ECM critical inputs

Petrol engine management diagnosis

In order to initialise the engine management system, the engine electronic control module - ECM first needs to receive several inputs in a specific order, starting with an ignition live voltage supply to wake up the ECM.

Main system relay and fuel pump relay are also energised by the ECM in a specific sequence and in response to inputs received.

The power supply to the ECM is sub divided between ignition live, permanent live and several earth connections which include power ground, sensor grounds and reference grounds.

The first dynamic input to the ECM comes from the crankshaft position - CKP sensor. This input provides both engine speed as well as a crankshaft position reference. It is a primary input to enable the ECM to begin its fuelling and timing calculations.

Understanding the sequence of critical inputs to the engine ECM and how to test them effectively is of paramount importance, particularly when investigating faults whereby the engine will not start.

The course explains in detail the the function of each critical input, its utilisation by the ECM, how to test the inputs, carry out useful quick checks and understand what to look for.

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