I have a 2012 Silverado, 5.3L V8, that the check engine light is on (solid).

There was a GM service bulletin on this issue, but not for the year of your truck. It's possible the problem has carried over to the following production years. Check this link for a write up and a link to the bulletin: http://engine-codes.com/p0521_chevrolet.html

I bought a used 2012 Chevy 1500 two months ago with the same problem and code. The sensor has difficulty reading the gauge but is not a major issue. Replaced sensor and problem goes away. It's a computer issue that isn't major

I am having that problem right now with my 2012 Chevy 1500. But my engine light came on the second day. I am going to have it checked out.

I had to replace this engine with 83,500 miles on odometer. Cost over $7700.00. I have put 22,000 on new engine and now check engine warning light came on today. It is a 2012 , Silverado, am not a very happy customer. Did some research and appears this engine has a history of problems. Class action law suit out East was tossed by courts.