Knock Sensor Circuit Trouble Code

NAME OF CODE:
Knock Sensor Circuit

WHEN MONITORED:
With the ignition ON and the engine running.

SET CONDITION:
The knock sensor circuit voltage (cavity 27) falls below a minimum value at idle or deceleration. The minimum value is from a look-up table internal to the Powertrain Control Module (PCM) and is based on engine RPM. The trouble code also sets if the sensor output is above 5.0 volts.

THEORY OF OPERATION:
The knock sensor is mounted on the cylinder block below the intake manifold. The knock sensor is comprised of thin piezo-electric ceramic discs bonded to a metal diaphragm. When engine knock occurs, the diaphragm vibrates along with the piezo-electric discs, producing an electrical signal. The signal is used by PCM cavity 27 to adjust ignition timing to eliminate the knock condition.

POSSIBLE CAUSES:
- Sensor signal open
- Sensor internally open
- PCM failure
- Sensor signal circuit shorted to ground