SFI SYSTEM > DIAGNOSIS SYSTEM

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DESCRIPTION FOR M-OBD
When troubleshooting Multiplex OBD (M-OBD) vehicles, the vehicle must be connected to the intelligent tester. Various data output from the vehicle's Engine Control Module (ECM) can then be read.
The Malfunction Indicator Light (MIL) is illuminated when the vehicle's on-board computer detects a malfunction in the computer itself or in drive system components. In addition, the applicable Diagnostic Trouble Codes (DTCs) are recorded in the ECM memory (Click here). If the malfunction does not reoccur, the MIL stays ON until the ignition switch is turned OFF, and then the MIL turns OFF when the ignition switch is turned ON. However, the DTCs remain recorded in the ECM memory.
To check the DTCs, connect the intelligent tester to the DLC3 (Data Link Connector 3) on the vehicle or connect terminals TC and CG on the DLC3 (DTCs will be displayed in the combination meter).
A093827E01
A099015E01

NORMAL MODE AND CHECK MODE
The diagnosis system operates in "normal mode" during normal vehicle use. In normal mode, 2 trip detection logic is used to ensure accurate detection of malfunctions. A "check mode" is also available to technicians as an option. In check mode, 1 trip detection logic is used for simulating malfunction symptoms and increasing the system's ability to detect malfunctions, including intermittent malfunctions (Click here).

2 TRIP DETECTION LOGIC
When a malfunction is first detected, the malfunction is temporarily stored in the ECM memory (1st trip). If the ignition switch is turned OFF and then ON again, and the same malfunction is still detected again, the MIL will illuminate (2nd trip).

FREEZE FRAME DATA
The freeze frame data records the engine conditions (fuel system, calculated engine load, engine coolant temperature, fuel trim, engine speed, vehicle speed, etc.) when a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.

CHECK DLC3
The vehicle's ECM uses the ISO 14230 (M-OBD) communication protocol. The terminal arrangement of the DLC3 complies with ISO 15031-03 and matches the ISO 14230 format.
If the result is not as specified, the DLC3 may have a malfunction. Repair or replace the harness and connector.
A004550E23
Symbols (Terminal No.)
Terminal Description
Condition
Specified Condition
SIL (7) - SG (5)
Bus "+" line
During transmission
Pulse generation
CG (4) - Body ground
Chassis ground
Always
Below 1 Ω
SG (5) - Body ground
Signal ground
Always
Below 1 Ω
BAT (16) - Body ground
Battery positive
Always
9 to 14 V

HINT:
Connect the cable of the intelligent tester to the DLC3, turn the ignition switch ON and attempt to use the intelligent tester. If the display indicates that a communication error has occurred, there is a problem either with the vehicle or with the tester.
  1. If communication is normal when the tester is connected to another vehicle, inspect the DLC3 on the original vehicle.
  1. If communication is still not possible when the tester is connected to another vehicle, the problem may be in the tester itself. Consult the Service Department listed in the tester's instruction manual.


INSPECT BATTERY VOLTAGE
If the voltage below 11 V, recharge the battery before proceeding.

Battery voltage:
11 to 14 V


CHECK MIL
A093827E01

  1. The MIL illuminates when the ignition switch is turned ON and the engine is not running.

    HINT:
    If the MIL does not illuminate, troubleshoot the MIL circuit (Click here).

  2. When the engine is started, the MIL should turn OFF. If the light remains ON, the diagnosis system has detected a malfunction or abnormality in the system.