My 2009 Chevrolet Impala has an extremely irritating knocking sound. It sounds like Woody Woodpecker is under my dashboard! Upon researching online to try to find out what the problem could be, I came upon HUNDREDS and HUNDREDS of people complaining about the very same thing. The problem is one (or more) of four ACTUATORS that is bad. Since this is apparently a very common issue, I don't understand why GM has not issued a recall on this. Seems to me since this is apparently a very large issue with GM Cars (found out it's not just the Impalas, but also common to many other GM models), that GM should do something about this and issue a recall, so that consumers can get this issue fixed. With the number of online complaints I am finding about this issue, GM could go a long way toward making their customers happy by issuing a recall to fix this widespread problem. From what I'm seeing in all these complaints, it's not a matter of "IF" this will happen to your car, it's a matter of "WHEN" - because it's happening to practically everyone who owns a GM car. With that volume, sure seems like there should be a recall on this!!