Subaru 2002 Impreza Service Manual page 86

ON-BOARD DIAGNOSIS SYSTEM
Fuel lniection (Fuel Svstem)
6. On-board Diagnosis System
A: GENERAL
0
The on-board diagnosis system detects and indicates a fault by generating a code correspond-
ing to each fault location. The malfunction indicator lamp (CHECK ENGINE light) on the combina-
tion meter indicates occurrence of a fault or abnormality.
0
When the malfunction indicator lamp 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.
0
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.
0
The SSM and GST can read and erase DTCs. They can also read freeze frame data in addition
to other pieces of engine data.
0
If there is a failure involving sensors which may affect drive control of the vehicle, the fail-safe
function ensures minimum level of driveability.
B: FAIL-SAFE FUNCTION
For a sensor or switch which has been judged faulty in the on-board diagnosis, the ECM, if ap-
propriate, generates an associated pseudo signal to keep the vehicle operational. (The control
becomes degraded.)
FU-36