Electronic Control Module (ECM): Freelander
The Engine Control Module (ECM) is a Siemens MS43, which is an adaptive system that maintains optimum engine performance throughout the vehicle life. The ECM uses inputs from engine sensors and from other vehicle systems to continuously monitor driver demand and current engine status. Using inputs, the ECM calculates the air/fuel mixture and ignition timing, then outputs the necessary control signals to the electric throttle, fuel injectors and ignition coils. The ECM also outputs control signals to operate the:
- A/C compressor.
- Engine cooling fans.
- EVAP purge valve and Diagnostic Module for Tank Leakage (DMTL).
- Fuel pump.
- Variable Intake System (VIS).
- Immobilization Electronic Control Unit (ECU), for engine fuel supply reactivation.
- Cruise control.
- Electronic Automatic Transmission (EAT) Electronic Control Unit (ECU).
A fault is indicated by illumination of the Malfunction Indicator Light (MIL). Part of the security system immobilization function is a vehicle specific security code programmed into the ECM and the immobilization ECU. The ECM cannot function unless it is connected to an immobilization ECU with the same code. Replacement ECMs are supplied uncoded and must be programmed using TestBook/T4 to learn the vehicle security code from the immobilization ECU. An Electronic Erasable Programmable Read Only Memory (EEPROM) allows the ECM to be externally configured, using TestBook/T4.
The ECM memorizes the position of the crankshaft and the camshaft when the engine stops. During cranking on the next engine 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. This ECM capability is known as adaptive fueling. Adaptive fueling also allows the ECM to compensate for engine wear and compensate for tolerance variations of engine sensors. If the ECM has an internal failure (processor or driver circuits), there is no back-up or limp home capability. If a sensor circuit fails to supply an input, the ECM adopts a substitute or default value (where possible), which enables the engine to function with reduced performance.
The ECM is located in the engine compartment, in the E-box. An electric fan ventilates the E-box with air from the passenger compartment. Exhaust air from the E-box is directed back into the passenger compartment. Cooling fan operation is controlled by a thermostatic switch in the E-box. The thermostatic switch receives a power feed when ignition is on. If the E-box temperature reaches 95°F (35°C). the thermostatic switch closes and connects the power feed to the fan, which cools the E-box with air from the passenger compartment. When the temperature in the E-box decreases to 81°F (27°C), the thermostatic switch opens, stopping the fan. In colder climates, to prevent the fan seizing up where it may not operate for long periods of time, the fan receives a power feed direct from the starter circuit so that it runs each time the engine is cranked.