Permanent Diagnostic Trouble Code (DTC)

WARNING: This page does not describe the selected car, but rather 32 other vehicles, including the 2009 Mercury Mountaineer, 2009 Mercury Milan, 2009 Mercury Mariner, 2009 Mercury Grand Marquis, and 2009 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.

The software stores a permanent DTC in non-volatile random access memory (NVRAM) whenever a DTC is set and the malfunction indicator lamp (MIL) has been illuminated. Permanent DTCs can only be cleared by the module strategy itself. After a permanent DTC is stored, three consecutive test passed monitoring cycles must complete before the permanent DTC can be erased. The PCM clears the permanent DTCs after one monitoring cycle if a request to clear DTCs is sent by the scan tool and the test subsequently runs and passes. A permanent DTC cannot be erased by clearing the keep alive memory (KAM). The intended use of the permanent DTC is to prevent vehicles from passing an in-use inspection simply by disconnecting the battery or clearing the DTCs with a scan tool prior to the inspection. The presence of the permanent DTCs at an inspection without the MIL illuminated is an indication that a correct repair was not verified by the onboard monitoring system.