Audi Tt Oil Pressure Switches Available Here. Your oil light comes on so you pull over, turn off the engine, open the bonnet and check your oil. There’s plenty. But when you restart your engine, the oil light comes on again. What’s going on? Your oil pressure switch may be faulty and need to be replaced. Since the switch activates the warning light when oil or oil pressure falls below needed levels, it’s vitally important that it works correctly. You need to know if the oil light is a false alarm or the real thing. After all, your vehicle must have the proper amount of oil and oil pressure to lubricate all the engine parts. If it doesn’t, the engine itself could be seriously damaged.