On the 2003 Mercury Sable, the P0193 is a fairly straight forward code pointing to a problem with the Fuel Rail Pressure Sensor. The sensor is located on the end of the fuel rail. Carefully inspect the vacuum line for any cracks, holes or disconnections. Inspect the electrical connector for any loose, broken or damaged wires. If no problems are found, check the actual fuel pressure. If the pressure is withing specs, replace the fuel rail pressure sensor.
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