Diagnostic Trouble Code (DTC) Memory

When the engine control module (ECM) detects a fault, the diagnostic trouble code (DTC) and the status in the control module's diagnostic trouble code (DTC) memory are stored and are now visible at normal diagnostic trouble code (DTC) read off. If the diagnostic trouble code (DTC) indicates ignition off, the malfunction indicator lamp (MIL) indicates ignition off at the same time. If an existing fault disappears and does not return, the engine control module (ECM), after a number of fault-free operating cycles, depending on the fault code changes the status of the diagnostic trouble code (DTC). This means that it can no longer be read off at normal fault reading. In this status the diagnostic trouble code (DTC) remains until the engine control module (ECM) is cleared of diagnostic trouble codes (DTCs) or the power to it is switched off.