I started having a rough idle in my Canyon around 40,000 miles. I drive about 100 miles everyday highway so I blew past the 36,000 warranty pretty quick. GM put out a letter sating that anyone having a rough idle with the CEL on could come get it fixed for free. Of course, I threw the letter away before I had the problem. The shop pulled a p0300 and p0302 code off the computer which means multiple misfire (p0300) and cylinder #2 (0302). Their recommendation was a new head...at about $2,000+. I called the dealer and they have had 7 people with the same problem. Bear in mind that this is in a relatively unpopulated rural area. However, they were still covered under the 3 year/ 36,000 mile warranty. GM recommends that the shop replace the entire head. I am out of warranty already. None of the mechanics knew the exact problem because instead of locating the root, they replaced the whole head on each truck. Luckily, I had it worked on at about 30,000 miles at the dealer for an unrelated problem which should have prompted them to look up my VIN and check the head out. They didn't. But since they messed up, I am still under warranty if the problem is determined to be a "valve leak." Hopefully all goes well for of my tax return will get blown in a hurry. GM needs to issue a recall of these trucks and replace the heads! I should also point out that anyone with engine codes p014 or p017 is covered under warranty because this is due to a faulty camshaft sensor or solenoid. Hope I helped someone out.