This Preliminary Information communication provides information to the technician about vehicles that may have a knock noise at idle that diminishes as the engine RPM is increased. Technician will need to remove accessory belt to verify noise is not accessory belt related, Check G109 for sufficient clamp load, remove G109 ground ring terminals and inspect for sticky glue substance covering the ground rings. When the knocking noise is occurring check 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 MAP 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. Also 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, and replace as necessary.
