P0331 Cadillac Code - Knock Sensor Performance Bank 2

The Knock Sensor system enables the Engine Control Module (ECM) to control the ignition timing for the best possible performance while protecting the engine from potentially damaging levels of detonation, also known as spark knock. The knock sensor system uses one or two flat response 2-wire sensors. The sensor uses piezo-electric crystal technology that produces an AC voltage signal of varying amplitude and frequency based on the engine vibration or noise level. The amplitude and frequency are dependent upon the level of knock that the knock sensor detects. The ECM receives the knock sensor signal through two isolated signal circuits for each knock sensor.
The control module learns a minimum noise level, or background noise, at idle from the knock sensor and uses calibrated values for the rest of the RPM range. The control module uses the minimum noise level to calculate a noise channel. A normal knock sensor signal will ride within the noise channel. As engine speed and load change, the noise channel upper and lower parameters will change to accommodate the normal knock sensor signal, keeping the signal within the channel. In order to determine which cylinders are knocking, the control module only uses knock sensor signal information when each cylinder is near the Top Dead Center (TDC) of the firing stroke. If a knock is present, the signal will range outside of the noise channel.
If the control module has determined that a knock is present, it will retard the ignition timing to attempt to eliminate the knock. The control module will always try to work back to a zero-compensation level, or no spark retard. An abnormal knock sensor signal will stay outside of the noise channel or will not be present. knock sensor diagnostics are calibrated to detect faults with the knock sensor circuitry inside the control module, the knock sensor wiring, or the knock sensor voltage output. Some diagnostics are also calibrated to detect constant noise from an outside influence such as a loose/damaged component or excessive engine mechanical noise.
The Diagnostic Trouble Code (DTC) will be set when the signal from Knock Sensor is low frequency.

• Faulty Knock Sensor 2 Bank 2
• Knock Sensor 2 Bank 2 circuit poor electrical connection
• Knock Sensor 2 Bank 2 harness is open or shorted
• Faulty Engine Control Module (ECM)