No, it is not plugged in. I changed the thermostat, housing, and gasket. when i got the housing off i noticed the sensor was there and didnt have a connector on it. I finished the thermo change and started looking, but i cant find it.

Which harness? if i cant find it or its damaged, how do i replace it.

I *think* it comes in with the harness that runs up the passenger side, for the injectors and such...... It's a two wire connector.....

So last night i check the harness that runs up the passenger side. There were 8 connector (not including the ECT connector). I opened the harness where it T's off from the main harness, and there were on 16 wires which colors matched up to the 8 visible connector. So there were no extra wires for a possible ECT connector. I checked the harness on the driver side, and there was no extra connector or even to exposed wires where the connector could have been possible cut or broken.

To my eyes and everything i tried yesterday it would seem this connector doesn't exist, but i know that it has to, I just can't seem to find it.

My uncle and I tried looking for the electrical blueprints of the car, but the ones we found did match up to what was on the car.

Checked my 96, and it does indeed come from the harness that runs up the passenger side. Of course, things changed for 98..... (one of the temp sensors went away.....) Don't suppose you have a second sensor in there, that IS plugged in? One would be next to the thermostat housing, the other would be near the outlet in the intake manifold for the heater hose. My 98 has the V-10, which is totally different. :D

First off, Thank you for your continued help!

Yes my truck has only one sensor. There is another senor, just behind the alternator, which i believe in the Intake Air Temp Senor, which does have a connector attached to it. The issue now is according to the schematics we found for the truck the color of the wires that were plugged into the IAT sensor match the colors for the ECT. But i have never moved that connector, and only just started having issues last week. And if it is in fact the ECT senosr, then where is the intake connector.

Apart from removing the harness going back all the way to the ECM/PCM, I dont knw where else to look for the missing connector.

I took a break from it yesterday to clear my head, i may check the harness on the driver just to rule it out.

Oh and FYI, my symptom is the temp gauge on the dash rest at 210 (halfway) and will rise to approx. 250 (just before the red). the back down then back up. no leaks no "real" overheating symptoms other than the gauge.

The IAT screws into the side of the intake. It protrudes into the plenum there, to read air temp. The second coolant temp sensor, screws into the manifold coolant crossover, near the outlet pipe for the heater hose.

Your symptoms sound more like an air pocket in the system than anything else, but, if that were actually the cause, once the thermostat cycled a couple times, it should stop doing that.... unless you are rather low on coolant.....

Since the gauge is actually doing something...... that implies the connector is plugged into something.

Anyone ever sort this out? I'm having the same issue. The plug and wires are straight up missing. The sensor appears to be broken but I can't hook up a new one without the plug and wires. The Heck!

What year is your truck? How long have you owned it? How many miles on it?

Wow, thanks for responding to this old thread! It's a 97 and I've owned it since 2015, so not forever. 170k miles. I've been having issues with it for a long time, intermittent, only during certain types of weather, etc. Finally after trying lots of other things I figured out that this sensor is not even plugged in. Everything I've read seems to suggest that this year will have both a sensor and a sender. The sensor is broken and lacking a wire/plug.

After a lot more time searching it looks to me that the entire bundle of wires (that probably should include the plug) is tucked under the compressor... I kinda don't think it should be there, like someone had put things back together and accidentally tucked the wires into the wrong spot. Maybe it's possible that the plug is lodged under there and impossible to reach or see. I guess I won't know unless I take off the compressor. It just really looks like the plug is totally gone and I can't imagine there being enough space under the compressor that it would be there. I guess I am wondering if anyone knows exactly where this plug normally is so I can get a lead... haha. Thanks for reading.

Yep, 97 should have two sensors. A one-wire for the gauge, and a two wire for the PCM. Two-wire sensor should be right next to the thermostat housing.

Pull the compressor, have a look at the harness there, see if there is a couple extra wires. :D

You can download the service manual for your truck from here. Wiring diagrams are in section 8W.

Welcome to DF! :D