Diagnostic Trouble Code (DTC) Memory

When the engine control module (ECM) detects a fault, the diagnostic trouble code (DTC) is stored with the qualifier and status in the unit DTC memory. For certain types of diagnostic trouble codes (DTCs) the missing signal is replaced with a substitute value so that the system can continue to operate.

If the fault disappears, the diagnostic trouble code (DTC) will be present for a longer time in the diagnostic trouble code (DTC) memory although the status of the code will have changed.