- 1). Take the pug outside, and feed him treats near parked cars. Once the pug is comfortable around parked cars, offer him treats next to an automobile with the engine running. If the pug continues to bark at parked cars, walk the dog in circles around a parked car until it appears comfortable. Repeat this process for parked cars with running engines. If the pug does not bark, praise the dog, and offer him a treat.
- 2). Take the pug to an empty parking lot (a school parking lot on a weekend works well), and have an assistant drive slowly around the parking lot while the owner remains a safe distance away with the dog. Guide the pug with his leash at a safe distance from the car, and let the car pass slowly by the dog and owner. Repeat this process until the pug ceases to bark. If the pug does not bark, praise the dog, and offer him a treat.
- 3). Employ a bark collar if the pug continues to bark at cars. Bark collars, however, should be a last resort. Bark collars are available with noise deterrent devices, as well as citronella spray devices. Do not use shock collars.
Source...