Method and system for sensor analysis in an exhaust gas aftertreatment system

A computer implemented method for sensor analysis in an exhaust gas aftertreatment system (EATS), wherein:

• the EATS is coupled downstream of an internal combustion engine (ICE) and provided for treating exhaust gases from the ICE, and
• the EATS or the ICE comprises a processing unit,
• wherein the method comprises:
• dosing, under control of the processing unit, a first amount of a reductant into the exhaust gases at a first position upstream of a first nitrogen oxide (NOx) sensor comprised with the EATS when operating the ICE at a first constant flow of NOx,
• receiving, at the processing unit, a first set of measurement data from the first NOx sensor indicative of an amount of NOx in the exhaust gases at the position of the first NOx sensor,
• dosing, under control of the processing unit, a second amount of the reductant into the exhaust gases at the first position when operating the ICE at the first constant flow of NOx,
• receiving, at the processing unit, a second set of measurement data from the first NOx sensor indicative of an amount of NOx in the exhaust gases at the position of the first NOx sensor, and
• determining, using the processing unit, a scale factor for the first NOx sensor based on a combination of:
• the first amount of the reductant, wherein the first amount of the reductant is zero,
• the second amount of the reductant,
• the first set of measurement data,
• the second set of measurement data, and
• a predefined NOx conversion ratio for the first and the second amount of the reductant,
• wherein a second NOx sensor is arranged upstream of the first position and the method further comprises the steps of:
• receiving, at the processing unit, a third set of measurement data from the second NOx sensor indicative of an amount of NOx in the exhaust gases at the position of the second NOx sensor when operating the ICE at the first constant flow of NOx and dosing the first amount of the reductant,
• receiving, at the processing unit, a fourth set of measurement data from the second NOx sensor indicative of an amount of NOx in the exhaust gases at the position of the second NOx sensor and a fifth set of measurement data from the first NOx sensor indicative of an amount of NOx in the exhaust gases at the position of the first NOx sensor when operating the ICE at a second constant flow of NOx and dosing the first amount of the reductant, and
• determining, using the processing unit, a scale factor for the second NOx sensor based on a combination of:
• the first amount of the reductant,
• the third set of measurement data,
• the fourth set of measurement data,
• the fifth set of measurement data, and
• the scale factor for the first NOx sensor,
• wherein the scale factors for the first and the second NOx sensor are indicative of a measuring scale error for the first and the second NOx sensor, respectively.