Technical solutions are described for an emissions control system for a motor vehicle including an internal combustion engine. The emissions control system includes a reductant injector device, a selective catalytic reduction (SCR) device, and a controller. The controller determines a reductant energizing time for the reductant injector device based on one or more operating conditions of the SCR device. The controller further computes a diagnostic adaptation factor for the reductant energizing time based on an on-board diagnostic signal. The controller further inputs an amount of reductant into the SCR device by adjusting a reductant energizing time of the reductant injector device according to the diagnostic adaptation factor.