Problems caused by a faulty Oxygen Sensor: When the Check Engine Light comes on due to a bad oxygen sensor, the following problems can occur: 1. Poor Fuel Economy – The engine may burn more fuel than normal. 2. Rough Idling and Misfiring – The car may shake at idle or misfire while driving. 3. Increased Emissions – The exhaust will produce more harmful gases. 4. Engine Performance Issues – You may feel loss of power, hesitation, or stalling. 5. Failed Emission Test – The vehicle can fail inspect