how do you reset the check engine light on the E-320

You can do this by using a scantool, disconnecting the battery terminals for 10mins or fixing the problem

The first thing to do is to DIAGNOSE the code, that is indicated by the Check Engine Light. The fact that the Check Engine Light is on means that there is a problem with your engine management computer. if you just turn it off, it could be a sensor that would leave you on the side of the road at night, which of course would be less that ideal. see http://repairpal.com/check-engine-light

merecedes c 230, 2007 engine light on. what is causing this?