303-14C Electronic Engine Controls- 2.7L Diesel: Description And Operation (page 8 of 23)

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