An off-duty NYPD cop fired her gun at a trio of crooks out to steal a catalytic converter from a vehicle parked in Washington Heights early Tuesday, police sources said.

The 31-year-old officer was about to drive to work when a neighbor alerted her someone was trying to steal a catalytic converter from a car near Broadway and W. 148th St. about 5:45 a.m., the source said.

She drove over to the location and was recording the thieves on her cell phone from her vehicle when two of them turned to her and reached into their waistbands as if they had guns, cops said.

The officer fired off one round from her car as the three crooks scrambled to an awaiting dark-colored BMW and sped off.

No one was hit and no arrests have been made, officials said.

Cops were called to the scene and are investigating the incident.