My check engine light came on and my brother-in-law ran a diagnostic with the resulting code of P0740. (Honda has 135,000 Miles). I took it to a mechanic and he told me that I need to replace the transmission. I don't believe this because the car drives without any gear change issues. It runs very smoothly. Someone else told me it could be the O ring that needed replacement. And I called my Honda dealer to ask about changing the transmission fluid and filter and was told that this model did not have a filter. I asked about changing the screen and he told me that this was not done either. Honda wants to run their own diagnostic on it for $70.00. From my experience with them, they usually come up with several other things that "need" to be done. Any suggestions on how to proceed would be helpful.