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Hey Joe, What the @#$% is a NOx Sensor?

Playing a critical role in your after treatment system, the NOx Sensor is a high temperature device designed to measure both the oxygen and NOx levels in your exhaust. Most common after treatment systems will have two NOx sensors: One "upstream" on the turbo side of your Particulate Filter (DPF) and the second "downstream," on the outlet side of your Catalyst (DOC). The two signals, sent directly to your ECM, are then compared to determine the “conversion efficiency” of your exhaust system.

It's usually a good idea when changing out your DPF and/or DOC to swap out your NOx sensors as well, which can add significant cost, but will ensure smooth operation of an already complex system. This can be a bitter pill when you’re putting down several thousand for a new DPF or DOC, which begs the question, why are they so darned expensive?

Similar in design to your standard Oxygen sensor, the NOx sensor has a dual chamber design that measures both Oxygen and NOx content. As exhaust enters the sensor the Oxygen is pumped out and the NOx finds its way to a second chamber where the gas is exposed to a catalyst that calculates and reports that information to your computer. It’s complex stuff, which helps to explain their price tag.

As the online leader in after treatment systems, BIG Machine Parts offers quality manufactured and lab tested aftermarket NOx sensor options fitting Cummins, Detroit Diesel, Volvo and Mack engines.

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