That's what they told me too. Said it may change all my settings -locks and such. Well, that seems fixable. I think it's worth the chance if it increase milage by a couple of numbers. But again, don't even know if this fixes milage or not. I'd think however, if there is an update available you should be able to go in and get it no questions asked.
Here is what I found out in March when my check engine, and VSA light illuminated, and the ECO light would not:
Sorry it took me a day to get back but problem solved in about an hour.
The tech hooked up the car and although the lights did clear themselves he was able to get an error code.
The error code is a known problem, it is a software fix. There apparently is a problem that the software gives an erroneous code and lights up the check engine and VSA idiot lights. The fix is to update the software. He did and everything is now okie- dokie.
Official statement from my receipt: Updated current PCM Software with newest available version to resolve P2118 misinterpretation problem. Cleared DTC and no problems at this time.
Just for the record, my CT has no problem with mileage before or after ... as stated above the lights cleared before I got to the dealer. The tech could still pull up the error code. It was explained as a known problem, did not require a recall, but they only seem to correct it when the lights illuminate.
This was explained as only a software glitch, a false reading. My build date is July 2010.
My CT did not have any performance or gas mileage issues before or after the update. Nothing such as locks, etc., were affected, very transparent.
Don't think this has anything to do with anything expect erroneous software.