SYSTEM OVERVIEW
Engine Control Module (ECM) monitors engine operation and contains a self-diagnostic system which stores Diagnostic Trouble Codes (DTCs) and complies with On-Board Diagnostics Generation-II (OBD-II) standards. The goal of OBD-II regulations is to provide vehicle with an on-board diagnostic system which is capable of continuously monitoring efficiency of emission control system, and to improve 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 vehicle emissions could rise above 1 1/2 times FTP standards.
If malfunction does not reoccur in 3 ignition cycles, MIL goes off, but DTCs remain recorded in ECM memory. DTCs may only be retrieved using an On-Board Diagnostic (OBD-II) scan tool that complies with SAE standard J-1978 or Lexus scan tool connected to Data Link Connector (DLC) No. 3. (Схема №1) Scan tool also provides freeze-frame data and can be used to clear codes.
Two-Trip Detection Logic
Two-trip detection logic is used to prevent erroneous malfunction detection. When a malfunction initially occurs, Diagnostic Trouble Code (DTC) will be temporarily stored in ECM memory, but MIL on instrument panel will not illuminate.
The second time that a malfunction is detected, MIL on instrument panel will illuminate, provided ignition is turned off and then back on after first malfunction was detected. This is referred to as 2-Trip Detection Logic and only applies to specified DTCs.
Note. When road testing vehicle in CHECK mode (Lexus scan tool only), Two Trip Detection Logic will be disabled, and MIL will illuminate first time a malfunction is detected.
CONNECTOR IDENTIFICATION
For wire color abbreviation definitions for manufacturer diagrams, see «WIRE COLOR IDENTIFICATION» table.
| Abbreviation | Wire Color |
|---|---|
| B | Black |
| BR | Brown |
| G | Green |
| GR | Gray |
| L | Blue |
| O | Orange |
| P | Pink |
| R | Red |
| W | White |
| Y | Yellow |
WIRE COLOR IDENTIFICATION
For connector identification for ECM connector views (Схема №22)