LR3/Disco 3
Engine Oil Temperature
Speed Control Switches (resistive ladders)
Vehicle Speed (via CAN bus)
Generator Monitor
Restraints Control Module
Manifold Absolute Pressure and Inlet Air Temperature
Outputs
The ECM outputs to the following:
Throttle Actuator
Fuel injectors (6)
EGR Valves
Engine Cooling Fan
Fuel pump relay
Starter Relay
Air conditioning condenser fan module
EMS Main Relay
Viscous Fan Control
Generator Control
The ECM connected to the vehicle harnesses via three connectors. The ECM contains data processors and memory
microchips. The output signals to the actuators are in the form of ground paths provided by driver circuits within the ECM.
The ECM driver circuits produce heat during normal operation and dissipate this heat via the casing. The fan in the E-box
assists with the cooling process by maintaining a constant temperature with the E-box. The fan is controlled by a
thermostatic switch located in the E-box. The E-box has pipe connections to the vehicle interior and receives additional
cooled air via the A/C system. Some sensors receive a regulated voltage supplied by the ECM. This avoids incorrect
signals caused by voltage drop during cranking.
The ECM performs self diagnostic routines and stores fault codes in its memory. These fault codes and diagnostics can
be accessed using T4. If the ECM is to be replaced, the new ECM is supplied 'blank' and must be configured to the
vehicle using T4. 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. If a fifteenth update is
required the ECM must be replaced. The current engine tune data can be accessed and read using T4.
When a new ECM is fitted, it must also be synchronised to the immobilisation control module using T4. ECM's cannot be
'swapped' between vehicles.
The ECM is connected to the engine sensors which allow it to monitor the engine operating conditions. The ECM
processes these signals and decides the actions necessary to maintain optimum engine performance in terms of
driveability, fuel efficiency and exhaust emissions. The memory of the ECM is programmed with instructions for how to
control the engine, this known as the strategy. The memory also contains data in the form of maps which the ECM uses
as a basis for fuelling and emission control. By comparing the information from the sensors to the to the data in the maps,
the ECM is able to calculate the various output requirements. The ECM contains an adaptive strategy which updates the
system when components vary due to production tolerances or ageing.
The ECM receives a vehicle speed signal on a CAN bus connection from the ABS Control Module. Vehicle speed is an
important input to the ECM strategies. The ABS control module derives the speed signal from the ABS wheel speed
sensors. The frequency of this signal changes according to road speed. The ECM uses this signal to determine the
following:
How much to reduce engine torque during gear changes.
When to permit speed control operation.
To control the operation of the speed control system.
Implementation of the idle strategy when the vehicle is stationary.
ECM Harness Connector C0872 Pin details
Pin No
Description
Input/Output
A1
Serial to immobilisation control module
Output
A2
Serial from immobilisation control module
Input
A3
CAN Low
Input/Output
