Hello I've got a Mazda 3 with a 1.6 litre petrol engine. I foolishly failed to check the oil level and the engine warning light came on. Oil has subsequently been added and I've done a few thousand miles in it since with no noticeable difference to the car. However I can't turn the engine warning light off. When I plug a diagnostic tool in it reports a P0328 Knock Sensor problem. Should I change the sensor? Find whats causing the sensor to get upset? Or just ignore it since its not causing any problems? I have very limited understanding of cars (see line 3 above).