Computers and Control Systems: Description and Operation
GF07.61-P-2005MCU ME-SFI Driving Mode, Function
1 Status of the accelerator pedal
2 Intake manifold pressure
3 Intake air temperature
4 Knock sensor signal
5 Coolant temperature
6 tank pressure sensor signal
7 Oil pressure
8 Engine speed and top dead center of cylinder 1
9 Position of the camshaft
10 Residual oxygen content in the exhaust upstream/downstream of the catalytic converter
11 Actuation of air injection pump
12 Heating O2 sensors
13 Actuation of fuel injection valves
14 Ignition coils actuation
15 Actuation of throttle valve actuator
16 Position feedback from the throttle valve actuator
17 Actuation of the tank vent valve
18 Actuation of the adjustable camshaft timing solenoid
19 Request for coolant fan motor
20 Actuation of the coolant fan motor
21 Fuel pump actuation
22 Shift command
23 Status of the engaged gear range/ shift operation
24 Crash signal
25 ESP status
26 Request for refrigerant compressor (for code (I01) Air conditioning Plus)
27 Actuation of the refrigerant compressor (for code (I01) Air conditioning Plus)
28 Request for indicator and warning lamps
29 Fill level for the fuel tank
30 Actuation of the secondary air injection pump switchover valve
31 Actuation of the outside air shutoff valve
A1 Instrument cluster
A9 Refrigerant compressor (for code (I01) Air conditioning Plus)
A16 Knock sensor
B4/3 Fuel tank pressure sensor
B6/1 Camshaft Hall sensor
B11/4 Coolant temperature sensor
B28 Intake manifold pressure sensor
B37 Accelerator pedal sensor
G3/1 O2 sensor downstream from catalytic converter
G3/2 O2 sensor upstream TWC
K64 Secondary air injection pump relay
L5 Crankshaft position sensor
M3/3 Fuel pump with fuel tank sensor
M3/3b1 Fuel tank sensor
M4/2 Coolant fan motor
M16/6 Throttle valve actuator
M33 Secondary air injection pump
N2/7 Restraint systems control unit
N3/10 ME-SFI [ME] control unit
N10/10 SAM control unit
N15/6 Automated manual transmission control unit
N23 Heater/air conditioning operating unit (for code (I01) Air conditioning Plus)
N47-5 ESP control unit
S41/1 Oil pressure switch
T1/1 Cylinder 1 ignition coil
T1/2 Cylinder 2 ignition coil
T1/3 Cylinder 3 ignition coil
Y32 Secondary air injection pump switchover valve
Y49 Adjustable camshaft timing solenoid
Y50 Outside air shutoff valve
Y58 Fuel tank vent valve
Y62/1 Cylinder 1 fuel injection valve
Y62/2 Cylinder 2 fuel injection valve
Y62/3 Cylinder 3 fuel injection valve
CAN Controller Area Network (data bus/ CAN bus) (CAN)
The driving mode includes the following subfunctions:
^ Idle speed control:
The ME-SFI [ME] control unit regulates a stable idle speed under all operating conditions.
^ Warm-up control:
The engine is brought rapidly up to operating temperature.
^ Acceleration enrichment
Dynamic enrichment prevents jerking when accelerating.
^ Overrun fuel shutoff
The braking effect of the engine is increased in overrun mode and fuel consumption reduced
^ Antiknock control:
The antiknock control guarantees knock-free operation of the engine with various fuel qualities and under all operating conditions.
^ Camshaft adjustment
Camshaft adjustment lowers emissions and increases performance
^ Fan control
The fan motor is actuated to reduce the coolant temperature
^ Maximum engine speed limitation
For protection of the engine and the drive train the engine speed is limited
^ External quantity intervention
The injection quantity is adapted to various driving modes.
^ O2 sensor heater:
The O2 sensor heater is used to bring the O2 sensors rapidly up to operating temperature.
^ Two-sensor control
The effect of the catalytic converter is monitored by the signals from the O2 sensor upstream of CAT and by the signals from the O2 sensor downstream of CAT
^ Fuel regeneration:
Fuel vapors are fed to the engine. Moreover, fuel vapors are not allowed to escape into the atmosphere.
^ Checking for leaks in the tank:
Gross, fine and very fine leaks are checked by measuring the pressure in the tank.
^ Safety fuel shutoff
In the event of a crash, the fuel pump is shut off and the fuel injection valves are actuated briefly
^ Catalytic converter heating
The catalytic converter is brought rapidly to the operating temperature
^ Secondary air injection:
In addition, fresh air is let into the exhaust flow to improve the exhaust emission values.
^ Ignition system:
A static high-voltage distribution with 3 single-spark ignition coils is used.
Idle speed control
The throttle valve actuator controls the idle speed by altering the position of the throttle valve. Actuation is by the ME-SFI [ME] control unit.
The ME-SFI [ME] control unit regulates the idle speed according to the input signals for different engine loads (e.g. a switched on refrigerant compressor).
