Coolant temp reads 0 and SVC 4WD light on

[RAMLUVR69]

Hey guys, so this morning as I was driving (for the first time in a few days and first real cold day), I heard a chime and saw the SVC 4WD light came on as well as the temp gauge instantly dropped to full cold.

Heat was still working well and the truck still seemed to shift into 4WD, or at least the 4WD light illuminated solid when I tried.

I had the water pump and coolant temperature sensor replaced last year so I have trouble believing the sensor is at fault here. Any suggestions?

So my 2 questions are, Can the coolant temp gauge dropping to 0 trigger the SVC 4WD light to come on, or am I looking at an electrical gremlin? and, is it possible for an air bubble to form in the water pump, causing the sensor to not get a good reading if the coolant is low?

Thanks in advance for any help guys. Truck is a 2012 5.7 with 56 000 miles temp was -20c or -4f today

edit - Forgot to mention, when I arrived at my destination, I restarted the truck and all was normal, temp needle right in the middle where it should be, 2nd restart and trip home was fine aswell.

 

[Tach_tech]

If the service 4wd light came on there will be codes stored. Get those codes retrieved first. Could be any number of things, but knowing what code is set will help narrow down a direction.

 

[RAMLUVR69]

If the service 4wd light came on there will be codes stored. Get those codes retrieved first. Could be any number of things, but knowing what code is set will help narrow down a direction.

Finally had a chance to pull the code today P0116 "engine coolant temperature sensor"

Which is odd since I changed the sensor last winter after having an issue with the temp reading low causing a check engine light.

What worries me is how it dropped from operating temp to 0 in an instant, completely losing signal with the sensor. Makes me think a short or broken wire somewhere.

 

[Dodge 1500 4X4]

Is it a OEM sensor, sometimes after market sensors go bad.

 

[RAMLUVR69]

Is it a OEM sensor, sometimes after market sensors go bad.

I would hope its OEM as I got the dealer to replace the water pump and sensor last winter. Was too cold to do it in my driveway myself.

I cleaned the connector to the sensor at the water pump with some contact cleaner and so far no more issues. Time will tell, Thanks guys.