Where is knock sensor located on a 2003 Chevy venture van?

Quite frankly no you don’t need to know where the “knock sensor” is located - simply because they do not pose any problems on that engine! Before retirement - I was in the auto repair business for a VERY LONG TIME - nary a knock sensor failure on the 3.1L or the 3.4L GM - - period.. I see you stated “it knocks when it runs” - that is a mechanical failure - not a sensor. Recommend having knowledgeable mechanic listen to the engine for *hands-on* evaluation. Good luck!