* Coolant Temperature Sensor (CTS): This is the most likely sensor you're thinking of, and it's the one that tells the engine computer (if equipped) and gauge what the engine coolant temperature is. This sensor is usually located on the cylinder head, often near the thermostat housing. The exact position varies greatly depending on the engine (e.g., 300 inline-six, 302 V8, 460 V8, etc.). You'll need to consult a repair manual specific to your truck's engine to pinpoint its location.
* Intake Air Temperature (IAT) Sensor: This sensor measures the temperature of the air entering the engine. Its location is typically in the intake air stream, often near the throttle body or air filter housing. Again, precise location will vary by engine.
To find the specific location of your truck's temperature sensor(s), you'll need to:
1. Identify your engine: Find the engine size (e.g., 302, 460) on your vehicle's identification plate (often in the driver's side door jamb).
2. Consult a repair manual: A Haynes or Chilton repair manual for your specific year, make, model, and engine will have diagrams showing the sensor locations. You can also find some diagrams online, but a dedicated manual is the most reliable source.
3. Look at online forums: Search online forums specific to 1991 Ford trucks (with your engine type specified) for pictures and descriptions of sensor locations.
Without knowing the specific engine in your 1991 Ford truck, it's impossible to give a precise answer.
