A0101531928
NOx - Engine Out · Detroit Diesel
NOx sensors in the SCR system of diesel engines: measurement upstream and downstream of the catalyst, failure patterns and replacement checks
The NOx sensor measures the concentration of nitrogen oxides in the exhaust, usually at two positions: upstream of the SCR catalyst, where it assesses the raw emission level, and downstream, where it checks the conversion achieved by the injected reductant. The sensor supplies the aftertreatment control unit with the control variable for AdBlue dosing and reports whether the required limits are being met.
Measuring range, connector and communication protocol are matched to the relevant engine family and emission stage; older and newer software versions differ in their evaluation electronics, even though the sensor ceramic itself works in a similar way. The assignment list on this page comes from official US EPA certification documentation.
An aged or contaminated sensor produces fault codes from signal drift or loss of communication on the CAN bus, often followed by a power derate once the aftertreatment system can no longer monitor its own function; deposits from the exhaust stream or from incorrectly dosed reductant gradually alter the measurement signal.
Replacement is matched by part number rather than mounting position, since the upstream and downstream sensors can share the same housing but run different software; check the connector and the seal in the exhaust pipe for corrosion; a relearn or basic setting in the control unit is often required after replacement. Price and availability are not covered on this page.
Fits these engines (6)
| Detroit Diesel DD13 | Heavy-Duty-Straßenmotoren |
| Detroit Diesel DD15 | Heavy-Duty-Straßenmotoren |
| Detroit Diesel DD15AT | Heavy-Duty-Straßenmotoren |
| Detroit Diesel DD16 | Heavy-Duty-Straßenmotoren |
| Detroit Diesel DD5 | Heavy-Duty-Straßenmotoren |
| Detroit Diesel DD5 Bus | Heavy-Duty-Straßenmotoren |
Excludes price and availability — those come from the supplier.
