I have an 07 camry with 139,000 miles, I just had the transmisson replaced with a used trans with 70k miles, so far its running good but the check engine light came on after day 2. what could it be?

Do you plan on selling the car right now, this is the perfect time. I hope you realize that transmission problems on non-hybrid models of Toyota Camry cars are abundant. You're really rolling the dice with the "used" transmission you put in your car. Hope you didn't pay a lot for that? And, by the time you pass 150,000 miles, many other things will start to go wrong with your car. You've got an average of 17,000 miles per year on this car. That's a lot of miles for a 2007! Unless, everything else is spotless and you've had this car from day one, I would be very careful going forward.

Thank you for your honesty. I am considering getting rid of it. I'm taking it back to the repair shop to check the light, (it could be a sensor issue because it actually drives better now) once they clear it and it comes back! I will definitely sell or trade it in.