An internal valve leak will generate DTC P1441 if the fuel level sensor is also unreliable.
NOTE:
Purge adaptation can lead to problems when conducting fault diagnosis of the fuel system as closed loop can fluctuate around 0% despite major faults such as air leaks. By connecting an LED instead of the purge valve and reading the purge adaptation with the diagnostic tool while purging is active, the reading will indicate the entire fuel fault on condition that the multiplicative and additive adaptations have been zeroed first.