I had my knock sensors replaced about a month or two ago and now my check engine light is back on and im getting a p0325 which I heard could be the harness. How do i know for sure? where is the harness?

 

P0325 is Left Bank Knock Sensor or Circuit is Open or Shorted, Basically, it can be the sensor or the harness which includes the plug and wires from the sensor itself to the ECM. I think there is a short "Y" section under the manifold that is easily replaceable though. I actually did this job on my GS430 years ago and remember replacing the harness too.

There is much information on Knock Sensors and P0325 in the 2GS forum. If you search "P0325" you will find THIS THREAD which has knock sensor information.

My car when I was replacing the Knock Sensors and Harness.

 

Did you use true OEM knock sensors from Lexus? Generally that's why the code reappears. I had mine done at the dealer about a year ago (pricey to be sure) and haven't had a problem since.