System Overview

Engine Control Module (ECM) monitors engine operation and contains a self-diagnostic system which stores Diagnostic Trouble Codes (DTC) and complies to On-Board Diagnostics Generation II (OBD-II) standards.

Self-diagnostic system is used to provide vehicle with an on-board diagnostic system which is capable of continuously monitoring efficiency of emission control system, and improving diagnosis and repair when system failures occur.

Federal Test Procedure (FTP) sets maximum allowable emission standards. A Malfunction Indicator Light (MIL) must illuminate if a system or component either fails or deteriorates to a point where the vehicle emissions could increase to more than 1 1/2 times FTP standards.

If malfunction does not reoccur in 3 consecutive trips, MIL goes off, but DTCs remain recorded in ECM memory. DTCs may only be retrieved using an On-Board Diagnostic-II (OBD-II) scan tool that complies with SAE standard J-1978 or Toyota hand-held tester connected to Data Link Connector (DLC) No. 3. Scan tool also provides freeze frame data and can be used to clear DTCs.