I started getting this code on 4th gear about a month ago. After reading of the possible causes I decided to start with the easiest (and least expensive) fix, change vacuum lines from braided to silicone. That actually fixed my issue.

There seems to be a lot of confusion out there of the possible causes but one should apply judgment and start with the easiest solution first, it makes sense, right? Well, there seems to be people over complicating things and going for harder/more expensive fixes first (and not solving their issue). I am creating this post just to share with people in this forum in case someone gets this error in the future.

Before deciding to replace the vacuum lines I removed a couple of them after 20 minutes of vehicle operation and I always heard a long pressure release, even after having the car parked for two hours (some people decide the lines are not the problem because "they hold the pressure"), but I still did them because my car has 102K miles (another "make sense" fact). The ones behind the oil filter were a little brittle, the rest felt okay. During the replacement of the vacuum lines with 4mm ID silicone lines I also removed my OEM charge pipe and confirm that it was in good shape. So, right now, the car works well and no more codes on 4th or 5th (yes, I pushed it way above 100 MPH :-) ). Easy and inexpensive fix, so I'm happy!

I bought black lines from Amazon, which were a little thicker OD than OEM lines but they still fitted fine.