The knock sensor is like your fingertips if you poke them it tells your brain to tell your mouth to scream OUCH. So in engine terms if your tps is bad then your car stumbles and the engine feels the pain so your knock sensor triggers you CEL and you have it checked. Replace the hose under the EGR it is broken for sure. You can do it yourself and only spend $1 for the 3-4 inch hose. The knock sensor code will clear it self once the egr hose is fixed. If not have the shop clear it for you but do not FIX IT. You will still get a code if the van has the egr problem. ITS ONLY FUNCTION IS TO CHECK FOR VIBRATION WHICH IS CAUSED BY OTHER PROBLEMS IT IS ALWAYS IN SLEEP MODE AND ONLY WORKS WHEN THERES A PROBLEM. IN FACT HAVING A CODE FROM THE KNOCK SENSOR IS GREAT THAT WAY YOU KNOW TO LOOK OUT FOR PROBLEM.