ME-SFI [ME] control unit, component description

P07.70-2098-01

N3/10 ME control unit

Location

The MED 9.7 control unit is located on the intake manifold supporting the engine.



The abbreviated designation MES 9.7 means:

M = Motronic (motor electronics)

E = Electronic accelerator pedal (electronic accelerator)

D = Direct injection

9.7 = Version

P07.70-2137-01

N3/10 ME control unit

1 Clutch on the vehicle side

2 Clutch on the engine side

Task

The ME control unit controls the functions appropriately according to input signals:

 Injection system in the operating mode homogeneous or stratified charge operation

 Ignition system

 Electronic accelerator/idle speed control

 Diagnosis/fault storage

 Drive authorization system/immobilizer

-----------------------------------------------------------------------------------------

Design

Connection is achieved on the engine-side and on-board via two couplings interlocked via slide valves. The ME control unit is attached to the coolant circuit (low-temperature cooling system) for cooling. Vibrations are suppressed by rubber brackets.

-----------------------------------------------------------------------------------------

Function

Control of fuel injection system

The ME control unit actuates the fuel injectors separately corresponding to the firing order (sequentially) according to the input signals and performance maps stored in the ME control unit. The ME-SFI control unit calculates opening times (injection times) of fuel injectors.

Control of idle speed control

The throttle valve actuator is actuated on the basis of the input signals and the performance maps stored in the ME control unit.

-----------------------------------------------------------------------------------------

Control of ignition system

The ME control unit actuates the ECI ignition system corresponding to the input signals and the performance maps stored in the ME control unit. The ME-SFI control unit calculates the ignition angle values and controls the anti-knock control (AKC).

-----------------------------------------------------------------------------------------

Voltage supply of ME-SFI control unit

Voltage supply to the ME control unit and to the engine control takes place via the relay terminal 87. The relay is connected to terminal 30 and receives a ground signal for ignition ON from the ME control unit. After ignition OFF the relay terminal 87 remains actuated for computer run-on. The signal ignition ON/OFF is received by the ME control unit from the EIS [EZS] control unit.

Voltage supply to the ME control unit takes place at terminal 87 and terminal 31 via three pins each switched in parallel. The components of the engine control are supplied via 3 fuses with terminal 87.



Terminal 30z to ME control unit is fused for model 219 by a fuse at the interior fuse box (F34). If there is a discontinuity relay terminal 87 and thus the engine control are nonfunctional.

-----------------------------------------------------------------------------------------

Interfaces

The ME control unit communicates with the following bus systems:

 CAN-B Passenger compartment data bus

 CAN-C Engine data bus

 CAN-S Sensors data bus

 LIN interface with alternator.

Computer run-on

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 run-on time with a warmed up engine is approx. 5 s, but may be extended to several minutes by various functions. After the fault memory has been cleared, the run-on time must expire.



Various engine operating information is transmitted via the

CAN databus from the ME control unit to the instrument cluster and to other control units which are connected to the CAN databus.

-----------------------------------------------------------------------------------------

Fuel injectors identifier

All injectors are marked with a 5 digit code on the plug connector and housing. After every exchange of an injector or control unit the code must be entered into the engine control unit using STAR DIAGNOSIS.

Voltage supply to fuel injectors

The voltage for the piezo fuel injectors of up to about 160 V is generated in the ME control unit using three voltage converters.

Channel 1: for cylinder 1 and 6

Channel 2: for cylinder 2 and 4

Channel 3: for cylinder 3 and 5



In the case of failure of a voltage converter misfires will occur on both associated cylinders. Short circuits to ground at the lines to the fuel injectors cause irreparable damage to the voltage converters.

-----------------------------------------------------------------------------------------

Positioner adaptation

If the ME control unit, EGR [ARF] actuator motors or the throttle valve actuator is replaced a positioner adaptation must be conducted using STAR DIAGNOSIS.

Diagnosis/DTC memory

The ME-SFI control unit checks its inputs and outputs for plausibility and recognizes possible faults. The following faults can be differentiated:

 Short circuits to ground or plus, open circuits

 Signal to small or too large

 Implausible combination of signals

 Actuation produces an implausible reaction.

The faults are erased in the ME-SFI control unit after circuit 30 is interrupted.

Actuations with STAR DIAGNOSIS

Functions can be actuated specifically for diagnostic purposes. These are listed in a menu item.

-----------------------------------------------------------------------------------------

Variant 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 STAR DIAGNOSIS.

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 data bus 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 data bus to the ME-SFI control unit.

-----------------------------------------------------------------------------------------

Proportion of homogeneous stratified charge operation

Values for a journey (in order for example to check after repair work whether stratified charge operation is released again) can be read out using STAR DIAGNOSIS.

In order to evaluate them over a longer period of time the total number of all ignitions is compared with the number of ignitions in stratified charge operation whereby the total number of all ignitions must be greater than 1 million. This represents at least about 2 to 3 hours of driving at medium rotational speeds. The values are reset by a discontinuity on terminal 30.

Fuel consumption signal

The consumption signal is calculated from the injection times (e.g. 8 liters/hour) and is transmitted via CAN to the trip computer in the instrument cluster.



The ME control unit is only functional with CAN data bus engine, CAN data bus interior and the drive authorization system FBS 3.

-----------------------------------------------------------------------------------------

Start recognition

The engine control unit is informed about the introduced starting procedure via the CAN message "circuit 50". This is essential, for example, for the following functions: rail pressure regulation, start quantity control, starter control, post-start enrichment and ignition timing when starting.

Engine speed signal

The ME control unit generates the short-circuit proof engine speed signal TNA from the signals supplied by the crankshaft position sensor, and outputs them to other control units. 3 pulses are output per engine revolution.