Coolant temperature sensor?

Hello, I see what you mean, going through the wiring diagrams I've found a 2-wire sensor and a 4-wire sensor. I think one is for the computer, and the other type seems to be for the computer and for the gauge with a switch in it as well as a thermistor (sensor). Can you tell me the wire colors for the sensor on your car? The four wire colors on the harness plug. Some will be a solid color with a stripe down the side. I'm trying to find the correct sensor for you. There is either two coolant sensors for different reasons or there are two different designs. You can check the wiring with a multimeter if you'd like. I can walk you through it just to verify the wiring from the computer is okay.
If these 4 wire sensors colors are correct, solid yellow, solid purple, green with white stripe, and solid Dark Green (2nd diagram). Let me know.
And the third diagram, is that the sensor you are trying to replace?
One other thing, take a look at the tag on the inside of the door frame or on under side of the hood, there should be a build date, month and year (example 12/93 or 12/1993). It might be a change in design during the build year.

This is the OEM (Chevy) part number for the 4 wire Coolant Sensor/Switch (10137646). It might be something you could try calling a dealership and see if they carry this 4-wire sensor or if they know why there are different sensors listed. I will keep looking though.


This is a link to napa auto parts store. They have a 4-pin coolant sensor for $32.00. This looks like the correct sensor. This one has a switch for the coolant light, as well as a resistor for the gauge and another resistor for the engine computer input. Thats the difference between the 2 or 4 wire sensors. This could be a discrepancy due to where the car was built, the time of year it was built and possibly if the car is California emissions or not. But the link below will take you to the correct sensor, I don't know if you have a Napa near you, but you could order this online if needed.

https://www.napaonline.com/en/p/DEMTS10032?cid=paidsearch_shopping_dcoe_google&campaign=GSC-Fasteners-Hardware&campaign_id=10947735022&adgroup_id=107081865346&adtype=pla&gclid=CjwKCAjw4c-ZBhAEEiwAZ105RceXsb4vXwLsciPjh8TJC_zQezdM8GLpcEmZ-vL6uL6clr5lB3jzohoCuDMQAvD_BwE&gclsrc=aw.ds&

https://www.2carpros.com/articles/how-to-use-a-voltmeter

The 4 wire colors for the sensors plug are solid yellow, solid purple, solid dark green, and green with a white stripe. I also checked out the link for the sensor at Napa and it’s not the right sensor the plug is a different shape. The build date for my car is 12/92’.

I searched for the OEM part number you gave me, and I found sensors on eBay that seem to be the right fit for my plug. one is $35.00 that matches the same part number and one that also looks the same has a part number 213-55 and it was only $12.00.

Just found out that it was an Ac Delco part number, that’s why it’s different. I think I’ve found the right sensor thanks to you. Thank you so much you’ve been a great help. I hope you have an amazing day.

Okay, great. I recommend getting the part from an auto parts store if you can. eBay parts may not be the best quality. We've seen a trend in parts over the last few years and the quality has declined significantly. And a coolant sensor is an extremely important input into the ECM (engine computer). It's the main sensor the computer will look at for its fuel strategy. Especially at cold start ups. If you want to check the wiring let us know. If the light is still on or the gauge is not working, after you replace the sensor. You can check the wiring with a basic voltage multimeter. Make sure when filling the coolant after the sensor replacement to allow the car to run while cold with the radiator cap off for a few minutes to help get the air out of the system. Just open the coolant system in the morning before the car has been started for the day so you don't get burned by the coolant, I say this from experience when I was starting out. Hot coolant in the face is very unpleasant. Hope all goes well...

https://www.2carpros.com/articles/coolant-temperature-sensor-cts-replacement

When I search for this part at parts stores it says it’s discontinued.

https://www.ebay.com/itm/374096409777?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=dMQ31ADCSlq&sssrc=2349624&ssuid=algp08aptb-&var=&widget_ver=artemis&media=COPY

This is the link to the best online option. What do you think about this, if I’m not able to find it in a part store?

It is giving me a not compatible message for your car. I can understand why it would be discontinued. There' has been a lot of issues with getting parts for older vehicles as well as some newer ones. I'll search around a little bit more for you too. Check Rockauto com
Which part number did you find that was correct? And can you take a picture of the old sensor plug end? So, I know what the connector is going to look like.
Do you have a multimeter? Just a basic one?

The OEM part number you gave me was the part that I found is the correct one.

Okay, I'm having a lot of trouble finding it as well. Even trying a 1992, there just aren't any in stock anywhere. Do you have AutoZone or Advanced Auto in your area? You could try calling them and give them the OEM number, tell them it's a 4-wire sensor. Maybe they can order it. Or a dealership, maybe online. They have them in stock for the 1994, but they all look 2 wire.

Yeah, I’ve tried both of those. And earlier today I tried O'Reilly the guy working took my info and would call me back if he found something because I spiked an interest in trying to solve this.

This is the diagram from a 1992, do you have another sensor below like this picture?
Interestingly, this is the OEM part number for the 1992, 10137646- same number as the 93'. On the tag on the underside of the hood say 'California Emissions Standards?

No mine doesn’t have the second sensor below. Just has one.

If I take the sensor out will it have the part number on it?

In the description of that eBay part. They say it fits a 1992 and 1993 Corsica base and the LT.

No, I don't think there will be a part number on it, does the hood tag say California Emissions? The 1994 part number is different.
If you have a multimeter that can check resistance, we can check the sensor
I would check the connector too, to see if there's any corrosion on the pins or in the connector.

