Computers and Control Systems: Description and Operation

Engine Diagnosis General Description
This vehicle is equipped with an engine and emission control system which are under control of ECM.

The engine and emission control system in this vehicle are controlled by ECM. ECM has an On-Board Diagnostic system which detects a malfunction in this system and abnormality of those parts that influence the engine exhaust emission. When diagnosing engine troubles, be sure to have full understanding of the outline of "On-Board Diagnostic System Description" and each item in "Precautions in Diagnosing Trouble for Engine" and execute diagnosis according to "Engine System Check".

There is a close relationship between the engine mechanical, engine cooling system, ignition system, exhaust system, etc. and the engine and emission control system in their structure and operation. In case of an engine trouble, even when the malfunction indicator lamp (MIL, "CHECK ENGINE" lamp) doesn't turn ON, it should be diagnosed according to this flow.