how do i find this problem ?

Question

i have a trouble code p0440 on my chevy silverado 1500 i changed every egr valve new gas cap and clear the code i drove for forty miles and the code came back,what else could it be ?

Answer 1

P0440 Evaporative emission leak test malfunction

This code is for the Evap system , the main cause to set this code is the FTP (fuel tank pressure) sensor, If you have smoke tested the system and with the smoke test the evap system is sealed, Your next step is to monitor the FTP sensor

 On the fuel tank module is the FTP sensor, if this sensor is not reporting the correct fuel tank pressure / vacuum you would set a P0440