Patent ID: 8920757

Claim:
A method, comprising: determining a dosing command that includes a quantity of a reductant to inject with a dosing system for treatment of an exhaust gas in an exhaust system that includes a selective catalytic reduction catalyst; and injecting the reductant into the exhaust system through a metering valve of the dosing system over a variable frequency dosing cycle while measuring a quantity of injected reductant, wherein the variable frequency dosing cycle includes: closing the metering valve from an open condition when either a differential pressure across the metering valve is less than a first differential pressure threshold or the measured quantity of injected reductant is greater than the quantity of reductant to inject from the dosing command; and opening the metering valve from a closed condition when the quantity of reductant to inject from the dosing command is more than a threshold amount and, when the metering valve is in the closed condition in response to the differential pressure being less than the first differential pressure threshold, the differential pressure being more than a second differential pressure threshold, wherein the second differential pressure threshold is greater than the first differential pressure threshold.