The car was running without error codes. Replaced the fuel pump as records showed it hadn't been replaced. Then PO451 started appearing. Had the shop replace the evap hose and fuel tank pressure sensor (FTP), cannister vent valve and passed a smoke test. Cannister purge valve which releases captured fuel to the intake was checked and working properly. The mechanic indicates that the fuel tank pressure sensor reads 4.7" Hg (with the gas cap off I believe) which apparently is too high. Research indicates the PCM may have to be reprogrammed to reset the offset calibration of the FTP? Any ideas would be appreciated. Thanks.

 

The FTP is a dealer part and the mechanic returned the first one and got the same problem with the second FTP. So its not the FTP.

 

The Dealer indicates that the wiring harness should have been replaced when the fuel pressure sensor was replaced. Now I have to pay to have the fuel tank removed again but hopefully, this will fix the problem.