The fault memory is a functionality offered by most control units. If a malfunction of the control unit, connected sensors or actuators is detected or implausible data is received from other control units, this is noted in the error memory.

The fault memory of the respective control unit therefore provides valuable information for troubleshooting. Stupid people delete the respective fault memory without thinking instead of correcting the cause of the error. In the case of a large number of stored errors, where it is not clear when and in what context they occurred, it can be useful to clear the error memory and check which errors are coming back or are even acute.

A diagnostic system for reading out the fault memory is part of the basic equipment of a workshop for current vehicles. It is also useful for private individuals to avoid unnecessary repairs.

Example on an engine control unit and the diagnostic software VCDS with manufacturer-specific diagnosis:

When diagnosing via OBD-2, emission-related faults in the engine control unit can be read out: