Timing chain failures under 30,000 miles are prevalent on many GM 3.6L motors and they have sent out a letter explaining that "under certain driving conditions and with extended oil change intervals, the timing chain can wear prematurely causing the service engine light to come on"... there are hundreds if not thousands of these failures documented on the auto blogs/forums.. and this is a blatant attempt by GM to change the engine performance and cause more frequent oil changes in and effort to get engines to last outside of warranty (all most all are failing within warranty. I received a letter on March 14th, 2011 from mr. [xxx], general director of customer service, asking me to bring the car in to have the ECM modified to prevent failure of a known design problem... this is totally unacceptable solution to a design flaw... causing me to take the risk of future failure and thel limit future liability by downgrading my 2007 Cadillac Sts's performance and making me change the oil sooner that their engineered oil change computerized program recommends... to prevent a failure that is almost guaranteed to happen! information redacted pursuant to the Freedom Of Information Act (FOIA), 5 U.S.C. 552(B)(6).

- San Ramon, CA, USA