Method for desulfurization of selective catalytic reduction devices

An emissions control system for treating exhaust gas in a motor vehicle including an internal combustion engine, the emissions control system comprising:

• a selective catalytic reduction (SCR) device;
• a controller operably connected to the SCR device and configured to perform a desulfurization method to desulfurize the SCR device by:
• injecting a reductant into the exhaust gas upstream from or into the SCR device;
• and
• increasing a temperature of the exhaust gas;
• a downstream NOx sensor operably connected to and in fluid communication with the exhaust gas, the downstream NOx sensor disposed downstream of the SCR device and operably connected to the controller;
• and
• an upstream NOx sensor operably connected to and in fluid communication with the exhaust gas, the upstream NOx sensor disposed upstream of the SCR device and operably connected to the controller,
• wherein the downstream NOx sensor is configured to measure a downstream NOx value of the exhaust gas from the downstream NOx sensor, and
• wherein the upstream NOx sensor is configured to measure a upstream NOx value of the exhaust gas from the upstream NOx sensor, and
• wherein the desulfurization method further comprises:
• measuring a downstream NOx value from the downstream NOx sensor;
• measuring an upstream NOx value from the upstream NOx sensor;
• and
• determining a NOx conversion efficiency using the downstream NOx value and the upstream NOx value,
• wherein, if the NOx conversion efficiency is equal to or less than a NOx conversion efficiency lower limit, the injecting of the reductant and the increasing of the temperature of the exhaust is initiated.