Ford knox sensor

It was most likely a Nox sensor. Mine failed at around 110k miles and I don’t run additives.

ACZL, if it is a NOx sensor that your are referring to then yes aftermarket fuel additives could be the culprit. NOx is created when in cylinder temps get above 2,800F which a diesel engine normally does. To combat this, two things may happen. One, the EGR valve will open introducing cooled exhaust gas back into the intake to cool the in cylinder temps down. Two, if the SCR catalyst is hot enough, the system will inject more DEF if the NOx sensors detect more NOx downstream from the DPF.

You have NOx sensors at various parts in the exhaust/emissions system, and a fuel additive may alter NOx level. So basically what is happening is the ECM is triggering the EGR and SCR to combat the NOx being created, but the fuel additive may be making the engine run more efficient creating more NOx(yeah, an oxymoron). This will trigger a CEL because the engine is doing what it is programmed to in order to reduce NOx, but the amount is still not coming down to normal levels due to the fuel additive.

NOx and emissions devices is the real reason why diesel makes don't recommend additives anymore even though they want the best fuel possible ran through their engine and they do make them run more efficiently. If they recommend a fuel additive that increased NOx output or damages emissions equipment, then they could be liable.

The are knock sensors and a NOx sensors. Which one are you referring too? I am guessing since it is a diesel in your sig that you are referring to the NOx sensor.

DownTheAvenue wrote:
Stop using the aftermarket fuel additives. You are told why your check engine light comes on. Diesel fuel already is formulated to prevent gelling right out of the pump. Isn't science amazing?

Try telling that to folks in areas where temps get down to -30 to -20.

mleekamp wrote:
....and by the way, it's a Knock Sensor, not Knox

That's what's printed on repair order and it's related to emission system so IMO I really think it's supposed to be nox , but again that's what's written down on paper I was given.

....and by the way, it's a Knock Sensor, not Knox

Stop using the aftermarket fuel additives. You are told why your check engine light comes on. Diesel fuel already is formulated to prevent gelling right out of the pump. Isn't science amazing?