2017 Lacrosse LGX ECT issue

[jordanh912]

I've posted here before about a temperature guage issue with fans on high all the time. I found out if the temperature is low enough, it will register that temp, but will turn the guage off until one resets the engine light, whether there is one on or not. Turned out my temp was low, even checked with my infrared gun and nothing is getting near warm enough. I changed the thermostat last night and refilled the coolant. Didn't bother changing the ECT sensor while I was there because I'd have to remove the fuel rail and I didn't want to (I'm sure this is karma). After I put it all back together and now I have the same issue of no guage and fans on full blast right away, before it was intermittent. I was thinking the sensor initially until I found it was still reading temperature. Now that it's all back together and running, there is now no signal from the ECT and is registering the typical -40°F when they fail or circuit open.
Before I go digging back in to change that sensor and hope it's all it was, is there anything in this process that would have made this happen? To get to the thermostat, you have to remove engine cover, intake manifold, air box, two little coolant tubes from the heads that go to the overflow tank, pull out the thermostat pipe and lift out the thermostat. Tedious, but not that complicated really. Something in this process (maybe an air bubble?) make this throw a P0118 ECT signal high voltage? I even checked to see if I pinched the wire to it and it was snug so I moved it around to give it more space but I couldn't see that being the case.
Luckily, the car should be drivable, I still need to test drive it though to be sure. But engine runs fine, but fuel trim is quite negative now of course, I just don't want to commute to work not knowing my temperature.
Also, after it running for 30+ minutes last night while filling coolant, I noticed the engine oil temp wasn't registering either. Could that be somehow linked? Or would the fans going on high keep the engine from warming even the oil? I'm lost. Anything helps. Thanks everyone.

 

[MDC58]

I've posted here before about a temperature guage issue with fans on high all the time. I found out if the temperature is low enough, it will register that temp, but will turn the guage off until one resets the engine light, whether there is one on or not. Turned out my temp was low, even checked with my infrared gun and nothing is getting near warm enough. I changed the thermostat last night and refilled the coolant. Didn't bother changing the ECT sensor while I was there because I'd have to remove the fuel rail and I didn't want to (I'm sure this is karma). After I put it all back together and now I have the same issue of no guage and fans on full blast right away, before it was intermittent. I was thinking the sensor initially until I found it was still reading temperature. Now that it's all back together and running, there is now no signal from the ECT and is registering the typical -40°F when they fail or circuit open.
Before I go digging back in to change that sensor and hope it's all it was, is there anything in this process that would have made this happen? To get to the thermostat, you have to remove engine cover, intake manifold, air box, two little coolant tubes from the heads that go to the overflow tank, pull out the thermostat pipe and lift out the thermostat. Tedious, but not that complicated really. Something in this process (maybe an air bubble?) make this throw a P0118 ECT signal high voltage? I even checked to see if I pinched the wire to it and it was snug so I moved it around to give it more space but I couldn't see that being the case.
Luckily, the car should be drivable, I still need to test drive it though to be sure. But engine runs fine, but fuel trim is quite negative now of course, I just don't want to commute to work not knowing my temperature.
Also, after it running for 30+ minutes last night while filling coolant, I noticed the engine oil temp wasn't registering either. Could that be somehow linked? Or would the fans going on high keep the engine from warming even the oil? I'm lost. Anything helps. Thanks everyone.

Hello,
Did you ever find out what was causing this issue ?