At the peak of the block, in the dingle between the heads of cylinders and right under the manifold, we find the knock sensor. In 2007 and beyond G35 Sedans as well as 350Z models, there are two knock sensors which are positioned in this same region. First, remove the intake manifold plenum assembly to have it replaced. Then, remove the fuel rail along with fuel injector assembly. After that removed is intake manifold itself. Disconnect electrical connector from knock sensor. To take out a knock sensor, push down on release tab and unplug an electrical connector, then get rid of a fixation screw for a knock sensor bolt and take a sensor out of a cylinder block. Get rid of a fixture screw for mounting bolts, then remove mounting bolts themselves. Installation is opposite to removals. Make sure you tighten down the pinch bolt for a knock sensor securely so as to create that desired torque value only when needed will there be correct tightness.