The knock sensor detects abnormal vibration (spark knock or pinging) in the engine. The knock control system is designed to reduce spark knock during periods of heavy detonation. This allows the engine to use maximum spark advance to improve driveability. Knock sensors produce AC output voltage which increases with the severity of the knock. The signal is fed into the PCM and the timing is retarded to compensate for the severe detonation. On 1993 and 1994 models, the knock sensor is located on the right (rear) side of the engine block below the exhaust manifold. On 1995 and later models, the knock sensor is located below the intake manifold. To check, disconnect the knock sensor harness connector. Using an ohm-meter, check for continuity between the two terminals of the knock sensor connector. Continuity should be indicated. If an open circuit is indicated, replace the knock sensor. The knock sensor resistance is very high, use an ohmmeter cable of measuring at least 10 M-ohms. For 1993 and 1994 models, wait for the engine to cool completely before performing this procedure. Drain the cooling system. Raise the vehicle and support it securely on jackstands. Disconnect the knock sensor harness connector and detach any retaining clips. Remove the knock sensor from the engine block. Installation is the reverse of removal. Refill the cooling system. For 1995 and later models, remove the upper and lower intake manifold. Where necessary for access, remove the lower intake manifold as well. Disconnect the electrical connector from the knock sensor. Remove the sensor retaining bolt and the sensor from the engine block. Installation is the reverse of removal. Install the intake manifold.