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Gary, ASE Certified Technician
Category: Mercedes
Satisfied Customers: 1054
Experience:  Senior Technician
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Was on freeway accelerating when the car made 1 loud knock

Customer Question

Was on freeway accelerating when the car made 1 loud knock noise went into limp mode and engine light came on. What are the possibilities.
07 s65 amg benz
Submitted: 1 year ago.
Category: Mercedes
Expert:  Gary replied 1 year ago.

Hi there,

You say 1 knock, or continuous knocking until you turned the engine off?

Could be one of few things, but any loud knock from the engine is not going to be easy or cheap to repair.

How many miles has the engine done?


Customer: replied 1 year ago.
1 knock. Could have been a backfire. Engine has 52k. Doesn't get driven much. Engine does not knock when running. But it doesn't rev up like normal and seemed to be stuck in 2 or 3rd gear.
Expert:  Gary replied 1 year ago.

Ok, that is hopefully not too bad.

You need to get the car scanned for DTCs set.

The trans is in limp home mode as well, result of the low power engine problem.

Can you get the car to a good workshop or your dealer?


Expert:  Gary replied 1 year ago.

Hi again,

Have you had a chance for a workshop to look at your car?


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