The ME-SFI [ME] control unit evaluates signals from the following components for idle speed control:
^ Camshaft Hall sensor
^ Coolant temperature sensor
^ Intake manifold pressure sensor
^ Accelerator pedal sensor
^ Crankshaft position sensor
^ Throttle valve actuator
Warming-up control
After the start process the fuel-air mixture is further enriched via the warm-up control.
The warm-up control compensates for the fuel unavailable for combustion due to precipitation on the cold inner walls of the intake manifold.
The engine is assigned an additional fuel quantity by the ME-SFI [ME] control unit according to a performance map. To do this, the actuation period of the fuel injection valves is extended accordingly.
Warm-up control is dependent on:
^ Coolant temperature
^ Engine speed
^ Engine load
Acceleration enrichment
The opening of the throttle valve is dependent on the accelerator pedal sensor.
For rapid opening of the throttle valve the mixture goes lean for a short time.
Therefore a short-term mixture adaptation takes place in that the ME-SFI [ME] control unit assigns the engine an additional fuel quantity.
Acceleration enrichment is dependent on:
^ Coolant temperature
^ Accelerator pedal position
^ Engine speed
^ Engine load
Inertia fuel shutoff
The braking effect of the engine in the overrun mode is increased and the fuel consumption is reduced by means of the overrun fuel shutoff.
In overrun mode, the ME-SFI [ME] control unit switches off the fuel injection valves depending on the temperature and the speed. The fuel injectors are operated again, when the accelerator pedal is depressed or when idle speed is reached, and no further overrun mode exists.
Anti-knock control [AKC]
The antiknock control ensures knock-free operation of the engine at all engine speeds, for all fuel grades and under all operating conditions. To do this for uncontrolled combustion (knocking) the ignition timing is set to "retard".
If knocking continues to occur, the ignition timing (depending on engine speed) continues to be retarded in stages until maximum retardation is achieved.
If knock-free combustion is restored, the retardation is reduced in stages after a few ignitions (depending on engine speed) until the normal performance map value is achieved or knocking once again occurs.
Input signals for anti-knock control
^ Knock sensor
^ Camshaft Hall sensor
^ Coolant temperature sensor
^ Accelerator pedal sensor
^ Crankshaft position sensor
Camshaft adjustment
The adjustment of the camshaft takes place electrohydraulically via the camshaft timing solenoid and the camshaft adjuster. Here a control plunger in the adjustable camshaft timing solenoid ensures that the applied engine oil pressure is passed through to the respective connection on the camshaft adjuster.
The intake camshaft can now be adjusted by turning the adjuster to "advanced" (large valve overlap) or "retarded" (small valve overlap).
The adjustment time is dependent on the engine oil pressure at the adjuster, oil viscosity and oil temperature.
Camshaft adjustment is used to reduce pollutants in the exhaust gas and to increase the performance of the engine.
In the case of failure of the camshaft Hall sensor, camshaft adjustment is disabled.
Fan control
The ME-SFI [ME] control unit decides according to a performance map about switching on the coolant fan motor. Depending on the coolant temperature and operation of the air conditioning system, the fan motor is switched on. Actuation takes place via the SAM control unit.
Maximum engine speed limitation
The ME-SFI [ME] control unit detects the engine speed via the crankshaft position sensor signal. This is limited to protect the engine and the drive train through retarding the ignition timing and cutting out the fuel injection valves.
The ME-SFI [ME] control unit also asks for the current gear range from the automated manual transmission control unit in order, if necessary,to initiate an upshift. If the throttle valve actuator is defective or signals implausible, the engine speed is also limited.
External intervention in the fuel quantity
With external quantity intervention, the engine torque is reduced (e.g. for an ESP regulation) by the ME-SFI [ME] control unit. A reduction of the engine torque takes place through reduction of the injection quantity.
The ME-SFI [ME] control unit receives appropriate signals for this via the CAN from:
^ Automated manual transmission control unit
- Shift process
^ ESP control unit
- ESP regulation
O2 sensor heater
The O2 sensor downstream of TWC and the O2 sensor upstream of TWC only allow lambda regulation above an operating temperature of about 300°C. In order to reach this temperature as quickly as possible the O2 sensors are fitted with an integral heater. The O2 sensor heater is actuated by the ME-SFI [ME] control unit. Rapid heating of the sensors means a high degree of control is achieved, even at low exhaust temperatures.
Two-sensor control
The ME control unit uses the signal from the O2 sensor downstream TWC and the O2 sensor upstream TWC to determine the mean Lambda value. This value is compared with a stored value for optimum exhaust emissions.
If the deviation is too large after a number of measurements, a correction variable is determined for the lambda control.
Using the correction variable aging of the O2 sensor upstream of TWC is compensated for within certain limits. If the correction variable exceeds the limit value, a new O2 sensor upstream of TWC must be installed.
The correction values are map-controlled and are implemented by the ME control unit by adapting the fuel injection. If the limits are exceeded or if the plausibility check of the signal from the O2 sensor downstream of TWC and O2 sensor upstream of TWC is negative, the CHECK ENGINE indicator lamp (A1e26) in the instrument cluster lights up .
