2004 F-150 FX4
5.4
192k miles

I started having an issue with my temperature gauge spiking to full hot about 6 months ago. Checked all fluids and whatnot and it all was full and no leaks present. I initially started getting the gauge spike when the truck was over half throttle at low rpm's or under full throttle in a high gear. Basically, when under a load for any short period of time. After about 5-10 minutes of operation, the gauge would go back to normal and be fine.

Recently, I started getting the P1299 engine code and half cylinder drop as well as the temp-spiking gauge. Sometimes this is just sitting in traffic or under the aforementioned load. I could then turn the truck off and restart it and the gauge would go back to normal but the code and cylinder fail-safe would not go away until I cleared the code with a programmer.

Nothing is overheating to my knowledge and all fluid levels are good. Symptoms point to a bad sensor.

Is this correct? If so where is this sensor?

Thanks guys. I've seen lots of posts about this, but they all seem to go off on a tangent and other people posting their issues on top of them in the comment replies.

 

http://www.justanswer.com/ford/3vga5...tive-ford.html