My truck seems to run fine when driving around without a load but when I hook up a trailer and tow it gets up to 215-220 degrees or so. I can turn on the A/C and the fan kicks on and it cools down some. So I am thinking there is a faulty temperature sensor, because the fan does work when the A/C is on but not just because it is hot. Has this happened to anyone else?

 

Check your water pump...

 

There is a flash for cooling fan, might help your overheat problem. Read tsb attached

 

I can assume the water pump is not faulty here as the truck stays cool during normal driving, this getting hot only happens when towing around 12,000lbs. I am going to check into the reflash some more and also try to check the temp sender to see if it is faulty. That is where I hope the problem lies anyway due to the fan working when the A/C is turned on so I know the fan works when the A/C overrides and turns it on. It seems to be whatever controls it in the ECM or the temp sensor.
Any more ideas are welcome though.....
thanks guys

 

If the temp sensor was bad, then your gauge would be off also.

 

I had temps in the 215 to 220 range when I just using the XZT and pulling 13k up some steep grades in 100 degree heat with a/c. After topping the hill the temps would come back down. I have not driven in those conditions since and have had no problems.

 

Its only about 30-40 degrees here and pretty flat land. I didn't really think about the sensor and guage being the same, are you sure there is only one sensor? I will have to look thru my service manual more closely. I just quickly skimmed thru the electronic diagnosis book because most of those tests require an OBD-III tool that I do not have.