Where is the coolant temperature sensor located on my 1994 Saab 900S 2.0 T engine There is a Coolant Temperature Sensor for Gauge that I located and there is a Coolant Temperature Sensor that sends signal to the Fuel Control Module that causes to change fuel mixtures. I have not been able to locate this sensor.

No , their arn't two coolant temp. sensors . One near the thermostat housing . The Temp sensor is a input to the PCM / ECM . The PCM / ECM needs the temp info for fuel calculations . The temp gauge on the instrument cluster gets this info over class 2 serial data network Hooking up a factory or professional scan tool that can read sensor data is the easy way to diagnose ,not guessing . Looking at factory service info. an wiring diagrams too see what is what is another way . You have no clue ,take it to a qualified repair shop.

The engine coolant temperature sensor is a thermistor (a resistor which changes value based on temperature) mounted in the engine coolant stream. Low coolant temperature produces a high resistance (100,000 ohms at -40°C/-40°F) while high temperature causes low resistance (70 ohms at 130°C/266°F).
The PCM supplies a 5 volt signal to the engine coolant temperature sensor through a resistor in the PCM and measures the voltage. The voltage will be high when the engine is cold, and low when the engine is hot. By measuring the voltage, the PCM calculates the engine coolant temperature. Engine coolant temperature affects most systems the PCM controls.
The scan tool displays engine coolant temperature in degrees. After engine startup, the temperature should rise steadily to about 90°C (194°F) then stabilize when thermostat opens. If the engine has not been run for several hours (overnight), the engine coolant temperature and intake air temperature displays should be close to each other. A hard fault in the engine coolant sensor circuit should set DTC P0117 or DTC P0118; an intermittent fault should set a DTC P1114 or P1115. The DTC Diagnostic Aids also contains a chart to check for sensor resistance values relative to temperature.
The ECT sensor also contains another circuit which is used to operate the engine coolant temperature gauge located in the instrument panel.

What diognostics say its a sensor ?????? No diagnostic's ever tell's you it's a sensor . You as a technician would need to prove that by testing electrical circuits , viewing coolant temp sensor . Hooking scan tool and trying to command the gauge with by directional control . The temp gauge not showing any temp. ? No movement ? Engine Coolant Temperature Gage Inaccurate or InoperativeStep Action
Yes
No
Schematic Reference: Instrument Cluster Schematics
1
Did you perform the Instrument Cluster Diagnostic System Check?
Go to Step 2
Go to Diagnostic System Check - Instrument Cluster
2
Install a scan tool.
Turn the ignition ON, with the engine OFF.
With the scan tool, perform the Lamp and Gauge Check in the IPC Special Functions list.
Does the engine coolant temperature gage move up and down when commanded?
Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
Go to Step 3
3
Replace the IPC. Refer to Instrument Cluster Replacement .
Did you complete the replacement?
Go to Step 4
--
4
Operate the system in order to verify the repair.
Did you correct the condition?
System OK
Go to Step 2
Would hate for you to replace the coolant temp sensor an find out that's not the problem ! Does the vehicle start an run good ,trans mission shift good ? If so it's not the coolant temp sensor .
Engine Coolant Temperature Gage
The ECM sends coolant temperature as determined by the coolant temperature sensor to the BCM via CAN serial data. The IPC displays the engine coolant temperature with the gage when the BCM sends a class 2 message to the IPC indicating coolant temperature percentage. The engine coolant temperature gage defaults to cold (0°) or below if:
• The ECM detects a malfunction in the engine coolant temperature sensor circuit.
• The IPC detects a loss of class 2 communications with the BCM.
• The BCM detects a loss of CAN communications with the ECM.

The temperature gauge sensor as you call is for more then just the temperature gauge . The temp. sensor is an input to the PCM -engine computer ! If it were bad you would have drivability problems , the transmission would not shift correctly an the check engine light would more then likely be lit .
Engine Coolant Temperature Gage
The IPC displays the engine coolant temperature as determined by the PCM. The body control module (BCM) receives a class 2 message from the PCM indicating the engine coolant temperature. The BCM converts the engine coolant temperature into a percent gage deflection. The IPC receives a message from the BCM via the serial peripheral interface (SPI) indicating the requested gage position. The engine coolant temperature gage defaults to 38?°C (100?°F) or below if:
?€¢
The PCM detects a malfunction in the engine coolant temperature sensor circuit.

