1994 GMC k1500 4.3L temperature gauge issues

Salladself · April 13, 2021

Good day everyone, I’ve got a 94 gmc k1500 4x4 with the 4.3L v6. I’m getting zero reading on my dash for coolant temperature, while the other gauges work fine.

I have replaced the coolant temperature sensor ( up by the thermostat) and still nothing. Any ideas from any GM gurus? Should I possibly reset battery and see? Or can someone help me troubleshoot this? Any tips help!

any input would be appreciated.

and yes, I have read other posts regarding this but haven’t found what seems to be 100% accurate to my specific rig, thanks!

Edited April 13, 2021 by Salladself

thx1138v2 · April 14, 2021

There are 2 temperature sensors: the one by the thermostat and there is another one on the driver's side that is either in the block or the head. The latter one is the one that runs the gauge. The one by the thermostat goes to the computer to control fuel flow through the injectors when cold and then lean it out when the engine comes up to temperature.

You need to replace the one on the driver's side. That's the one that controls the gauge. I personally had fits trying to find one that would run the gauge correctly. I ended up finding one that is close and then adjusting the pointer on the gauge so it showed the correct position on the gauge when the engine was at full temperature. I used a non-contact thermometer to measure the temperature at the thermostat and then adjusted the pointer to point to 195 degrees. That's what my '94 4.3L C1500 runs at. I don't know if the K1500 is different. You can judge it by the thermostat.

All of the sensors I found had the correct physical attributes (size, thread, depth, etc) but the electrical properties were off. The sensor resistance works on a non-linear curve and I never found the right one.

Salladself · April 14, 2021

6 minutes ago, thx1138v2 said:

There are 2 temperature sensors: the one by the thermostat and there is another one on the driver's side that is either in the block or the head. The latter one is the one that runs the gauge. The one by the thermostat goes to the computer to control fuel flow through the injectors when cold and then lean it out when the engine comes up to temperature.

You need to replace the one on the driver's side. That's the one that controls the gauge. I personally had fits trying to find one that would run the gauge correctly. I ended up finding one that is close and then adjusting the pointer on the gauge so it showed the correct position on the gauge when the engine was at full temperature. I used a non-contact thermometer to measure the temperature at the thermostat and then adjusted the pointer to point to 195 degrees. That's what my '94 4.3L C1500 runs at. I don't know if the K1500 is different. You can judge it by the thermostat.

All of the sensors I found had the correct physical attributes (size, thread, depth, etc) but the electrical properties were off. The sensor resistance works on a non-linear curve and I never found the right one.

Thanks for the response! I replaced the sensor on the driver side head that is between the cylinders, but I was informed that is a knock sensor? That’s where I’m getting confused, does anyone have a picture of the area for the sensor?

I added a picture of the sensor I replaced, again was informed it was a knock sensor.

what am I missing? Haha.

Salladself · April 14, 2021

If anyone else has input on this I’d definitely appreciate it!

thx1138v2 · April 14, 2021

I just looked at mine and I have 2 sensors in that location, one above the other. It looks like yours has a plug in the head above your knock sensor. That's where the temperature gauge sender would go. I also notice a connector behind the ignition wires. That's probably the connector for it. Be sure to check that connector because I think there were single and double wire connectors and you'll need to know which one to get.

When you take that plug out, it is going to leak coolant so be ready with the temperature sensor to go back in so you don't spill too much. You might also want to pull the ignition wire there so it will be out of the way while you are dealing with it.

I don't know if this is the difference between the C1500 and the K1500 but it doesn't seem likely.

Salladself · April 14, 2021

2 hours ago, thx1138v2 said:

I just looked at mine and I have 2 sensors in that location, one above the other. It looks like yours has a plug in the head above your knock sensor. That's where the temperature gauge sender would go. I also notice a connector behind the ignition wires. That's probably the connector for it. Be sure to check that connector because I think there were single and double wire connectors and you'll need to know which one to get.

When you take that plug out, it is going to leak coolant so be ready with the temperature sensor to go back in so you don't spill too much. You might also want to pull the ignition wire there so it will be out of the way while you are dealing with it.

I don't know if this is the difference between the C1500 and the K1500 but it doesn't seem likely.

Again really appreciate the information. Does anyone by chance know the part#? I’ve tried asking at the local parts store about that sensor and they all seem to have no idea what I’m talking about, which I find strange. All they seem to have it the one that’s on top of the motor.

thx1138v2 · April 15, 2021

There are lots of part #'s as it changed at several points in time. The one I think you need is ACDelco 21377. But don't be surprised if it isn't accurate. See my note in the post above. As noted, I changed the pointer on my gauge so it points to ~195F when the coolant is hot. I would rather it be accurate at the point where it should be rather than off all the time and having to take the reading and add/subtract some number to get the correct reading.

The following link will show you several versions of the two sensor/senders: https://www.rockauto.com/en/catalog/gmc,1994,k1500+pickup,4.3l+v6,1157981,cooling+system,temperature+sender+/+sensor,4748

Look at the photos and see which one matches the connector you have.

BTW, the word "sensor" is usually used with the one that connects to the ECM and the word "sender" is usually used with the one that connects to the gauge. But it's not consistent.

Salladself · April 15, 2021

2 hours ago, thx1138v2 said:

There are lots of part #'s as it changed at several points in time. The one I think you need is ACDelco 21377. But don't be surprised if it isn't accurate. See my note in the post above. As noted, I changed the pointer on my gauge so it points to ~195F when the coolant is hot. I would rather it be accurate at the point where it should be rather than off all the time and having to take the reading and add/subtract some number to get the correct reading.

The following link will show you several versions of the two sensor/senders: https://www.rockauto.com/en/catalog/gmc,1994,k1500+pickup,4.3l+v6,1157981,cooling+system,temperature+sender+/+sensor,4748

Look at the photos and see which one matches the connector you have.

BTW, the word "sensor" is usually used with the one that connects to the ECM and the word "sender" is usually used with the one that connects to the gauge. But it's not consistent.

Thanks again for the response my man. I found the correct sensor and it definitely fits the connector. Sorry to play 21 questions, but what do I need to remove that engine plug? Looks like some sort of bit, but I honestly cannot tell for sure. I only have a small amount of tools, and very few bits and none of them seemed remotely close to fitting in there. Do you or anyone else by chance know what size bit I need to remove it? Sorry, don't have the money to be buying more tools currently and would prefer to just go buy 1 that will fit properly.

thx1138v2 · April 15, 2021

8 hours ago, Salladself said:

Thanks again for the response my man. I found the correct sensor and it definitely fits the connector. Sorry to play 21 questions, but what do I need to remove that engine plug? Looks like some sort of bit, but I honestly cannot tell for sure. I only have a small amount of tools, and very few bits and none of them seemed remotely close to fitting in there. Do you or anyone else by chance know what size bit I need to remove it? Sorry, don't have the money to be buying more tools currently and would prefer to just go buy 1 that will fit properly.

I don't know about the plug. Mine has two sensor/senders so I've never seen the plug.

thx1138v2 · April 16, 2021

On 4/14/2021 at 10:10 PM, Salladself said:

Thanks again for the response my man. I found the correct sensor and it definitely fits the connector. Sorry to play 21 questions, but what do I need to remove that engine plug? Looks like some sort of bit, but I honestly cannot tell for sure. I only have a small amount of tools, and very few bits and none of them seemed remotely close to fitting in there. Do you or anyone else by chance know what size bit I need to remove it? Sorry, don't have the money to be buying more tools currently and would prefer to just go buy 1 that will fit properly.

Some auto parts houses have loaner tools. You pay for the tool and they refund your payment when you return it.