Why Does My Check Engine Light Keep Coming On. This is a question we get asked about frequently. The Check Engine Light is supposed to come on when the vehicles emission levels increase 1.5% above EPA emissions standards. The vehicles onboard computer is monitoring the sensors and the oxygen content in the exhaust. The PCM can correct for small problems such as engine wear and fuel quality to a certain extent. If a sensor sends back a reading that is higher than the emission standards the Check Engine Light comes on. When you take your vehicle to a shop to get checked out, they hook a scan tool to your vehicle. This helps to get the codes and a diagnostic starting point. One of the misconceptions that is out there is the scan tool tells you what part to replace and then your Check Engine Light will go off. While this may happen once in a great while the truth is that a lot of parts get replaced that don’t need to be and ends up costing you, the consumer a lot more money than is necessary. The best thing to do is take your vehicle to reputable shop with correct equipment and get it diagnosed correctly the first time. While the Diagnostic Fee may seem expensive it will end up saving you money. Its always better to diagnose the problem instead of throwing parts at the problem. If your Check Engine Light Is On give us a call and we will be happy to diagnose your vehicle for you.