Engine light came on had it tested came up code p1436, by pass valve malfunction what is it?

Question

engine light came on and stays on, car seems to run ok however just to be safe I did not drive it on long trips. Waited for openings with mechanics but they are over booked. Went to auto zone to have the diagnostic check and she came up with code p1436 and it read by-pass valve malfunction. We don't know what that means. I took it to Meineke two months earlier with engine light on and they fixed it, replaced plugs, sensor, had a tune up and it ran fine. He said come back if light comes on again we may need to replace Cat. toyota prius 2003 I don't know what the code means.