Engine Control Module: Description and Operation

The KV6 engine is fitted with a Siemens MS43 Engine Management System (EMS), which is an adaptive system that maintains engine performance at the optimum level throughout the life of the engine.

The EMS consists of an Engine Control Module (ECM) that uses inputs from engine sensors and from other vehicle systems to continuously monitor driver demand and the current status of the engine. From the inputs the ECM calculates the Air Fuel Ratio (AFR) and ignition timing required to match engine operation with driver demand, then outputs the necessary control signals to the electric throttle, fuel injectors and ignition coils. The ECM also outputs control signals to operate the:

- Air Conditioning (A/C) compressor.
- Engine cooling fans.
- Evaporative emissions (EVAP) purge valve and Diagnostic Module for Tank Leakage (DMTL).
- Fuel pump.
- Variable Intake System (VIS).

The ECM also interfaces with the:

- Immobilisation ECU, for re-mobilisation of the engine fuel supply.
- Cruise control interface ECU, to operate cruise control.
- Electronic Automatic Transmission (EAT) ECU, to assist with control of the gearbox.

Sensor inputs and engine performance are monitored by the ECM, which illuminates the SERVICE ENGINE SOON (MIL) and/or the SERVICE ENGINE warning lamps in the instrument pack if a fault is detected.

As part of the security system's immobilisation function, a vehicle specific security code is programmed into the ECM and the immobilisation ECU during production. The ECM cannot function unless it is connected to an immobilisation ECU with the same code. In service, replacement ECM's are supplied uncoded and must be configured, using T4, to learn the vehicle security code from the immobilisation ECU.

A "flash" Electronic Erasable Programmable Read Only Memory (EEPROM) allows the ECM to be externally configured, using T4, with market specific or new tune information up to 14 times. The current engine tune data can be accessed and read using T4.

The ECM memorises the position of the crankshaft and the camshaft when the engine stops. During cranking on the subsequent start the ECM confirms their positions from sensor inputs before initiating fuel injection and ignition.

To achieve optimum performance the ECM is able to 'learn' the individual characteristics of an engine and adjust the fuelling calculations to suit. This capability is known as adaptive fuelling. Adaptive fuelling also allows the ECM to compensate for wear in engine components and to compensate for the tolerance variations of the engine sensors.

If the ECM suffers an internal failure, such as a breakdown of the processor or driver circuits, there is no back up system or limp home capability. If a sensor circuit fails to supply an input, where possible the ECM adopts a substitute or default value, which enables the engine to function, although with reduced performance in some cases.