Identify sharp knocking sound! - audio clip

Posted this yesterday but don't see my own message - may be didn't get through. Need help if someone can identify the source of knocking sound in this audio clip (http://www.metricmind.com/misc/engine_sound.mp3) - Sienna 2010 w/80k miles on it gradually started making.
Disconnecting connector pointed to by red arrow on this photo (http://www.metricmind.com/misc/engine.jpg) makes sound almost disappear. Thanks in advance, Victor