Description of On-Board Diagnostics

ON-BOARD DIAGNOSTICS
- The recording condition of diagnostic trouble code After the ECM first detects a malfunction, a diagnostic trouble code is recorded when he engine is restarted and the same malfunction is re-detected. (Malfunction is detected in driving cycle). However, for fuel system rich/lean misfiring, a diagnostic trouble code is recorded on the first detection of the malfunction.
- The erasing condition of diagnostic trouble code. After recording the diagnostic trouble code, if the ECM does not re-detect the malfunction for 40 driving cycles, the diagnostic trouble code will be erased from the ECM memory. However, for fuel system rich/lean or misfiring, the diagnostic trouble code will be erased under the following conditions.
- When driving conditions (engine speed, engine coolant temperature, etc.) are similar to those when the malfunction was first recorded.
- When the ECM does not re-detect the malfunction for 80 driving cycles.

NOTE:
(1) A "driving cycle" consists of engine start-up, vehicle operation beyond the beginning of closed loop operation.

SELF-DIAGNOSIS
The ECM monitor the input/output signals (some signals at all times and the others under specified conditions). When the ECM detects that an irregularity, it memorize the diagnostic trouble code, and outputs the signal to the self-diagnosis output terminal. The diagnosis results can be read out Generic Scan Tool (GST). Diagnostic trouble code (DTC) will remain in the ECM as long as battery power is maintained. The diagnostic trouble code will however, be erased when the battery terminal or the engine control module (ECM) connector is disconnected or erased by Generic Scan Tool.