Fault memory
The fault memory is part of a control unit in modern vehicles that have an OBD interface . It stores the record of malfunctions or technical defects in the vehicle.
To do this, the control units check the measured values they receive for the plausibility of their numerical values, for example, or check them specifically for possible errors such as a sensor interruption , short circuit of the sensor to ground or short circuit of the sensor to positive . An example of other types of faults that are not based on the on- board electronics itself is a prolonged lack of engine oil .
Errors detected in this process are stored in a non-volatile manner, for which purpose EEPROMs are mostly used. Each control unit only saves its own errors, so in reality there are a number of independent error memories in a vehicle.
A distinction is made between static and sporadic errors in the errors to be saved . The difference is that sporadic errors are automatically deleted again if they no longer occur over a certain number (e.g. 50) of driving cycles (here in the sense of switching the ignition on and off again). For this purpose, driving cycle counters for each possible error are recorded in the error memory.
In automotive workshops, the fault memory can be read out with the help of diagnostic testers, data loggers and vehicle diagnostic systems in order to shorten the fault diagnosis . Depending on the vehicle, either all existing control units are queried automatically or they have to be addressed individually by hand. After the fault has been rectified, the fault memory is reset or deleted.
literature
- Karl-Heinz Dietsche, Thomas Jäger, Robert Bosch GmbH: Automotive pocket book. 25th edition, Friedr. Vieweg & Sohn Verlag, Wiesbaden, 2003, ISBN 3-528-23876-3
- Robert Bosch (Ed.): Autoelectronics Autoelectronics. 5th completely revised and expanded edition. Vieweg & Sohn Verlag, Wiesbaden 2007, ISBN 978-3-528-23872-8
- Werner Zimmermann and Ralf Schmidgall: Bus systems in vehicle technology - protocols, standards and software architecture . Vieweg + Teubner, 4th edition, 2010, ISBN 978-3-8348-0907-0