I took the sensor off of my car and I cleaned it the best I could with an old toothbrush. It does have a number on it, and it is the same part number you gave me. But there is a little green stuff on the pins and some thick sticky stuff.

No, it doesn’t say California emissions anywhere on it. It just says vehicle emission control information: General Motors corporation

After the part number on the sensor, there is a space then 3022.

The green stuff is not good, what does the inside of the connector look like? Look really close into the female pins with a flashlight. See if the corrosion got down into the wiring harness. That might be your whole problem. If there's green crusty on the sensor pins then 90% of the time there is down in the harness connector too.

Okay, I’ll do that right after I eat dinner. Thank you

Look in the back on the connector too, the green corrosion works its way down into the wiring under the insulation and keeps growing down the wire. You can't even see it most of the time. Thats why we do so many different types of wire testing..

If it’s corrosion that’s causing it to fail, would I only need to replace the wiring harness?

On the wiring harness only one of the female connectors is corroded. It’s the connector for the dark green wire.

I cleaned the corrosion off the sensor and off the wiring harness to the best of my ability and letting it dry really well before i put it back together. Fingers crossed.

I clean the corrosion off the sensor and off the wiring harness to the best of my ability and letting it dry real well before i put it back together. Fingers crossed

It depends on how far down inside the wiring insolation the corrosion goes. You can get terminal spray cleaner at an auto parts store and try that. But the Dark Green wire is only the ground wire for the Engine Temperature light. It will come on when the temperature gets too high to warn of overheating. I have that part of the sensor in orange below. The green/white wire is for the Gauge. As you can see it's a 2-part sensor. The other section goes to the engine computer to calculate the air/fuel mixture. With a multimeter you could test pin B to the housing of the sensor and see if there was any resistance reading on the Ohms setting. If the meter reads OL then the sensor has an open circuit inside. If there is a resistance reading, then there might be an issue with the wiring to the sensor going to the Instrument Cluster.
The corrosion causes high resistance in the circuit, and since this sensor works specifically on the resistance changing due to heat, this is why bad connections and corrosion cause big problems with this type of circuit.

Okay, that makes since. I don’t have a multimeter; I need to get one. But I’ll have take it to the part store to see if they can run a multimeter on it for me.

Okay. I was thinking, since you're having so much trouble finding this sensor, you could try a vehicle used parts yard, if you look around, I'm sure you could find one. I know in my area there are a bunch with wrecked cars, and you can just go take the sensor out yourself and they only charge a few dollars. It might not be new, but it won't be broken.

That’s a good idea. I might just do that. The sensor still doesn’t work after the cleaning. When the car is running, and I unplug the wiring harness from the sensor the fan kicks on and when it’s plugged in it turns off.

That might be a safety feature. The engine computer will sometimes turn the fans on when it doesn't know what the engine temperature is. This way it prevents overheating. That tells you that the coolant temperature part of the sensor that goes to the ECM is most likely working okay. Is you check engine light on?

I have a question about the motor. I noticed when I was leaning on the front of my car looking at the radiator hoses trying to burp the system because I think I may have an airlock, that the motor moves back and forth a lot when the car rolls back and forth. Would that be a motor mount problem you think?

Most likely. The motor mounts are mostly made of hard rubber. But they wear out like everything else. You should be able to see movement in the upper motor mounts if they are visible.
Are you hearing a gurgling inside the vehicle while driving? That makes you think theres air in the system? An easy way to get air out is in the morning when the vehicle is cold, open the radiator cap, top off the radiator, and leave it open, then start the car. It will bubble any extra air out. On these older vehicles, I used to leave the radiator cap off until the thermostat opened. You could tell because the coolant will drop way down. Then I would top it off again and close it up. Just do not open it if the vehicle has been run that day. Only do this when its stone cold..

I can’t seem to find anything on google about the motor mounts for my car. Closest thing was a 1991 Corsica. Do you think it has the same mounts?

No, I don’t hear any gurgling coming from in the car. But I filled the reservoir and it’s not draining into the radiator. But I did it how you said I open the reservoir cap and started the car and let it run until it got warm but it never drained into the system it stayed full and I tried to squeeze the hoses to burp it but it did nothing.

There are only two motor mounts that I can find online.

It's probably full then on coolant. Try turning the heat on too, if there is a diverter valve that is used for the heater core inside the vehicle, turning the heat on high will allow coolant to flow into the heater core inside the dashboard. I'll look up where all the motor mounts are if I can find them.

Yeah, I see a mount on the front of the engine, one on the rear, and there might be one underneath supporting the transmission.
Is the engine shaking a lot while it's just sitting and idling? With the hood open? Cylinder misfires will make an engine shake somewhat.

It has a loud shaking vibrate noise when idling in drive, but when I switch neutral it stops. When the car was in park and rolled it back and forth the engines moved significantly it seems.

It sounds like there are some cylinders that are misfiring. When you shift it into Drive, you're putting a load on the engine and that's when most misfires show themselves. If it smooths out as you start to drive and have your foot on the pedal and you're opening the throttle plates it might be a vacuum leak. But when it's in Neutral or Park, there's no load on the engine. Granted the motor mounts may be worn down. I check those when a vehicle is turned off. Using a pry bar I'll go around and put some pressure where the mounts are and see if the engine will move more than it should. Using a long pry bar gives you some leverage to really check for play and worn-out mounts.

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

https://www.2carpros.com/articles/how-a-motor-mount-works

https://www.2carpros.com/articles/replace-motor-mounts