NOX11 Sensor
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OXIDES OF NITROGREN (NOx) CONVERTING CATALYST MONITORING
Selective Catalyst Reduction Catalyst Efficiency Monitor
The SCR catalyst is monitored to ensure it is capable of NOx conversion. NOx concentrations upstream and
downstream of the SCR are measured with NOx sensors. Using these concentrations, the cumulative efficiency of
the SCR catalyst is calculated and compared to a threshold. If the cumulative efficiency is below this threshold at
the end of the sample period (approx 1 minute), a fault will be indicated.
The reductant, Diesel Exhaust Fluid (DEF), which is used as part of the SCR catalyst reaction, is monitored to
ensure the tank is not refilled with an improper reductant. After the SCR Catalyst Efficiency Monitor has completed
and the SCR has been determined to be functional, the efficiency monitor continues to calculate the cumulative
efficiency of the system, with a calibrated wait time between iterations of the monitor. Successive values for
cumulative efficiency are included in two filtering routines, one for short term efficiency and the other for long term
efficiency. The short term efficiency must be less than a threshold (0.35-0.55, depending on application) and the
difference between short and long term conversion efficiency must be greater than a threshold (0.10).
Selective Catalyst Reduction Catalyst Efficiency Monitor
The SCR catalyst is monitored to ensure it is capable of NOx conversion. NOx concentrations upstream and
downstream of the SCR are measured with NOx sensors. Using these concentrations, the cumulative efficiency of
the SCR catalyst is calculated and compared to a threshold. If the cumulative efficiency is below this threshold at
the end of the sample period (approx 1 minute), a fault will be indicated.
The reductant, Diesel Exhaust Fluid (DEF), which is used as part of the SCR catalyst reaction, is monitored to
ensure the tank is not refilled with an improper reductant. After the SCR Catalyst Efficiency Monitor has completed
and the SCR has been determined to be functional, the efficiency monitor continues to calculate the cumulative
efficiency of the system, with a calibrated wait time between iterations of the monitor. Successive values for
cumulative efficiency are included in two filtering routines, one for short term efficiency and the other for long term
efficiency. The short term efficiency must be less than a threshold (0.35-0.55, depending on application) and the
difference between short and long term conversion efficiency must be greater than a threshold (0.10).
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Rubicante
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
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04-20-2000 08:52 PM