equipped with an electronic speedometer which shows the current speed. The left rear wheel sensor sends speed information to the ABS control module which processes it and sends it on to the main instrument unit.

Odometer/trip meter
The main instrument unit's control module stores the distance covered and shows the mileage on the odometer display. The odometer display has a six-digit counter which the control unit continuously updates from 000000 to 999999 km (or miles). The trip meter has a four-digit counter which starts at 000.0 and goes up to 999.9 km (or miles).

Tachometer
The tachometer is electronic and shows the current engine rpm. It receives engine speed information continuously from Trionic T7 via the bus. Engine speed indication below 1100 rpm is damped to ensure a steadier reading.

Fuel gauge
The fuel gauge gives the driver information on how much fuel is left in the tank. It consists of a fuel gauge in the main instrument unit and a level sensor in the tank.

When the fuel remaining in the tank is less than 10 litres, the main instrument units control module switches to measuring fuel consumption. The information comes from Trionic T7 via the bus. This gives a more accurate reading of the fuel level. The Fuel Reserve indicator lamp comes on when the amount of fuel remaining is less than 10 litres.

Low fuel level (OBDII)
This function is used only for OBDII diagnostics.

Tank venting diagnostics (OBDII)
The Trionic sends information on the bus to the main instrument unit on the diagnostic status of the tank venting system. If there is leakage in the venting system, the main instrument unit sends the information "Tighten fuel filler cap ON" via the bus. The SID unit then displays the requested message.

Coolant temperature gauge
The coolant temperature gauge gives the driver information on engine coolant temperature. The information is obtained from Trionic T7 on the bus.

Turbo pressure gauge
The car has an electronic turbo pressure gauge which shows the current turbo pressure. Information on the pressure in the intake manifold comes on the bus from Trionic T7. The main instrument unit controls the turbo pressure gauge so that its reading is proportional to the pressure in the intake manifold.

Warning and indicator lamps
The main instrument unit contains the following lamps:
- Indicator lamp INFO DISPLAY, lights up when a message is shown on the SID unit.
- Central warning lamp, lights up when a fault occurs in a system having to do with the car's safety.
- Oil pressure warning lamp, warns the driver when engine oil pressure is too low.
- Charge warning lamp, indicates to the driver whether or not the generator is charging.
- AIRBAG warning lamp, warns the driver when a fault has occurred in the airbag system.
- Brake fluid warning lamp, warns the driver when the fluid level in the reservoir is too low and when a fault has occurred in the anti-lock brake system (ABS).
- Handbrake warning lamp, informs the driver that the handbrake is applied.
- ABS warning lamp, the lamp lights up when there is a fault in the ABS system.
- Fuel reserve indicator lamp, the lamp lights up when the fuel level is below 10 litres.
- CHECK ENGINE indicator lamp, warns the driver that there is a fault in the engine management system.
- Direction indicator repeater lamps, right and left. Show when the direction indicators are on.
- CRUISE indicator lamp, on cars with cruise control the lamp lights up when cruise control is engaged.
- SHIFT UP indicator lamp, the lamp lights up when a higher gear should be engaged (certain markets).
- Lights-on indicator lamp, indicates that the headlamps are on.
- Rear fog light indicator lamp, indicates that the rear fog light is on.
- Main beam indicator lamp, indicates that the main beam is on.
- Door indication, indicates if any of the doors or the tailgate is open.

Instrument and display lighting
The main instrument unit's control module controls the instrument and display lighting according to the light intensity in the cabin in combination with the selected rheostat setting. This gives a good level of lighting for day or night driving and optimum bulb life.

P bus and I bus

P Bus And I Bus:

P bus and I bus in the Saab 9-3
On the Saab 9-3, not as many control modules as on the Saab 9-5 are connected to a bus system.

However, the Trionic T7 is not connected to the I bus. This system requires much faster communication so that there are no noticeable delays, as when the Trionic T7 requests a certain fuel mass for injection.

Therefore, the Trionic T7 is connected to a separate bus called the P bus (Powertrain Bus). Communication on the P bus is ten times faster than on the I bus.

In addition, the P bus is connected to the MIU. The MIU ensures that information which is available on one bus is also available on the other.