Vapor Cannister PCM Trouble Code Way back in early January 2005, our then new 2004 Chevrolet Suburban registered a "Check Engine" light. The Vehicle went to 3 different dealers for that same issue, at least a dozen times, but the trouble code was never permanently resolved at any of the Chevrolet dealers. The trouble code would always return within a month or two. During early 2007, a local Cadillac dealer's "trouble resolution" technician, researched the problem, purged the code, then using a GM factory scanner, he "expanded the parameters" for that vapor cannister system, effectively resolving the trouble code issue. He told me that this issue came up every so often, with the full size GM SUVs. My Suburban has never displayed the "Check Engine" light since that time, which has been some 6 years. Recently, during December of 2012, the speedometer went haywire in my Suburban, so the selling Chevrolet dealer ordered a new instument cluster for the SUV. This was installed during January 2013, and everything was just fine, until Tuesday PM, Feb 5, 2013. Apparently, the GM Dealer Technician flashed the PCM to verify the speedometer error, and that action has apparently set the PCM back to it's default mode. Now, We have this same trouble code AGAIN, for the vapor cannister issue. A local parts store manager authenticated the trouble code, as his scanner verified the problem as Vapor Cannister Issues. This AM, I called the dealer who recently performed the instrument cluster installation, and the assistant manager told me that he's never heard of "expanding the parameters" to solve PCM issues, and yet, he claims 36 years in the automotive business. I appreciate the fact that the Chevrolet/GM dealer did a very fine job installing the instrument cluster, however, I can no longer find the GM Cadillac Technician who corrected this vapor cannister trouble code issue, some 6 years ago. He may have retired, or moved on to another employer. My question is, what can be done to permanently resolve this Vapor Cannister Trouble Code?? The problem was non-existent for six years, and the Chevy Dealers locally seem to be lacking the ability to handle this particular issue. Is it possible for You to direct Me to someone who has this technical knowledge? My Suburban has fairly low driven miles on the odometer, is in very decent condition, and I'm currently not in the market to buy a new SUV. Perhaps in another 4 or 5 years, but it's just not in the financial plan at the moment. Thank You for any assistance rendered!