Malfunctions and self-diagnosis (Audi 100 C4)

The injection system control unit can recognize and record exactly 30 types of faults in the fault memory. It records whether the fault is permanent or sporadic. Records of sporadic faults are erased after 50 engine starts, if the sporadic fault does not reappear. In case of a suspected ignition/injection system defect, it is necessary to contact a workshop to read the fault memory data. The fault memory must be cleared in a workshop after the repair is completed.

Note: MPFI injection system control unit (2.6 liter engine) remains active for another hour and a half after the ignition is switched off. This means that any injection system defect that occurs during this time is also recorded in the fault memory. The disconnected plug is also recognized as a defect.

But the above does not mean that you should wait an hour and a half every time before starting the repair. After all, such an interruption as a malfunction occurs only once and, therefore, falls into the "box" for sporadic (arising from time to time) malfunctions, the record of which is erased again.

(The text is based on materials from the website: «AUDIMANUAL»)