My 2005 xA, with 138k miles, was not shifting into overdrive. I had multiple codes and CEL. Looks like a transmission problem. I took it to a mechanic who specialized in transmission, thinking it would be a big bill. The knock sensor was throwing a code P0325. The place where I brought my car, and called Toyota support for assistance. They stated that the knock sensor has a safety feature that, when it goes bad, it prohibits the transmission from going into overdrive to keep the engine from over-revving. They replaced the knock sensor, and all is fine now with the car going into overdrive. What I expected to be a major repair turned out to be replacing the knock sensor. Pretty expensive part but beats having the transmission worked on.