Pontiac 12589867 Knock Sensor

Knock sensors in the engine sense unusual vibration and diminish spark knock. They give AC output voltage that increases with the severity of the knock. The PCM receives the signal and retards timing to compensate for detonation. The 4.2L six-cylinder engine has two knock sensors, with sensor 1 located towards the front and sensor 2 towards the rear. Knock sensor system can be affected by premium or high octane fuel, thus creating false codes. To replace the knock sensors, disconnect the negative battery terminal, raise vehicle and secure on jackstands. Disconnect knock sensor electrical connector and remove sensor bolt. For V8 models from 2002 to 2004, remove intake manifold and detach grommets and electrical connector off valley cover. Take out knock sensors from engine block. For V8 models from 2005 and later, disconnect negative battery cable, raise vehicle and support on jackstands. Disconnect electrical connector and take out right side knock sensor from cylinder block. Repeat for left side.