On-board Diagnosis System: General

The on-board diagnosis system detects and indicates a fault by generating a code corresponding to each fault location. The malfunction indicator light on the combination meter indicates occurrence of a fault or abnormality.
When the malfunction indicator light comes on as a result of detection of a fault by the ECM, the corresponding diagnostic trouble code (DTC) and freeze frame engine condition are stored in the ECM.
On the OBD-II conformable car, it is necessary to connect the SUBARU Select Monitor (SSM) or General Scan Tool (GST) to the data link connector in order to check the DTC.
The SSM and GST can be used for erasing DTCs. These can also read freeze frame data in addition to other pieces of engine data.
If there is a failure involving sensors, which may affect drive control of the vehicle, the fail-safe function ensures minimum level of drivability