Mercury code p0325

SOURCE: 1998 mercury tracer, koer code

P0325 = Knock Sensor Circuit Malfunction.
A knock sensor tells the engine computer when one or more of your engine's cylinders are "knocking", that is, exploding the air/fuel mixture in a way that delivers less power and can be damaging to the engine if prolonged. The computer uses this information to tune the engine so that it doesn't knock.
In your case either the connector has failed, it's such a common failure to the extent that the connector is sold separately
http://www.car-stuff.com/1995mercurytracerknocksensor.htm
or the sensor itself has failed
http://www.partsgeek.com/catalog/1999/mercury/tracer/engine_electrical/knock_sensor.html