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Engine Coolant Temperature related sensors/switches
Topic Started: Sep 3 2017, 06:13 PM (492 Views)
freegeo
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This post was originally posted by myredvert. Due to the photobucket issue the pictures were not viewable. I recovered the images and reposted his original posting.


Discussing or attempting to order any sensor or switch related to engine coolant temp can be frustrating, in part because the terminology can be "too" similar" sounding and create confusion. Also, the configurations and number of sensors used to perform the same engine functions based on engine coolant temperature changed over the model years.

GM databases seem to be the only consistently specific with respect to listing what the sensor does, although some parts diagrams still show configurations from previous years that don't show up in the individual listings/descriptions. Auto parts retailers such as Auto Zone, Rock Auto, etc seem to list more generic names and may even show different sensors under the same "name," in which case having the correct sensor in your hand in order to match up the actual picture can be very helpful.

When discussing a pre-95 sensor/switch, the words "Engine Coolant Temperature sensor" or "ECT" do not clearly indicate which sensor is being discussed as there are four separate sensors - two on the thermostat housing and two on the throttle body, all with very similar sounding names (except the radiator fan thermostat switch).

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95 was a "transition" year in which the sensor on the thermostat housing now fed the ECM (which controlled the radiator fan relay and AC shutoff during an overheat), but there was still a separate sensor for the gauge. On the 1.0L the coolant temperature sending unit for the gauge is on the lower right side of the intake manifold. On the 1.3L this sensor is in the thermostat housing next to the Engine Coolant Temperature sensor for the ECM.

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When OBD II systems began in 96, there was now only a single sensor that sends information to the PCM, which then uses it to control fuel scheduling, AC shutoff, and control of the radiator fan relay. These sensors also have a separate signal directly from the sensor to the gauge.

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Freegeo and I put these together using Factory Service manuals, GM expanded parts diagrams, and whenever possible, inspecting the actual vehicles and taking pictures of the various years/configurations.
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Woodie
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Thanks to myredvert for the original effort, thanks to freegeo for the fix.
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