What is the common cause of P0440 code showing up on the check engine light? on 2001 Lexus RX300

I have been disconnecting the battery cable to turn off the check engine light but within one or two gas fillups it comes back on!

Asked by for the 2001 Lexus RX300
disconnecting battery will not clear code, you need a scanner. the po440 is and evap control issue. you ned to seek a diag from a good mech these can be tricky