2003 toyota camry with check engine codes P0456 and P0442:
Both codes mean: Evaporative Emmission Control System Leak Detected (very small leak)
Check the gas cap, and visually check for any loose hoses under the hood and under the car.
If something is found, repair it, then clear the codes.
Let me know.
25 years automotive experience. ASE Certified. Currently at a Toyota dealer.