A judge in Edinburg on Tuesday then sentenced 30-year-old Gilberto Montezano to 18 months of probation and fined him $500.
Edinburg police suspended Montezano without pay last May, a month after the incident.
The McAllen Monitor reports Montezano was accused of shaking down the driver by taking the motorist's beer and an ice chest. Further details on the original traffic stop were not immediately available.
Montezano was fired during the investigation led by Texas Rangers.