NOx sensor diagnostics in heavy-duty motor vehicle engines

A method, comprising:

• operating a diesel engine of a heavy-duty truck such that the diesel engine generates an exhaust gas flow and the exhaust gas flow flows into an exhaust after-treatment system including an upstream selective catalytic reduction system and a downstream selective catalytic reduction system downstream of the upstream selective catalytic reduction system with respect to the exhaust gas flow;
• controlling a DEF injector downstream of the upstream selective catalytic reduction system and upstream of the downstream selective catalytic reduction system to increase a rate at which the DEF injector injects DEF into the exhaust gas flow;
• measuring a first level of NOx gases with a first NOx sensor downstream of the upstream selective catalytic reduction system and upstream of the downstream selective catalytic reduction system and a second level of NOx gases with a second NOx sensor downstream of the downstream selective catalytic reduction system as the rate at which the DEF injector injects DEF increases;
• using the measurements of the first and second levels of NOx gases to determine a level of error in measurements provided by the first NOx sensor;
• adjusting a subsequent measurement provided by the first NOx sensor based on the determined level of error in measurements provided by the first NOx sensor;
• and
• controlling the first DEF injector to inject DEF at a first adjusted rate based on the adjusted measurement provided by the first NOx sensor.

A heavy-duty truck, comprising:

• a diesel engine;
• an exhaust after-treatment system having an upstream end and a downstream end opposite the upstream end, the upstream end coupled to the diesel engine, the exhaust after-treatment system including:
• a first NOx sensor;
• an upstream selective catalytic reduction system downstream of the first NOx sensor;
• a second NOx sensor downstream of the upstream selective catalytic reduction system;
• a downstream selective catalytic reduction system downstream of the second NOx sensor;
• and
• a third NOx sensor downstream of the downstream selective catalytic reduction system, and
• an engine control unit configured to:
• operate the diesel engine such that the diesel engine generates an exhaust gas flow;
• control the diesel engine such that the exhaust gas flow has a constant level of NOx gases as it enters the exhaust after-treatment system;
• control a DEF injector upstream of the upstream selective catalytic reduction system to increase a rate at which the DEF injector injects DEF into the exhaust gas flow;
• measure a first level of NOx gases with the first NOx sensor and a second level of NOx gases with the second NOx sensor as the rate at which the DEF injector injects DEF increases;
• and
• use the measurements of the first and second levels of NOx gases to determine a level of error in measurements provided by the first NOx sensor.