TWO-TRIP DETECTION LOGIC
When a malfunction initially occurs, Diagnostic Trouble Code (DTC) will be temporarily stored in ECM memory but Malfunction Indicator Light (MIL) will not illuminate. The second time malfunction is detected, MIL will illuminate provided ignition is turned off and then back on after first malfunction was detected. This is referred to as "Two-Trip Detection Logic" and only applies to specific DTCs. When road testing vehicle in CHECK mode using Toyota hand-held tester, two-trip detection logic will not function and MIL will illuminate the first time a malfunction is detected.
DATA LINK CONNECTOR
OBD-II regulations (SAE J-1962) standardizes configuration of Data Link Connector (DLC) No. 3. DLC No. 3 is located under driver's side of instrument panel. (Scheme 66)
Scheme 66
FREEZE FRAME DATA
Engine Control Module (ECM) records engine operating conditions when a misfire or fuel trim (mixture) malfunction or when various other malfunctions exist. ECM records engine operating conditions for the fuel system, calculated load, engine coolant temperature, engine speed, vehicle speed and etc. when a malfunction exists. This information is referred to as freeze frame data. If more than one Diagnostic Trouble Code (DTC) exists, only freeze frame data for the first DTC is recorded. Freeze frame data is useful for determining conditions when a malfunction occurred. OBD-II scan tool or Toyota hand-held tester may by used to read freeze frame data.
SUMMARY
If no Diagnostic Trouble Codes (DTC) are present and a no start condition exists, proceed to BASIC DIAGNOSTIC PROCEDURES - 4-CYLINDER article. If no DTCs are present and a driveability condition exists, proceed to TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, ENGINE STALLS, etc.).