Gotta be a flaky connection somewhere.

 

Im not seeing anything suspicious as far as connections. All the grounds are looking good, and the connector to the sensor is in nice shape. One thing I hate is electrical issues. Don't have all those fancy short finders.

 

Me either. Did you check the connections at the PCM?

 

yes, I'm going to spray some contact cleaner on them and also the temp sensor connector. Then let the car run a little more, maybe trapped air still. Just weird how this happened out of nowhere since I haven't had to do anything to the truck for a few years now. Drove it out of town to pick up a project car and as soon as I got home it started out of nowhere.

 

So I have checked all connections at the PCM and at the temp sender, cleaned them all with contact cleaner and reinstalled. I feel if it was a short or ground issue it would do it at all temps. On cold start up the live data shows it increasing like ECT data should, it only starts to act up once it gets into the 170F range, then it eventually does its massive fluctuation. The video below shows cold start temp change.

 

Here is a longer video showing that it still continues after I cleaned PCM and temp sensor connectors with Electronic contact cleaner, checked grounds, and let the truck warm up for 20 min. Seems to start acting up once temps get into the 170F range. I also show all the temps at the hoses while it is doing this. I may take the temp sensor back to Oreilly's in case it is defective. But im at a loss on what it may be given my ability.

 

New temp sensor and still doing the same BS

 

After continuous diagnosing, and having a pro look at it, it seems to be a PCM issue. Something is causing a voltage loss so Im going to look for a new PCM and have it flashed.

 

That's all that's left. I think you are correct. Might try attempting to cool the PCM as the engine temp reaches 170, and see if behavior changes. Just putting a fan on it would probably be adequate to the task.

 

You could hook up a meter to the return signal from the sensor and see if the voltage fluctuates.