?€¢
The BCM detects a loss of class 2 communications with the PCM.

?€¢
The IPC detects a loss of SPI communications with the BCM.

Your gauge is more suspect then the sensor . gm had a problem with stepper motors that control the pointer for the gauge !

Follow the upper rad hose to the thermostat housing. It will be there. There are two, one is the ECT (engine coolant temperature SENSOR) and the other is the temperature SENDING UNIT (input for temp. gauge ONLY).

The coolant temperature sensor is a thermistor mounted in the engine coolant stream. A thermistor is an electrical device that varies its resistance in relation to changes in temperature.

For 2.5L engines, the coolant temperature sensor is located on the left side of the cylinder head.

For MFI engines, the coolant temperature sensor is located on the intake manifold water jacket or near (or on) the thermostat housing.



Fig. 1: Engine Coolant Temperature (ECT) sensor and connector




Fig.: Engine Coolant Temperature (ECT) sensor location-3.1L (VIN T) engine shown

Hope this helps (remember to rating this and leave an testimonial comment about this free answer).

According to Autozone.com:

Because ECT (engine coolant temperature) sensor procedures vary depending upon their location, first locate the part. You may need to partially drain the engine coolant to prevent coolant spillage.

• Disconnect the negative battery cable.
• Unplug the ECT.
• Then, unscrew it.
• Reverse the removal procedures to install the new part.
• Connect the negative battery cable to the battery.

Related Parts:



Cooling Fan Switch
Content for class "spacer" Goes Here

Engine Temperature Sensor
Content for class "spacer" Goes Here

Temperature Switch
Content for class "spacer" Goes Here

---
Coolant Temperature Sensor

Fig. Remove the coolant temperature sensor
The coolant temperature gauge sensor is a temperature-variable resistor, or thermistor. As coolant temperature increases, the resistance of the sensor decreases or decreases, depending on the type of sensor.
A1 and A2 platforms use a different type of circuit that A3 vehicles. On A1 and A2 vehicles, the circuit is a "resistance to ground" type. A3 vehicles use a "variable voltage" type, where a voltage is supplied to the sensor. Because of the circuitry design on A3 vehicles, testing of the coolant temperature gauge is limited.
The engine coolant temperature gauge uses a heat sensitive sending unit to transmit an electrical signal to the gauge. The sending unit is a heat sensitive variable resistor that is located on or near to the cylinder head and threads into an engine coolant passage. The sensors are a Negative Temperature Coefficient (NTC) type. As the temperature increases, the electrical resistance of the sensor decreases. As the coolant temperature changes, so does the resistance of the sensor. The gauge is calibrated within the operating range of the sensor and interprets the resistance value to display the coolant temperature.
Beginning with model year 1994, the engine coolant gauge and the Engine Control Module (ECM) temperature sensors were combined into one sensor with 4 terminals. The basic operation remains the same in that their resistance decreases as the coolant temperature increases, however the actual resistance values of the 2 sensor circuits are different. The electrical connector of the 4-wire terminal sensor ( 1 and 2 ) is keyed to prevent improper connection of the sensor's electrical circuit.

Fig. Beginning with model year 1994, the Engine Coolant Temperature Sensors combined the sensors for the ECM and the gauge into one sensor-1997 2.8L V6 sensor shown

Fig. The electrical connector for the combined temperature sensors is keyed to avoid improperly connecting the sensor's wiring-1997 2.8L V6 connector shown

Best Manuals I suggest you try one of those instant download manuals. My nephew bought one for me when my car broke and we could fix it all by ourselves with the manual costing $10. This website reliable-store.com is very good for this.
Try it.

VW Passat & Audi A4 1990-2000

Motronic System
The Engine Coolant Temperature (ECT) sensor is mounted in the water outlet on the back side of the head. If you vehicle still has a original VW part it will be black in color with a four terminal connector. This device signals the engine management system with the current coolant temperature, the ECU takes this information and uses it to control other such circuits as the idle speed, knock control system, oxygen sensor circuit, exhaust gas recalculation, and fuel tank venting. It is also important to note that if at any time ECU does not receive a signal from the ECT it will substitute a value of 176°F (80°C).

