Fault Detection and Trouble Code Memory Function

SELF-DIAGNOSIS
The ECM monitor the input/output signals (some signals at all times and the others under specified conditions). When the ECM detects 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 by the 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 negative terminal or the engine control module (ECM) connector is disconnected or erased by the Generic Scan Tool.

NOTE:
1 When battery voltage is low, diagnostic trouble codes can not be read. Be sure to check the battery for voltage and other conditions before starting the test.
2 Diagnosis memory is erased if the battery or the ECM connector is disconnected. Do not disconnect the battery before the diagnostic trouble codes are completely read and recorded.