Control of fuel injection system
The ME control unit actuates according to the input signals and the retracted performance maps in the ME control unit, the fuel injection valves separately, corresponding to the firing order (sequential). The ME-SFI control unit calculates the opening times (injection times) of the fuel injectors.
Control of ignition system
The ME control unit actuates according to the input signals and the retracted performance maps in the ME control unit,
the ignition coils or the ignition system ECI. The ME-SFI control unit calculates the ignition angle values and controls the anti-knock control (AKC).
Control of idle speed control
The ME-SFI control unit operates the EA/CC/ISC actuator (throttle valve actuator) in line with the input signals and the maps stored in the ME-SFI control unit.
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Control of cruise control
The ME-SFI control unit operates the EA/CC/ISC actuator (throttle valve actuator) for the cruise control function in line with the input signals and the position of the cruise control switch.
Additional cruise control functions are the variable vehicle speed limiter and the individually programmable permanent maximum speed and Distronic.
Diagnosis/DTC memory
The ME-SFI control unit checks its inputs and outputs for plausibility and recognizes possible faults. The following faults can be distinguished:
- Faults constantly present Loose contact faults that occurred during a drive.
The faults are erased in the ME-SFI control unit after circuit 30 is interrupted.
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Drive authorization system/immobilizer
The ME-SFI control unit is always equipped with an immobilizer. When the vehicle is locked, the drive authorization system control unit transmits information over the CAN databus to the ME-SFI control unit, which thereupon interlocks the engine management system (fuel injection system). The engine can be started (start enable) only once the vehicle is again unlocked with the authorized key and the drive authorization system control unit transmits a message to this effect over the CAN databus to the ME-SFI control unit.
Engine speed signal
The ME-SFI control unit generates the short-circuit proof engine speed signal TNA from the signals supplied by the crankshaft position sensor, and outputs it to other control units as follows:
Square-wave signal with constant on/off ratio, maximum current approx. 20 mA.
Engine 111: 2 pulses/engine revolution
Engine 104, 112, 137: 3 pulses/engine revolution
Engine 119, 113: 4 pulses/engine revolution
Engine 113 with ME 2.8: 3 pulses/engine revolution
Engine 120: 3 pulses/engine revolution
(from right ME-SFI control unit)
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Actuations with HHT or STAR DIAGNOSIS
Functions can be actuated specifically for diagnostic purposes. These are listed in a menu point.
Version coding
For adapting the ME-SFI control unit to different vehicle versions and vehicle equipment by means of matching code numbers. Coding is performed with the Hand-Held Tester (HHT) or with STAR DIAGNOSIS. The following vehicle versions and equipment versions can be coded using the version coding:
Vehicle model
National version
with or without TWC.
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Fuel consumption signal
The fuel consumption signal (e.g. 8 l/hour) is calculated from the injection times and the current fuel consumption is advised to the trip computer by means of square-wave pulse packages.
One square-wave pulse means 0.2 l/hour.
With CAN compatible instrument cluster: Information is transmitted via CAN from the ME control unit to the instrument cluster.
Delayed-off running
After the ignition is switched off, the ME-SFI control unit performs a delayed-off run during which certain data memories are updated (e.g. the DTC memory). The duration is dependent on the coolant temperature (at 80 °C approx. 4 s, at
20 °C approx. 60 s and at -30 °C approx. 150 s) and whether the engine was started after ignition ON. If the ignition is switched off without starting the engine, the run-on time is always approx. 4 s.
Engine 112.946 with code 929 Flexible Fuel Vehicle (FFV)
The engine control unit hasfor FFV additional functions, as identifying Ethanol portion after each fueling and adapting the mixture correspondingly