What does the VJT sensor do in a F-350 diesel dually

not satisfied with the other answer? Itdoesnt have a VJT sensor.

I would be interested in the results of you going to the dealer and finding out what it was.

I called the Tech Rep again today and asked about the sensor. She said it was a VGT sensor and had something to do with the Turbo system. They were installing it today, so I'll check again tomorrow. Interesting side bar on this. I was pulling my camper when the truck died and the tow truck they sent out was about the same size as my truck even though they had been told what size truck I had. The tow truck operator managed to drop the rear crane on my hood and scratched it up some. After getting everything hooked up he decided his truck was too small to pull my truck so they had to call out a bigger tow truck. Bad day all the way around.

Variable-geometry turbocharger - instead of a blow off valve, this turbo has vanes that can be adjusted to control the speed. The pop could have been a intake hose coming loose.

The 6.7L engine is equipped with a variable geometry turbocharger. Depending on the vehicle there are two different turbochargers used. The turbocharger used on a wide box frame vehicle is a 2-stage sequential variable geometry turbocharger. The turbocharger used on a narrow cab/chassis vehicle is a single-stage variable geometry turbocharger. I had forgotten they still used the variable vane but only on cab and chassis. As far as I know no turbo vehicle comes from the factory with a blow off valve people add those for a cool sound it serves no purpose other than that a wastegate controls boost pressure.