The O2 sensor signal downstream of TWC [KAT] and O2 sensor signal upstream of TWC [KAT] is also used to monitor the effect of the catalytic converter.
Fuel regeneration
The evaporative emission control system prevents fuel vapors escaping to atmosphere. The fuel vapors are stored in the activated charcoal filter and then sent later to the engine for combustion.
The fuel vapors from the fuel tank flow through the purge line and are stored in the activated charcoal filter. In driving mode the tank vent valve opens and the fuel vapors are led to combustion. For a cold engine or a lower air mass (e.g. neutral) the tank vent valve is closed by the ME-SFI [ME] control unit and the combustion of fuel vapors interrupted. This leads to better running characteristics of the engine in partial load operation.
The ME-SFI [ME] control unit requires the following information for actuation of the tank vent valve:
^ Coolant temperature
^ Intake manifold pressure
Fuel tank leak test
Test requirements
^ Engine at idle
^ Vehicle stationary
^ Intake air temperature <45°C
^ Coolant temperature for engine start <100°C
^ Drive position "D" or "R" is engaged
^ Fuel level in the fuel tank between approximately 1/4 and 3/4
The fuel system is tested for leaks in three stages (function chain). The leak test detects leaks with a diameter of 0.5 mm and more:
^ Test for gross leaks (equal to or greater than 3 mm)
^ Test for fine leaks (equal to or greater than 1 mm)
^ Test for very fine leaks (equal to or greater than 0.5 mm)
Test for gross leak:
The outside air shutoff valve is closed and the tank vent valve is opened. Intake manifold vacuum present in fuel tank. This vacuum is measured by the tank pressure sensor.
If no vacuum is formed in the fuel tank, there is a larger leakage (for example, open tank cap, loose hose line). The test is interrupted and the fault 'gross leak' is registered.
Test for fine leak:
The tank vent valve is closed at a vacuum of around -6 mbar. The system is closed and thereby airproof. The vacuum is them measured for approx. 30 seconds. The vacuum must not reduce more rapidly than 0.3 to 0.5 mbar per second (depends on fuel level). If the vacuum drops more rapidly, there is a fine leak. The test is interrupted and the fault 'fine leak' is registered.
Test for very fine leak:
If no minor leak has been detected, the purge system is briefly enabled and a vacuum of approx. -6 mbar is built up again. The vacuum must not drop any faster than 0.1 to 0.15 mbar per second for a closed system (depending on the level of fuel in the tank). If the vacuum drops more rapidly, the fault 'very fine leak' is registered.
The outside air shutoff valve is opened again after the tests.
If a gross, fine or a very fine leak is detected, the CHECK ENGINE indicator lamp is actuated by the ME-SFI [ME] control unit via the CAN.
Safety fuel shutoff
If the ME-SFI [ME] control unit receives a crash signal from the restraint systems control unit via the CAN, it switches off the fuel pump with fuel level sensor and actuates the fuel injection valves for a short time to make the fuel system become unpressurized.
Catalytic converter heating
The catalytic convertor heater rapidly brings the catalytic convertor to the operating temperature In this way the exhaust gas emissions after a cold start are strongly reduced. Controlling of the catalytic converter heating is by the ME-SFI [ME] control unit.
The ignition timing is adjusted to 'retarded' in the neutral depending on the coolant temperature in order to increase the exhaust temperature. By delaying the ignition timing point and the resultant combustion in the exhaust tract, the catalytic converter is heated rapidly.
The idle speed is adjusted in line with the coolant temperature.
Secondary air injection
Function requirement
^ Coolant temperature between 7°C and 36°C
The secondary air injection causes after burning of the unburnt hydrocarbons on the exhaust side. As a result, the catalytic converter reaches its operating temperature more quickly after the cold start and the emissions in the exhaust are reduced.
The secondary air is provided by the secondary air injection pump, which is actuated by the ME-SFI [ME] control unit via the secondary air injection relay for t = 33 s. The secondary air injection pump switchover valve actuates the secondary air valve via a vacuum, which enables air supply into the exhaust manifold. The secondary air injection pump switchover valve is also actuated by the ME-SFI [ME] control unit.
The actuation is aborted by the ME-SFI [ME] control unit at an engine speed of more than 4000 rpm. If the engine speed then falls below 4000 rpm, the secondary air injection is restarted.
Ignition system
Three single-spark ignition coils are used at the spark plugs (R4). Actuation of ignition coils takes place over the ME-SFI [ME] control unit.
Static high-voltage is distributed directly to the spark plugs without an ignition distributor.
Advantages of the rotorless high voltage distribution are:
^ significantly lower electromagnetic interference level (no naked sparks)
^ No rotating parts (no wear)
^ Noise reduction
^ No need for ignition lines
The ME-SFI [ME] control unit evaluates signals from the following components for actuation of the ignition coils:
^ Knock sensor
^ Camshaft Hall sensor
^ Coolant temperature sensor
^ Intake manifold pressure sensor
^ Accelerator pedal sensor
^ Crankshaft position sensor
^ Throttle valve actuator
