coolant temp sensor. temp fluctuates randomly while driving.

[colinatorrr1]

I am new to this website and also my truck. its 2014 ram 1500 ecodiesel. the vehicle was passed down to my from my grandfather who can't drive anymore. I am very fortunate to have received this truck. the truck sat in his garage for a long time and only has 16K miles. I had to put a new battery in it to get it started up and get it to my house. I don't think he did any maintenance to it since he bought it brand new. first thing I did was change the oil and filter, put a new air filter and topped off the coolant. it ran great until recently. we took it on a vacation trip and had no problems but when we got back about a week later, the check engine light came on and was getting a service electronic throttle message. researched that and cleaned that all up. the CEL was still on. had it coded and was getting a P0118 code the message says "engine coolant temperature sensor circuit high". noticed that when I drive it the coolant temp gauge will randomly drop and it will read anywhere from -10 degrees and kinda float around 20- 40 degrees and then randomly read normal temps. this keeps happening. I know the coolant is not getting that cold I live in phoenix Arizona(HOT) so im pretty sure it is the sensor. I have that on order and on its way. also while replacing the sensor I want to just drain all the coolant and add new coolant. I have already located the sensor and verified it is the correct sensor by unplugging it and checking the computer on the dash. any tips on draining the coolant and has anybody had any issues like this with this year truck(diesel)

 

[EcoDieselJolene]

I've got a '17 and it did have some random code issues and a legit code issue from my oil temp sensor.
The brain trust on this site implored me to check a wiring harness that's under the driver seat area, up against the chassis (easy to find from underneath). Mine was actually surprisingly loose and not mounted correctly (I'm guessing poor workmanship from a prior service). I tightened that up and haven't had any 'random' codes since.
I haven't changed my oil temp sensor yet, but it works, then doesn't - kind of like your coolant sensor.

Good luck, I hope it lasts you many good miles.

 

[colinatorrr1]

I've got a '17 and it did have some random code issues and a legit code issue from my oil temp sensor.
The brain trust on this site implored me to check a wiring harness that's under the driver seat area, up against the chassis (easy to find from underneath). Mine was actually surprisingly loose and not mounted correctly (I'm guessing poor workmanship from a prior service). I tightened that up and haven't had any 'random' codes since.
I haven't changed my oil temp sensor yet, but it works, then doesn't - kind of like your coolant sensor.

Good luck, I hope it lasts you many good miles.

Yep I tried to disconnect it and reconnected it and it didn’t change a thing. Sensor still fluctuated and truck ran like crap still. I just bought a new sensor and swapped it out. CEL turned off and all codes went away. Trucks been running great since then.

 

[EcoDieselJolene]

Awesome!

The oil temperature sensor doesn't effect the trucks performance, luckily. I need a longer, skinnier arm, and a second elbow to get to it, though.