Changing oil for the first time on recently purchased 2000 Accord EX coupe, found a single prong wire with a green top hanging by oil filter, any idea where it goes & purpose?

 

probally knock sensor wire thats not connected. its right above the filter take the plug and connect it

 

I don't recall F23 engines having knock sensor. Could be the thermostat housing sensor or VTEC Pressure Switch connector if I remember right.

 

I believe you are right about knock sensor. Got autozone guy to check codes. It did show a knock sensor issue which was giving a Vtec code also. Also found the check engine light is not working. Suprise!! Thanks for the replies