Actually guy's, the indication on the ScanGuage, or any other OBD reader isn't cylinderhead temperature.

Your quite right that the sensor on Focus is CHT but the PCM takes that into account and adjusts the reading to what it considers to be a coolant temperature for the OBD datastream.

Same confusion for owners of fully electronic instrument clusters (all Focus). The temperature display isn't a gauge as with older units that used a dedicated sensor in the thermostat housing. Its more a 3 zone indicator, cold-running temp-hot programmed into the processor in the cluster reading the same OBD datastream.

Martin