An exhaust system for a vehicle and method of operating the exhaust system. The exhaust system comprises an internal combustion engine, an exhaust throttle valve, and a pressure sensor. The method comprises the steps of: outputting an exhaust gas from the internal combustion engine; determining a flow factor for the exhaust throttle valve; conducting a diagnostic pressure analysis using one or more pressure readings from the pressure sensor; estimating a stuck position for the exhaust throttle valve; determining a flow limit based on the estimated stuck position; and mitigating one or more exhaust system effects based on the flow limit and/or the estimated stuck position.