Not sure if this should be in here or non-drivetrain folder. Back in July this year, I got a low coolant warning on my 2018 3500. All looked good, no overheat. waring light has been on since. I picked up a new overflow bottle with new sensor. Finally got around to putting it in today. Warning went off for about 5 minutes then came back on. Okay, maybe system burped. Added a little more coolant to bottle. It is above the seam of the bottle (which is the 'min" level). Low coolant is still displayed on dash. I verified that the sensor was plugged in tight. I would not think so, but does the PCM need to be flashed to get rid of this? What else would keep this warning active? Guess there is always a possibility that the new sensor is bad, but ...

2018 RAM 3500 6.7L 144,000 miles

 

Time to trace the wires to see they chaffed against something and grounded out. Good Luck.

 

Thought I would post a follow up, in case anyone else has to replace a coolant sensor and/or coolant bottle. The Dorman bottle I got came with a new sensor in it. I do not know if the pins on the sensor were too small, too short, or if the design did not allow the plug to seat. If I wiggle the plug, the warning light would come and go. After some quick search of reviews, I went to Dodge dealer and got a MOPAR sensor. Problem fixed.

Go to the dealership and get a MOPAR sensor. They are not expensive. In fact, local NAPA wanted $26.95 for an aftermarket and I got one from the dealer for $22.85