Engine management system

ENGINE MANAGEMENT SYSTEM

The Engine Control Module (ECM) monitors the conditions required for optimum combustion of fuel in the cylinder through sensors located at strategic points around the engine. As a result of these sensor inputs, the engine control module can adjust the fuel quantity and timing of the fuel being delivered to the cylinders.

The main features are as follows:

• A single ECM controls the fuel injection system and the ignition system. The ECM incorporates short circuit protection and can store intermittent faults on certain inputs. TestBook can interrogate the ECM for these stored faults.
• The ECM is electronically immobilised which prevents the engine from being started unless it receives a coded signal from the anti-theft control unit.
• In conjunction with the throttle position sensor the ECM uses the speed/density method of air flow measurement to calculate fuel delivery. This method measures the inlet air temperature and inlet manifold pressure and assumes that the engine is a calibrated vacuum pump, with its characteristics stored in the ECM, it can then determine the correct amount of fuel to be injected.
• The vehicle diagnostic connector allows engine tuning or fault diagnosis to be carried out using TestBook without disconnecting the ECM harness multiplug.
• The ECM harness multiplug incorporates specially plated pins to minimise oxidation and give improved reliability.
• The ECM controls the operation of the radiator and air conditioning cooling fans, based on signals received from the engine coolant temperature sensor.
• If certain system inputs fail, the ECM implements a back-up facility to enable the system to continue functioning, although at a reduced level of performance.

IGNITION SYSTEM

The ECM determines the optimum ignition timing based on the signals from the following sensors:

1. Crankshaft position sensor - Engine speed and crankshaft position
2. Manifold absolute pressure sensor - Engine load
3. Engine coolant temperature sensor - Engine temperature
4. Throttle position sensor - Throttle pedal released

The engine management system uses no centrifugal or vacuum advance. Timing is controlled by the ECM which is energised by the main relay, located within the relay module. Spark distribution is achieved by a direct ignition system which consists of a twin-ignition coil driven directly from the ECM.