I have a 2012 F-150 Platinum with the Ecoboost. I have 160K miles on it and have not had any issues until I towed a 6,000# camper. Up to 60MPH, no problems. Over 60MPH-70MPH, the temp gage will move to red, the big red warning light comes on and I ease off the gas. By the time I get to the side of the road, the temp is back to normal. This is a cycle that does not stop.
A Ford dealer checked it out, found nothing wrong, and had no recommendations of what to do. I have used a laser thermometer and jump out of the truck to check the heads after the temp goes to red and never get anything over 200 degrees. Coolant has never boiled out.
Anyone had a temp sensor/program module issue? I've read other threads similar to this, but haven't seen a good fix yet.
Anyone found a fix for this?

 

What octane fuel are you using? For towing, 92 octane is recommended by the owners manual.
Is your coolant level low? When was the last time that the coolant was tested/changed out?
Has the radiator been checked (bubbles) to see if there is a blown head gasket?
There are a lot of variables to consider.

 

I've run both 87 and 94 octane, no difference. Tow mode and not. Coolant replaced a month ago. Checked and approved by ford dealership this week. No idication of any problem when hooked up to diagnostic. No heat code, cylinder heat code, etc., even though the big red warning on the dash has displayed 10-15 times while towing. It has gone into the limp mode once.

 

Do you have a way to monitor the OBD port data? If so, there are couple different coolant PIDs you can monitor. I know one is for coolant temp and one is cylinder head temp, may be others as well. Not sure which one the gauge uses, but you might help rule out a gauge/cluster issue.

 

Did you have the problem before the coolant change?