We have had a knocking sensor code triggered on our Frontier on Bank 1 Sensor 1 and Bank 2 Sensor 1. We replaced all 4 oxygen sensors (Bank 1 Sensor 1, Bank 2 Sensor 1, Bank 1 Sensor 2 and Bank 2 Sensor 2) and the knocking sensor code has been triggered once again. I have put in Denso sensors and Bosch sensors and replaced them three times with the same result.

It is now giving the following codes:
P0325 (Knock Sensor 1 Circuit Malfuntion)
P0131 (O2 Sensior B2 S1 Circuit Low Volt) and
P0151 (O2S Low Volt (Bank 1 Sensor 1).

What do you recommend our next steps to be?

Have you tried replacing the Knock Sensor itself?

No, I have not yet replaced the knocking sensor itself.

The Knock Sensor, then, is likely the problem and should be replaced.