I have a 2001 Civic EX coupe and have a P1457 error code. this happened a few weeks ago and I replaced the evap two way bypass valve. Now the error has returned. what else could it be?

 

Before you replaced the EVAP two-way valve, did it not hold vacuum? If held vacuum - then it was good. This part is the most common part to fail when P1457. Did you replace the canister at the same time?

Time to troubleshoot the rest of the EVAP system for leaks, electrical continuity and failed parts.

 

No I didn't replace anything else. I just easter-egged it and hoped for the best. I did look at the wiring and hoses but couldn't see any damage.