On 10/14 I went on a short trip to a nearby campground towing my 10k travel trailer. I didn't have a problem going there, and honestly, my truck hasn't had a single problem since April when I bulletproofed it. The only codes currently present are a couple for 2 failed glow plugs and a U1900 for an issue I cannot remedy, but never does it influence anything. I have monitoring software and ways to monitor with alarms set for everything, to include coolant/oil deltas.

I was about 20 minutes into a 1.5 hour trip and the wrench light popped on. No reduction in power or anything, just a wrench light and P012F. It has a new oil cooler (installed in April) and has had a coolant filter on it since 2016 and has ELC coolant in it. I literally just changed the oil and filter last week with Rotella 15w40 dino and a motor craft filter.

What's peculiar to me is that my deltas were good. As in, really good at that time. Less than 8 degrees while towing. I pulled over, reset the PCM and restarted. No wrench light for the rest of the trip.

Could this have just been a fluke? I've never seen over 12 degrees difference between those temps. EVER.

 

Maybe a voltage spike/ dip in one of the sensors caused a high or low reading that your monitoring device wasn't fast enough to catch?

 

Biased sensor anomaly, or as Mark mentioned a spike/dip

Kids truck has #6 contribution code that just pops up randomly at times, even though the health of the injector checks out fine, and it never misses.
It's one of those reset it and forget it things.

 

You when your bored and looking for something to do other than house stuff or other things like Super Bowl on the TV
take a good look at the wiring harness to see how it is holding up around the temp sensors and the sections of harness
leading to both of the locations.

The U1900 could be from a bad termination on one of the network lines. I have a copy of OBD2 diagnostics but am not sure
where I saved it to. It was based on using a multimeter to help find the issue.

 

Towed my boat with it today (all 2100 lbs, of it) and had no problem. I'm convinced it was just a voltage spike or something.