Description of on-Board Diagnostics
ON-BOARD DIAGNOSIS SYSTEMA: GENERAL
- The on-board diagnosis system detects and indicates a fault in various inputs and outputs of the complex electronic control. The malfunction indicator lamp (CHECK ENGINE light) on the instrument panel indicates occurrence of a fault or trouble.
- When the malfunction indicator lamp comes on by the ECM having diagnosed occurrence of faults, the diagnostic trouble code (DTC) and the 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 data link connector in order to check the DTC.
- The SSM and GST not only can read out the DTC but also can erase the DTC or read out the freeze frame data and other pieces of engine data.
- Further, against such a failure or sensors as may disable the drive, the fail-safe function is provided to ensure the minimal driveability.
B: FAIL-SAFE FUNCTION
For the part which has been judged faulty in the on-board diagnosis, the ECM generates the associated pseudo signal (only when convertible to electric signal) and carries out the computational processing. In this tashion, the fail-safe function is performed.