Today, my coolant temp gauge stopped displaying numbers.

To my knowledge, it has never done this before. I rarely keep my DIC set to Engine temp, but with colder weather, I sometimes like to see when I'm warmed up. I shut it off and back on and it still displayed "---"
I never got a CEL, or other warning. Pic, https://db.tt/xIsHtEcJ


When I got to my destination, I checked the coolant level, and it's a bit low in the reservoir. Seeing that made me realize that the car hasn't been reaching 192° since I've been monitoring it for the past couple weeks.

Car has 100K miles on it, and has never had a coolant system service.

Thought would be appreciated, thanks.

 

Sensor probably bad

 

Also time for a coolant service. I do it every 75k since it's so cheap.

 

As far as I know, there are two things that can cause this. First is for the sensor to fail. Second is when the ECM detects that it is taking too long for the car to reach operating temperatures. This generally signifies a thermostat that is stuck open.

 

Or low on coolant? I could assume

 

More than likely a sensor. Best way to tell would be if you can see what the ECT sensor displays on a scan tool.

 

I've had that happen before, the coolant was so low it wasn't hitting the thermostat. Its pretty obvious if you are though, check to see if the reservoir is full. That was when I found out my headgasket was bad too.

 

Sensor is easy to change as a starting point. As mentioned, check your levels and it never hurts to put some fresh coolant in there, but if it's low you will get a low coolant message. Temps reading "---" is almost always a failed sensor.

 

Update: I got in my car to go home, and it still showed ---. However, I stopped at a gas station on the way home, and when I started again, it was back! For a split second, I saw a message flash on the display. No way to read it, it was so fast. But it may have been the low coolant message. I'm going to grab the pink stuff tomorrow.


Also, my gauges look HOT at night. https://db.tt/YIJ4wy0x

 

Should be orange coolant, not pink (pink is audi/VW G12, Dex-Cool GM stuff is red-orange)

 

Maybe it is orange. I saw what looked like a light reddish color. Hard to tell.

 

It's not uncommon for the coolant temp sensor to go, had to replace it on my mom's 2.2 cobalt at 60,000 miles along with a thermostat. The sensor is along the pipe on the back of the motor just behind the thermostat.

 

I had this happen last year, it was my thermostat that had to be replaced. It is really easy to do and only takes a few minutes. Every so often it would read a temp if the engine got hot enough but for the most part it was "---"

It's designed to get your attention, easy test is turn on your heater and see if it takes longer to heat up or if it seems cooler than usual.