[NoMoGMPG]

First out, I haven't been made aware of any widespread issues with the I-5 used in the Colorado/H3. That doesn't mean there isn't the possibility of isolated issues. I do know that we have not replaced a single cylinder head...yet. When GM requests that an assembly replaced under warranty be returned to the WPC (Warrany Parts Center) it is to determine the root cause of failure and to determine if replacement was warranted. This take time. If there is an issue, and it is widespread, then it becomes a recall or campaign to repair a defect. If it is an isolated event, usually regionalized, it goes out as a TSB (Technical Service Bulletin) and IF the issue is brought as a complaint by the consumer AND the vehicle falls under the parameters of the TSB, the repair is performed.

That is how it works.

Now, as far as replacement of the cylinder head being warranted, I believe that it is standard practice to tear it down and send it out for magnafluxing and surface flatness by a qulaified machine shop. If the valves were burned due to a lean condition, GM would pay to have the damaged valves replaced, no question. If the head is warped beyond specification, it would be replaced, no question. But if you read your new vehicle warranty, it clearly states redundantly, that GM will repair OR replace at their discretion. In other words, what would most benefit them, make the consumer happy, and cost them the least.

My guess is they suspect a calibration problem, are working on a temporary field fix to get by on, and will come out with a TSB shortly containing a recalibration.