Your exhaust system is more than a muffler. It is a series of pipes that run under your car, connected to your muffler and catalytic converter. The main function of your exhaust system is to control noise and to funnel exhaust fumes away from passengers. There are also sensors connected to the exhaust system that  communicate information to the computer. This can bring on the “check engine” light when the engine is not performing efficiently, exhaust leak or sensor malfunction.