I disconnected the car battery for several minutes, and then in ForScan Lite I still saw B1239, but then I tapped on the circular arrow next to the code, then it refreshed and the code did not come back. I'm guessing that disconnecting the battery did nothing, and ForScan Lite was able to tell the PCM to clear the code.

I decided to try changing the air filter back there first (I put it in w/ the arrows facing down!) So now I'm waiting to see if the car will throw B1239 again ... hopefully it was just a dirty air filter.

 

After a day (went on a 100 mi trip), still no yellow wrench, and my MPG went up from a steady 29.6 to 33.2!

I haven't seen this kind of a fluctuation w/ MPG in the two months of various driving.

 

Yellow wrench turned on after a couple of days -- ForScan pulled B1239. So I replaced the blend door actuator (Motorcraft YH-1770, $37 from a local Ford dealer) and reset the code this wknd.

My MPG was around 34-35 right after replacing the filter but now it's settled at 31. Oh well. It was too good to be true!

 

My 2008 is working as it should, and I get 31 mpg avg when I don't run the air and I'm being reasonably conservative with my driving. Run the air and dog it a bit and it drops below 28.