01-05-2017,
There are 2 nox sensors, considered to be "outlet" sensors.
The NOX sensor right behind the turbo is the engine outlet NOX sensor. The emissions system outlet nox sensor is after the SCR can in the exahsut.
Here is some interesting video that is related, though it does not show the sensors.
https://youtu.be/p8clK9qSGlk
I have seen many trucks throw emissions system outlet nox sensor alarms. Those nox sensors have a short lifespan and read wrong after about 200k miles or so typically. Also, the older your DOC can gets, the more likely you will get outlet nox sensor alarms. I have seen Chinese fake DOC's installed on trucks too, and give constant outlet nox sensor complaints. As well, bad DEF fluid will do it, cloghged decomp tube will do it, problems with DEF doser injector or supply will do it, clogged DEF doser screen filter, etc.etc.
The NOX sensor right behind the turbo is the engine outlet NOX sensor. The emissions system outlet nox sensor is after the SCR can in the exahsut.
Here is some interesting video that is related, though it does not show the sensors.
https://youtu.be/p8clK9qSGlk
I have seen many trucks throw emissions system outlet nox sensor alarms. Those nox sensors have a short lifespan and read wrong after about 200k miles or so typically. Also, the older your DOC can gets, the more likely you will get outlet nox sensor alarms. I have seen Chinese fake DOC's installed on trucks too, and give constant outlet nox sensor complaints. As well, bad DEF fluid will do it, cloghged decomp tube will do it, problems with DEF doser injector or supply will do it, clogged DEF doser screen filter, etc.etc.