The CEL (check engine light) has been on for over a year. A mechanic replaced the solenoid/sensors to no avail. He said the car should be ok even if the CEL is on. What I've noticed is the car jerks when down shifting. I know this isn't normal so I asked another mechanic who said that the timing sprocket needs to be replaced which requires pulling the engine. The cost would be in the neighborhood of $ 6000.00. I then took the car to a dealer since it was due for a C service. I mentioned to the service advisor that the CEL has been on for a while. Upon inspection they told me that indeed, the timing sprocket had to be replaced. I was quoted the same amount. I then called Mercedes to see if they would cover the repair. They did! They are paying 100% for parts. However,they are just covering 50% of the labor which is about $ 2000. I appreciate what Mercedes is doing by covering most of the repair costs, although I believe that they should cover 100% of the cost since this appears to be a manufacturer defect. This is evident because thay are covering most of the repairs even if the car's warranty has expired. I called Mercedes again to see if they would cover the entire cost. They said no and advised me to hang on to the receipt and turn it in for reimbursement if and when a recall is announced in the future. I've seen a number of posts decsribing the same problem with the same model year. TIME TO ISSUE A RECALL!! How about it Mercedes?