This Preliminary Information communication provides information to the technician about vehicles that have a knock noise at idle that diminishes as the engine revolutions per minute is increased. Technician will need to remove the accessory belt to verify noise is not accessory belt related. Technician will need to inspect the G109 for sufficient clamp load also inspect for a clean matting surface. When the knocking noise is occurring, see if the timing is being retarded and if there is knock sensor activity. Disconnect the knock sensor and see if the noise changes. If timing retards and noise changes with knock sensor disconnected, reconnect knock sensor and disconnect Manifold Absolute Pressure sensor and see if the knocking noise is affected. If noise is not affected remove both camshaft actuators and inspect if the camshaft dowel pin is damaged, if so replace actuator and camshaft. If noise is affected or no problem found with the camshaft dowel pin, remove the piston rod assemblies and check for excessive clearance in the piston pin bushing, replace as necessary.
