Self-diagnosis General The EDC system continuously checks itself by means of a signal-range check. During this check, all signals are scanned for presence and plausibility within a certain time frame (determined by the software). The control unit itself is also checked during the entire program run. The first check is al- ways carried out when the “ignition” is turned on. The diagnostic check lamp on the EDC operating element will come on for about 2 sec- onds. Any faults occurring during operation are stored for the purpose of subsequent diagnosis. A maximum of 5 faults can be stored simultaneously in the fault code memory. The faults are stored in the same order in which they occurred.
If more than 5 faults occur, the least significant fault is deleted. Fault storage includes D allocation of fault priority, D identification of the type of fault, D recording of fault frequency. Sporadic faults are recorded by a frequency counter the first time they occur. This means that a certain frequency number is set which is decremented by one during every start procedure. If the fault no longer occurs, it is deleted when the counter reaches zero. The diagnostic lamp lights steadily or goes out depending on the fault significance for the purpose of fault signalling. If several faults are stored, the steady light has priority over OFF . Only faults currently present are indicated.
Faults which are stored but are not currently present are not indicated. There are two fault code memories: D Fault code memory for diagnosis via ISO interface. This memory can be read and de- leted with MAN-Cats D Fault code memory for diagnosis via flash code. The flash code memory can be read out and deleted with the aid of the diagnosis button Faults are always entered in both fault code memories simultaneously and persist after the ignition has been switched off and on again. Indicator lamp check: The EDC indicator lamp lights for approx. 2 seconds after turning on the ignition as a lamp test. 23