Airgag Volkswagen

Hello friends, I have a problem with a 2006 Passat with the Airbar.
It turns out that the vehicle from good to First lights the airbag fault light to the customer. I have put the diagnosis machine or give me the front of the front and companion's front impact sensor with the codes of Averia 1221 and 1222 respectively. It also tells me that TB has the left back impact sensor with the fault 1638. I try to erase and nothing. Have if you throw a hand. thank you