2001 - 2003 ford Ranger 2.3 L, ALSO -ford focus 2005 -2010 2.0 L, ALSO - Mazda B2300 2.3 L

The coolant sensor temperature is usually found just beneath the cylinder head, on the engine block.

You just disconnect the 1-2 wires and then undo it with a wrench.
The sensor will look like one of these:
1999 Chevy Lumina ltz 3 8 v6 coolant temperature sensor Google Search

Just be aware .. you may have TWO such sensors on your vehicle.

One sensor (usually with 3-4 electrical pins) is near the thermostat and works in conjunction with other sensors to regulate fuel/air according to engine temperature.

The other type of sensor is in the block near the cylinder head. It sends a signal to the temperature gauge on your dashboard ONLY. If your temp gauge constantly reads too hot or too cold .. this one is the culprit.
If it's a running fault .. speed .. rough running .. fuel. It may look like this:

trapped air. When temp needle climbs to 1/4 way, loosen coolant temp sensor to bleed off trapped air in cylinder heads. Air is gone once coolant starts to stream out, but only open slightly at a time. May have to do in increments as trapped air will cause rapid overheat

Sounds like a temp sensor or wiring problem.
You may only have one sensor for both the gauge and the engine computer.
If the computer temp sensor fails, or is not sending a signal to the engine computer, the fans will run as a precaution to keep the engine from overheating.
If you have replaced the correct sensor, it could be a wiring problem, or the engine coolant could be low enough to not touch the sensor.
If the coolant sensor is not sending a signal, the check engine light should also be on.

sounds like the thermostat is stuck shut..unless the head gasket is blown somewhere.. it will pump the antifreeze level down to form an air pocket.. this will cause overheating constantly check each cylinder for even compression..the lowest reading will most likely be the blown cylinder..

The Engine Temp. sensor is bad. it is under the intake manifold. if there is a miss also check under the coils over the spark plugs. If there is Coolant in the spark plug holes .then the intake gasket is leaking. The intake manifold needs to come off to change the coolant sensor. When off look for corrosion on the cylinder head at the coolant port. If there is corrsion then the cylinder head must be replaced.