How do I bypass antitheft lock ignition and I 1999 Sunfire Pontiac

You don't. Did you lose your keys? If so go to a GM dealer with the VIN and proof of ownership and they should be able to make you a key. It wont be free though.

You can't it needs to be at the dealership

it can be done i cut the whole anti theft system out of my 1991 cadi with passlock been driving it for 10 years..soon has i fig out what i gota do to do same to sunfire ill repost

here u go i told u i find it!! From what I've seen on the web, this is what you do. Remove the covers from around the steering column. It should be a few screws underneath it. There will be 3 small wires coming from the ignition. Black, white and yellow. There are also some larger diameter wires running along the top of the steering column. Leave those alone. On the top of the column cut the yellow wire that runs from the ignition. The small one. I was told the large one is for the airbag and it will go off if you cut it so make sure it's the small one. Then you strip the black wire so some copper is showing but don't cut it. Then you take a multimeter and connect the black end to the black wire and the red end to the yellow wire that leads back to the ignition. With your meter set to read ohms, turn the car on without trying to start it. wait a few seconds so the numbers on the meter stop moving and that is the size resistor you need. You probably can't get one that exact size but you should be able to get one within 10% of it which is close enough. Mine read 530 and I was able to get a 560 watt one. To make sure it works, you can clip it on like I've done. One side of the resistor goes to the black wire and the other side goes to the yellow wire that does NOT go to the ignition. The one that goes to the ignition just tape it up and out of the way. You should be able to start your car now. If it doesn't start, just do the 10 minute thing again.