VR6
The Engine Coolant Temperature sensor is mounted in the thermostat housing. The body of the sensor will be blue and the sensor will be blue and have two terminals if it is an original factory VW part.

The engine coolant temperature gauge uses a heat sensitive sending unit to transmit an electrical signal to the gauge. The sending unit is a heat sensitive variable resistor that is located on or near to the cylinder head and threads into an engine coolant passage. The sensors are a Negative Temperature Coefficient (NTC) type. As the temperature increases, the electrical resistance of the sensor decreases. As the coolant temperature changes, so does the resistance of the sensor. The gauge is calibrated within the operating range of the sensor and interprets the resistance value to display the coolant temperature.On models produced prior to 1994, the engine coolant gauge temperature sensor is a single wire terminal sensor.

Beginning with model year 1994, the engine coolant gauge and the Engine Control Module (ECM) temperature sensors were combined into one sensor with 4 terminals. The basic operation remains the same in that their resistance decreases as the coolant temperature increases, however the actual resistance values of the 2 sensor circuits are different. The electrical connector of the 4-wire terminal sensor (1 and 2) is keyed to prevent improper connection of the sensor's electrical circuit.

WARNING When trouble shooting electrical components, always consult a wiring diagram for the particular year, make and model to ensure proper test equipment connection and diagnosis. Failure to use suitable test equipment and testing methods could permanently damage the electrical component(s).



Fig. Beginning with model year 1994, the Engine Coolant Temperature Sensors combined the sensors for the ECM and the gauge into one sensor-1997 2.8L V6 sensor shown




Fig. The electrical connector for the combined temperature sensors is keyed to avoid improperly connecting the sensor's wiring-1997 2.8L V6 connector shown

I hope help you with this, good luck (remember rated this help).

1994 Ford Truck E150 1/2 ton Van 5.8L MFI 8cyl Temperature Switch is located: Front seating area, center, under engine cover, front driver side of intake manifold, mounted in engine block.

The ECT sensor (Engine Coolant Temperature Sensor) is located either in the heater supply tube at the rear of the engine, or in the lower intake manifold. The ECT sensor is a thermistor (changes resistance as temperature changes). The sensor detects the temperature of engine coolant and provides a corresponding signal to the PCM. From this signal, the PCM will modify the air/fuel ratio (mixture), idle speed, spark advance, EGR and canister purge control. When the engine coolant is cold, the ECT sensor signal causes the PCM to provide enrichment to the air/fuel ratio for good cold drive-away; as engine coolant warms up, the voltage will drop.



Engine component locations-1994 5.8L engines

I hope help you with this, good luck (remember rated this help).

The Engine Coolant Temperature (ECT) sensor is mounted in the intake manifold and sends engine temperature information to the ECM. The ECM supplies 5 volts to the coolant temperature sensor circuit. The sensor is a thermistor which changes internal resistance as temperature changes. When the sensor is cold (internal resistance high), the ECM monitors a high signal voltage which it interprets as a cold engine. As the sensor warms (internal resistance low), the ECM monitors a low signal voltage which it interprets as warm engine.
Fig. 1: View of the Engine Coolant Temperature (ECT) sensor Fig. 2: Engine Coolant Temperature (ECT) sensor locationTESTING
See Figures 3 and 4

1. Remove the ECT sensor from the vehicle.
2. Immerse the tip of the sensor in container of water.
3. Connect a digital ohmmeter to the two terminals of the sensor.
4. Using a calibrated thermometer, compare the resistance of the sensor to the temperature of the water. Refer to the engine coolant sensor temperature vs. resistance illustration.
5. Repeat the test at two other temperature points, heating or cooling the water as necessary.
6. If the sensor does not meet specification, it must be replaced.

Fig. 3: Intake Air Temperature (IAT) and Engine Coolant Temperature (ECT) sensor wiring diagram Fig. 4: ECT sensor temperature vs. resistance values