Midbed Ammonia Sensor

[kozakvod]

Engine: 2013 ISX15 CM2350
Milage: 550,000

Issue #1:

After getting a 3165 fault code, I was able to get the truck to Lubbock where I met up with SnailExpress. He connected his Insite to my truck and found that the 'Final' temp sensor on the SCR was the one that threw that code because it had read a temp that was higher than allowed maximum. And actually at the time it issued the code it was reading a higher temp than any other temp sensor in the after-treatment chain. Sergye had a possible theory as to why it did that, but obviously no concrete proof.

Is there anyone else with an idea?

Issue #2:

See attached image. The 'Midbed' ammonia sensor stating "Reading not stable."

When we ran a forced regen this was the reading we initially saw. However, as the temps increased and during the majority of the regen that reading for that sensor went to "Reading stable." And as the temps finally cooled back down after regen was complete, the reading went back to "Reading not stable."

For what it's worth, the truck performed almost perfectly during the regen. No hiccups what-so-ever. All readings were good, temps good, everything performing as spec'd.

Anyone have any idea what's going on with that Midbed Ammonia Sensor to give that sort of reading when cool and yet when hot reading correctly?