Knock Module in Control Unit
The module has the task of continually monitoring the knock sensor signal. If knock is recognized, it produces a square pulse which can be evaluated by the control unit software.
The knock module (SNEF module) is located directly in the control unit, as in the C 16 XE engine.
If knock occurs, the knock module output sinks from 9 V to 0 V. The duration of the pulse generated by the module is proportional to the knock intensity.
If the module output signal remains at 0 V (low) for longer than 4 s, the control unit assumes that a malfunction has occurred and switches over to the 91 RON characteristic map. In addition, the firing angle is retarded by
5 °CA in the interests of safety.