Locate engine temperature coolant sensor on jetta TDI 2004

Located in the side coolant flange on the cylinder head. When engine is cold, remove the retaining clip and remove the sensor and seal and replaced with new.

The exact locations and picture of Engine Coolant Temp (ECT) sensors on 2001 VW Jetta TDI:

1. ECT sensor 1 placed on cylinder head:





2. ECT sensor 2 placed on the left bottom side of the radiator:

COOLANT TEMPERATURE SENSOR THREADS INTO A COOLANT PIPE NEAR THE COOLANT OUTLET.LOOK AT SMALL COOLANT PIPES AT RADIATOR.YOU WILL SEE A SENSOR WITH WIRES CONNECTING TO IT.WITH COOLANT COOLANT HOSES CONNECTED TO IT.COOLANT TEMPERATURE SENSOR IS BETWEEN TWO COOLANT HOSES CANT MISS IT.YOU HAVE TO SQUEEZE CLAPS ON HOSES WITH PLIERS IN ORDER TO REMOVE HOSES FROM COOLANT SENSOR.

Replace bad Engine Coolant Temperature (ECT) sensor. ECT sensor is placed in the right back side of the cylinder head on 2002 VW Jetta 1.9 TDI. See picture below:

COOLANT TEMPERATURE SENSOR LOCATED COOLANT PIPE NEAR THE COOLANT OUT LET.

Replace the Engine Coolant Temperature (ECT) sensor. ECT sensor is placed in the right back side of the cylinder head on 2002 VW Jetta 1.9 TDI. See picture below:



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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
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Engine Temperature Sensor
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Temperature Switch
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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

The exact locations and picture of Engine Coolant Temp (ECT) sensors on 2004 VW Jetta TDI:

1. ECT sensor 1 placed on cylinder head:




2. ECT sensor 2 placed on the left bottom side of the radiator:

it should be near a coolant hose or your water pump

Yes it is that easy. It should be a 4 pin connector located on the transmission side of the engine head in a plastic flange. Best is to wait for the engine to be cold. Unscew the radiator cap to relieve pressure but screw it right back on. On the 2.0L engines when you unclip the coolant sensor little or not coolant loss will happen if you do this. Just unplug it, pull out the clip, pull out the sensor, and the seal which sometimes stays stuck. Install the new sensor with a new seal lubricated with some coolant, make sure it's well seated and reinstall the clip. The sensor is well seated if the clip fits right over the top, just make sure both sides clipped into position. Replug it fill the coolant with VW original coolant mixed 50-50 with water if needed and done. If you have a fault you might need a scanner to erase the check engine or fault in the cluster.

What's the reason for changing it? Eratic temperature readings?