Engine control (MR) function

W07.15-1441-76

Shown on engine 926.9

0 Ignition OFF

1 Circuit 15R ON

2 Circuit 15 ON

3 Circuit. 50

a) Engine control (MR)

b) Exhaust aftertreatment system with BlueTec diesel technology
- only for vehicles with code
(MS4) BlueTec 4 or
with code (MS5) BlueTec 5

c) Flame starting system (FLA)
- Only on vehicles with Code
(M89) Flame starting system

d) Drive control (FR)

A3 Drive control (FR) control unit

A4 Flame starting system control unit (FLA)

A6 Engine control (MR) control unit

A42 Immobilizer read-out electronics

A95 SCR frame module control unit

B10 Fuel temperature sensor

B15 Crankshaft position sensor

B16 Camshaft position sensor

B65 Coolant temperature sensor

Y6 Cylinder 1 unit pump

Y7 Cylinder 2 unit pump

Y8 Cylinder 3 unit pump

Y9 Cylinder 4 unit pump

Y10 Cylinder 5 plug-in pump

Y11 Cylinder 6 plug-in pump

Z3 Additional CAN star point

B111 Charge air temperature and boost pressure combination sensor

CAN 1 Vehicle CAN

CAN 4 Engine CAN

CAN 12 SCR CAN

M1 Starter

S1 Drive switch

S10 Start engine button

S11 Stop engine button

General information

The primary purpose of the engine control (MR) is to regulate and control injection of the pump-line-nozzle system (PLD system). It ensures that the engine is always running in the most fuel efficient, low pollutant and low noise emission manner possible under all operating conditions.

Function

The central control and regulator unit on the engine control (MR) is the engine control (MR) control unit (A6). It calculates the optimal beginning of injection according to the operating condition of the engine and the specified torque from the drive control (FR) as well as the injection quantity required for combustion. The engine control (MR) control unit (A6) also ensures that fuel is injected at exactly the right point in time and in the correct amount into the cylinder through exact, electrical actuation of solenoid valves in the unit pumps.

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The operating condition of the engine is determined based on input values from the following sensors:

 Fuel temperature sensor (B10)

 Crankshaft position sensor (B15)

 Camshaft position sensor (B16)

 Coolant temperature sensor (B65)

 Charge air temperature and boost pressure combination sensor (B111)

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While consumption, performance and exhaust gas quality relevant parameters are detected by the charge air temperature and boost pressure combination sensor (B111), the fuel temperature sensor (B10) and the coolant temperature sensor (B65), the engine control (MR) control unit (A6) detects the current rotational speed as well as the tightening angle relative to top dead center (engine position) via the crankshaft position sensor (B15) and also the compression cycle of cylinder 1 in combination with the camshaft position sensor (B16).

The required torque specified by the drive control (FR) control unit (A3) which is calculated from a number of inputs including the position of the foot throttle actuator (B1) passes over the engine CAN (CAN 4) to the drive control (MR) control unit (A6), which in turn sends the current engine torque and the maximum possible torque to the drive control (FR).

There is also the possibility via the engine CAN (CAN 4) and the drive control (FR) control unit (A3) to exchange information with other electronic systems or control units.

If the vehicle is also fitted with code (MS4) BlueTec 4 or code (MS5) BlueTec 5 there is a further CAN bus, the Selective Catalytic Reduction CAN (CAN 12) on the engine control (MR) control unit (A6). This can be used by the engine control (MR) control unit (A6) to exchange all information with the SCR frame module control unit (A95) which is necessary for controlling the exhaust aftertreatment system.

If a malfunction occurs on the engine CAN (CAN 4), the Selective Catalytic Reduction CAN (CAN 12) or a system component of the engine control (MR) or the exhaust aftertreatment system, the engine control (MR) will proceed according to an exactly established scheme depending on the severity of the malfunction. Thus it will fall back on replacement values for less severe faults such as the failure of a sensor while it will go into emergency mode for severe faults such as failure of the engine CAN (CAN 4).

The driver is able to at least drive to the nearest workshop if there is a fault in the system.