Question 1

My key broke off inside the ignition of my 2005 CTS. Can you get it out?

Accepted Answer

Yes. Broken key extraction is a standard call for me. I use pick-style extractors to grab the broken B112 blade piece without scoring the wafers inside the ignition cylinder. Once it is out, I can cut a new key from the extracted fragment or decode the lock directly and program a fresh PK3+ transponder on site. The whole job usually takes under an hour. Worth noting: the first-gen CTS ignition cylinders (2003 to 2007) wear faster than most GM locks because the B112 blade is narrow and the sidebar wafers get sloppy with age. If your key has been hard to turn for a while, the cylinder itself may need attention too.

Question 2

What is a transponder key and why does my 2005 CTS need one?

Accepted Answer

Your CTS key is not just a cut metal blade. Inside the plastic head sits a Megamos 48 transponder chip that talks to the body control module (BCM) every time you turn the ignition. The BCM sends a challenge signal, the chip responds with a coded answer, and if the math checks out, fuel and spark are allowed. No chip, or the wrong chip, and the engine cranks for about two seconds then dies. The physical cut gets the lock to turn. The chip is what actually lets the car run. If the blade snaps but the head is intact, I can sometimes transplant the chip into a new shell and save you the cost of a full reprogram.

Question 3

My 2005 CTS cranks but dies after two seconds. Is it the key?

Accepted Answer

That is the textbook PK3+ rejection pattern. The ignition lock turns, the starter spins, the engine fires briefly, and then the BCM kills fuel delivery because it did not get the right transponder response. Check the dashboard for the SECURITY or THEFT light. If it is on solid or flashing after the stall, the immobilizer is the problem, not your fuel system. A lot of CTS owners end up at a mechanic chasing fuel pump or crank sensor diagnoses when the real issue is a failing transponder chip or a chip that was never programmed correctly. One call and I can read the key on site and confirm it.

Question 4

Can I do the 10-minute relearn myself if I buy a transponder key online?

Accepted Answer

Not exactly. The three-cycle 10-minute relearn works, but the blank key you buy online still needs its Megamos 48 chip programmed to your specific BCM before the relearn will accept it. You cannot just cut a blade and sit through 30 minutes of waiting. The chip has to carry the right crypto data first. That step requires a programmer like a VVDI2 or a Smartbox. So you can buy the blank, but you still need a locksmith to prep the chip. Then you can run the relearn yourself or I can do it on the spot.

Question 5

The SECURITY light stays on and my 2005 CTS will not start at all. Is this a known problem?

Accepted Answer

Very known. GM issued TSB 02-08-49-002 covering Passlock and PK3 system false lockouts across multiple platforms, including the CTS. The body control module can lose its learned key data due to a weak battery, a voltage drop during a jump start, or just age. CTS forums are full of owners who had a perfectly good key one day and a no-start with a solid SECURITY light the next. Sometimes the 30-minute relearn resets it. Sometimes the BCM needs to be reflashed or replaced. I test the key and read BCM codes on site so you know which situation you are in before spending anything on parts.

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