Hi, I am new in the forum, but I have been following up the topics for a while. I own a 2001 ML 320 and my problem is also the check engine light. It has been on for a while and I thought it might be related to the recall for the catalytic converter. I called the service to set up the appointment for the recall and asked them about the check engine light but they told me catalytic converter does not turn the check engine light on and they would charge about $200 just to diagnose why the light is on. It really does not make sense to me actually, how a failed catalytic converter would not trigger the check engine light. Do you know if that is right? I do feel a little vibration in the car when I am stopping on a red light of on idle, but not sure if it is related to the converter of the check engine light. Any advice would be welcome. Thanks in advance.