How do you reset passkey II on 1999 cadillac sedan deville?

There's no "Passkey II" reset procedure in the sense of entering a code to erase the system's memory of your keys. The Passkey II system (the theft-deterrent system used in many 1999 Cadillacs) links your ignition system to your transponder key. If you lose your keys, you can't simply reset it yourself.

Here are your options:

* Dealership: This is the most reliable and recommended method. A Cadillac dealership has the specialized equipment and software to program new keys and effectively "reset" the system by programming new transponder keys to the vehicle's computer. They'll likely need proof of ownership.

* Locksmith: Some locksmiths specialize in automotive security and may be able to program new keys for your Cadillac. Make sure they explicitly state they have experience with Passkey II systems and your specific Cadillac model year. Be cautious and choose a reputable locksmith with good reviews. They'll likely be more expensive than a dealership.

Important Note: Avoid any methods claiming to reset the Passkey II system with DIY tricks. These are unreliable and often scams that may damage your car's electrical system. There's no secret button or code to reset the system. The only legitimate way to regain access is through professional key programming.