Question 1

Do I have to go to the Cadillac dealer to get a replacement key for my 1999 Seville?

Accepted Answer

No. A mobile locksmith with the right GM-compatible programming tools can handle this on site. The 1999 Seville uses a transponder key system that was well-established by the late 1990s across GM's lineup, and the programming process goes through the OBD port the same way a dealer's equipment does. You don't need a Cadillac-specific shop. What you need is someone who carries the right tool and knows the platform.

The dealer route also means scheduling, potentially towing if you're down to zero working keys, and sometimes a multi-day wait depending on their service queue. Cadillac stores are spread thinner than Chevy or GMC dealers, so the appointment lag can be real. For a vehicle this age, coming to you and finishing the job in one visit is a much better option.

Question 2

What exactly is a transponder key and why can't I just get a copy made at the hardware store?

Accepted Answer

The key for your 1999 Seville has two jobs. The blade turns the lock cylinder, which is purely mechanical. But inside the key head there's a small transponder chip with no battery. When you turn the ignition, the car sends a radio signal to that chip, the chip responds with a code, and the immobilizer checks whether that code is authorized. If it matches, the engine runs. If it doesn't, the car cranks and dies, or won't start at all.

A hardware store copies the blade. It ignores the chip entirely because they don't have the equipment to deal with it. The copy will turn your ignition and do nothing else. That's why programming matters, and that's what I do on site.

Question 3

How long does the dealer process actually take for a Cadillac key replacement?

Accepted Answer

Longer than most people expect, and that's before you factor in the appointment wait. The programming procedure itself isn't instant, and dealers often bundle it with a diagnostic write-up for a vehicle this age. Owners on GM forums regularly report half-day visits for key work that wasn't complicated.

On top of the time in the bay, if you have no working key, you're looking at a tow to get there. With EZ Car Keyz, I come to you in Lemon Grove, work right at your car, and the job is typically done in under an hour. No tow, no waiting room, no leaving your vehicle overnight.

Question 4

My 1999 Seville starts fine sometimes and then won't start at all other times. Could this be a transponder issue?

Accepted Answer

Yes, and it's one of the more common complaints on late-1990s GM transponder vehicles. Intermittent no-start where the engine cranks but won't fire, or fires and immediately stalls, points directly to the transponder not being read consistently. It can happen when the transponder chip inside the key head is cracked or damaged, when the antenna ring around the ignition cylinder is failing, or when the connection between the antenna ring and the vehicle's security system is getting flaky.

A lot of owners chase this as an electrical or fuel problem for a while before someone checks the security system. If your dash is showing any kind of theft or security warning during the no-start events, that's a strong indicator. Bring that information when you call because it helps narrow down whether the issue is the key itself, the antenna ring, or something deeper in the security circuit.

Question 5

Can I program a second key myself at home to have a spare?

Accepted Answer

On some GM vehicles from this era there is an onboard relearn sequence that lets you add a key without a scan tool, as long as you already have two working programmed keys. The 1999 Seville may support a variation of this. But if you're down to one key or zero keys, that onboard sequence won't work and you need someone with programming equipment to enroll the new key directly. Getting a spare made while you still have a working key is always the smarter move. Call me and I can tell you whether your specific situation qualifies for the simpler route or needs the full tool-based process.

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