SFI SYSTEM DIAGNOSIS SYSTEM

M-OBD

When troubleshooting a Multiplex On-Board Diagnostic (M-OBD) vehicle, the vehicle must be connected to the intelligent tester. Various data output from the ECM can then be read.

OBD regulations require that the vehicle's on-board computer illuminates the MIL on the instrument panel when the computer detects a malfunction in:

1. The emission control system/components.

2. The powertrain control components (which affect vehicle emissions).

3. The computer

   In addition, the applicable DTCs are stored in the ECM memory. If the malfunction does not recur in 3 consecutive trips, the MIL turns off automatically but the DTCs remain stored in the ECM memory.

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. "Check mode" is also available to technicians as an option. In check mode, "1 trip detection logic" is used for duplicating malfunction symptoms and increasing the ability of the system 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 same malfunction is detected during the next driving cycle, the MIL is illuminated (2nd trip).

FREEZE FRAME DATA

The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can be helpful in determining whether the vehicle was moving or stationary, whether the engine was warmed up or not, whether the air fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction.

DLC3 (Data Link Connector 3)

1. Check the DLC3 Click here.

INSPECT BATTERY VOLTAGE

If the voltage is below 11 V, recharge or replace the battery before proceeding to the next step.