Knock Sensor: Description and Operation

Two piezo ceramic sensors are used on the MS41.1 Control Module to monitor engine knocking. The sensors are mounted on the block in the same location as the sensors on the Bosch engine management system. They function the same as those used on the Bosch system by producing a varying voltage relative to the degree of engine knock. The control module uses this input to maintain the engine's timing at the optimum point while avoiding engine knock.

The inputs from the knock sensors are continuously monitored as part of the OBD II emission requirements. The signals from the sensors are checked for plausibility by comparing them to stored values in the control module.

If a malfunction occurs, the control module incorporates an ignition timing safety margin which ensures that no damage will occur from engine detonation. The fault is stored in memory and the Check Engine Lamp will illuminate when the OBD II monitoring criteria is satisfied.