Engine oil temp sensor location

[Traceman]

I did the HPOP Non-Serviceable plug repair the other day. I got everything back together and the truck started but it ran real rough coughing and sputtering until I got in and hit the accelerator. I tried it a few more times and it finally smoothed out. I have drove it a couple hundred miles but in the mornings it runs rough each time and this morning it would not start.

The code I am getting is P0198 which is
EOT Circuit Out Of Range High..where is this circuit? I wonder if I missed plugging something back up. It is almost like the glow plugs are not working but I don't see how doing the HPOP repair would have hurt any of that. I had the batteries disconnected through the whole repair and cleared out the superchip program and relaoded it but still doing the same thing.

Any help would greatly appreciated.