From another forum...

[Rawze]

(09-25-2021 )marek4792 Wrote:  I must be the lucky one then, in a Volvo of all trucks..

Every red ISX engine that I have seen so far, ... the exhaust temp data from the engine ecm is totally estimated, and not actually measured. It is also highly inaccurate, prone to spiking between gear shifts erroneously, and mostly useless.

So if you have a factory EGT gauge in the dash, it is more likely to be either the truck makers gauge and sensor .. or a gauge reading the garbage EGT estimation signal from the ecm?.

Either way, it makes someone question its actual source of input.

What is your engine ser#? .. and what program is in the engine?. ... Maybe a pic of the EGT sensor itself that would be located right after the turbo?? and mounted next to the engine out NOx sensor?.