Diagnostic Trouble Code Memory

When the engine control module (ECM) detects a fault, the diagnostic trouble code (DTC) and status are stored in the diagnostic trouble code (DTC) memory and are now visible at normal diagnostic trouble code (DTC) read out. If the diagnostic trouble code (DTC) lights the malfunction indicator lamp (MIL) this occurs at the same time. If an existing fault disappears and does not recur, the engine control module, after a certain number of fault-free operating cycles and depending on the DTC, changes the status of the diagnostic trouble code (DTC). This means that it can no longer be read off at normal DTC read out. In this status, the diagnostic trouble code (DTC) remains until the engine control module (ECM) erases diagnostic trouble code (DTC) or is disconnected from power.