Patent ID: 7945377

Claim:
An engine system, comprising: an engine intake; an engine exhaust; an emission control device; a low pressure EGR loop coupling the engine exhaust to the engine intake; an EGR valve positioned in the EGR loop and configured to adjust an amount of exhaust gas diverted through the EGR loop; a back-pressure valve positioned downstream of the EGR loop; one or more exhaust gas sensors positioned downstream of the back-pressure valve; and a control system with computer-readable instructions for, adjusting the EGR valve and the back-pressure valve to divert an amount of exhaust gas through the EGR loop; and in response to a request for exhaust gas sensing, modulating the back-pressure valve at a frequency higher than the adjustment to promote exhaust gas mixing while maintaining the amount of exhaust gas diversion, and sense the mixed exhaust gas downstream of the back-pressure valve.