I have also posted this in the HELP section. ok this morning the checkk engine light came on whike i was in the mountains I stopped and checked the codes with the key and got p 1693 which tells you nothing. I have relized over the last few day the temp has not been going up but i figured it was due to the cold as I am in Salt lake City and normally in San Diego. I went to Auto Zone and they put the code reader on and it said low coolant temp, I have changed out the T-stat but am supposed to drive 700 miles tommorow. I could use some suggestions, the truck seems to run fine and my fule milage is still somewhat normal.

 

An open thermostat would cause you low operating temps in winter time. I can't imagine this would hurt anything, not just get the engine up to operating temperature for the trip you have planned.

How is it since you changed out the thermostat?

 

It still has not registered on the dash but the heat works better. I am hoping it is only a bad sensor as i will be driving a long way tommorow.