System Overview
WARNING: This page is about a different car, the 1996 Toyota Supra. However, it is still accessible from the selected car via links, so may be relevant.
The ECM monitors engine operation and contains a self-diagnostic system which stores Diagnostic Trouble Codes (DTCs). Self-diagnostic system is used to provide vehicle with an on-board diagnostic system which is capable of continuously monitoring the efficiency of emission control system, and to improve diagnosis and repair when system failures occur.