With any code, there is a sensor that is reporting a number to the computer that is out of the normal range. In the case of P1456, it is a pressure sensor.

Now the problem could be the sensor is reading properly and you have a leak in the tank side of the EVAP system, or your sensor is not working properly. This is where you have to do some diagnostic work to find the problem.

Has any work been done your car recently?

 

Did a tuneup, changed all brake pads . Had tensioner pulley replaced 3 mos ago. That's all the most recent work done

 

Even without having any work done under the car, those rubber vacuum hoses are still about 17 years old. Make sure they aren't getting brittle & cracking.

 

Attached is some more info. to add to what was previously posted in this thread.

 

Yes i will be checking for Cracked hoses this weekend, once this part comes in.