The evap system is a self contained vacuum. Instead of replacing parts you should get a brake bleeder and test for a leak a section at a time. For example, there's a line that goes into you canister. Trace back to a point where you can disconnect the hose. Connect your brake bleeder and pump to see if you can hold a vacuum. Then just keep working your way back one section at a time until you reach the gas tank. You might need a buddy to plug the opposite end of the section of line you are testing if you can't reach it with your finger. If every section of line holds a vacuum then fill your gas tank and try to draw a vacuum on the tank. If you do this methodically you will find your leak.

 

I'm kind of at the end of my rope here. Been chasing these codes for months now. I started with the obvious and replaced the gas cap with a new one from the dealer and it still came back. I replaced the purge solenoid and leak detection pump and still came back. I took it in to get smoke tested and no leaks were detected. I've visually inspected all hoses and can find no apparent or obvious cracks. I don't want to keep throwing parts at it. I am even contemplating bringing it into the dealer and just letting them take care of it but I know I will be bent over pretty badly there. I'm going to replace the charcoal canister and LDP Filter next and try again. Any suggestions if those don't work either? I'm getting frustrated I can't pass inspection.

@brunkhorse - Sorry for bringing back a dead thread but did you ever resolve the persistent P0456/0457 error codes?

 

Yes I took it into the dealer and they diagnosed it as a short in the main wiring harness. They hit me with a $500 bill to find the short and put a $2 piece of heat shrink but the light has been off.

 

OUCH! Any chance you happen to remember where the short was?

 

No. I was just so fed up at that point i didn't even care to ask. Just said fix it and then assumed the position haha

 

My vacuum leak was in the hose where it goes into the canister. Replaced a 90 degree elbow (rubber) and the next length of hose. they were cracking. just check for vacuum leaks. Hope that you find the problem.