Hard Failures
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 1993 Volkswagen Fox, 1992 Volkswagen Fox, 1991 Volkswagen Fox, 1990 Volkswagen Fox, and 1989 Volkswagen Fox. However, it is still accessible from the selected car via links, so may be relevant.
On Fox, the Digifant I electronic control unit used in California vehicles is equipped with a permanent fault memory. If a fault occurs in monitored sensors and components, they store a fault in memory.
If malfunctions are present for more than 5 seconds, they are stored as Diagnostic Trouble Codes (DTCs) and will be displayed as a permanent malfunction even though the malfunction is not occurring at the time DTCs are displayed. Malfunctions that affect oxygen sensor control can only be read accurately after a test drive of at least 5 minutes.