Coolant temperature gauge not working?

Hello,

It sounds like the coolant sensor has shorted but to be sure lets run the codes this guide will help with instructions in the diagrams below to help you locate and replace the sensor.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Check out the diagrams (Below). Please let us know what you find. We are interested to see what it is.

Hi Adrian,

I just need to clarify what you are saying. You said the temperature gauge stops working. Are you referring to the engine temperature (coolant temp) or the outside or ambient temperature is not working.

I am providing material based on the second (ambient temp) is not working because this would be related to the AC not working at the same time. The HVAC module uses ambient or the outside air temp to determine AC operation. Again, I am assuming when you say the AC does not work, you mean it is blowing hot air. If this is all true, then when the ambient temp sensor is not working it defaults to -40 degrees. So if the HVAC module thinks it is -40 outside then it is not going to allow your AC to blow cold air. Since you already replaced the temperature sensor, then it could be wiring or the cluster, or even the HVAC module.

You said the check engine light is on so before we go much further I would suggest you have the diagnostic trouble codes pulled and reply to this message with those. Because based on those, this entire post could be correct or way off.

Let me know when you get the DTCs pulled and what they are and we will go from there. Thanks

Check out the diagrams (Below). Please let us know what you find. We are interested to see what it is.

Kenny

Okay. I see the check engine light is on. Do you know what the DTCs are when this happens? I see you said you would try to pull that so hopefully that will shed some light on this.

Also, when you say the AC does not work, what actually happens? Does it just blow warm air or does it not do anything when you turn on the HVAC system? Or does it not even allow you to turn it on?

It looks like the temp gauge that is not working only has the PCM related to the HVAC system. The PCM sends the engine temp to the cluster via a message data bus which means the cluster is just displaying what it is told to by the PCM. The PCM also can disable the HVAC if needed so I am starting to think the PCM is the common thing here.

I just want to make sure we have a little more to go on before you replace a module like that because they are not the cheapest thing. Let me know what codes you find and we can go from there. Thanks

Thanks. I think the DTCs will shed some much needed light on this for us. It is possible that the PCM is shutting down the compressor when the temperature gauge drops as a protection response because if it doesn't get an engine temperature feed, the compressor may add a load to the engine that will cause an overheat. Again, any codes should point us in the right direction.

Okay. That confirms basically what I was saying. The -40 is a default when the temp sensor/wiring/ECM has an issue with the engine coolant temperature sensor circuit. This DTC is saying the engine coolant temperature sensor (ECT) has a circuit issue. Basically, they are saying the same thing. If you already replaced the engine coolant temp sensor, then your issue is either wiring or an ECM.

I attached the test for this DTC. Let's fix this and I bet the AC not working will be fixed as well since I think that is the ECM shutting down the compressor because if it is truly -40 then the compressor will be damaged if it turns on. Check out the diagrams (Below). Please let us know what you find.