My wife's 2005 CTS w/2.8 liter V6 started throwing check engine lights that would flash for a few seconds, then go off or stay on for a couple of days and go off. OBD codes read "intermittent misfire on cylinders 2, 4, 6". I took the thing to my local Caddy dealer who has diagnosed the thing as needing three new timig chains, along with guides, tensioners, etc, to the tune of $1,350 p & l. They say this was caused by low oil levels although the oil has been changed faithfully with Mobil 1 only and the oil level light never came on. The thing has 73,000 miles on it, which makes it the only GM product I have owned since 1974 that has needed major service before 150,000 miles. Intermittent flashing lights don't spell mechanical problems to me, they say electronics. Anybody ever heard of a problem like this?