2006 379 Pete w/cm870 ISX.

[Peashooter67]

I found this mystery ambient air temp sensor and found it by accident.
In insite the ambient air temp sensor is actually your egr temp sensor or at least I think it is.

It was reading erratically for a while causing derates and high egt and then one day shortly after my query here it just quit and put out three dashes. This week end I got really tired of running incercles with no resolution from anywhere and just start unplugging every wire plug I could find.

Wow

When I unplugged the egt temp sensor all the sudden the ambient air temp sensor started showing a reading of 72* constant with no change. Plug it back in - - -, unplug it 72* and my full throttle derate went away.