These instructions apply to the Chrysler 300 Mk1 (LX) 2004-2011.
For other models, please choose your vehicle here.
The first-generation Chrysler 300 (LX, 2004–2011) uses the Sentry Key immobiliser, so every ignition key carries a transponder the car must recognise. If you already hold two programmed keys, you can add a spare yourself in under a minute — no scan tool needed.
Before you start
- You must already have two valid, already-programmed keys — with only one key, a dealer or locksmith with a scan tool is required.
- Have the new key’s blade cut to match your locks first; cutting the blade and programming the transponder are separate jobs.
- Sit in the car with the doors closed and the new key ready before you begin.
Programming a Spare Key — Step by Step
- Insert the first valid key into the ignition and turn it to ON for 3 to 15 seconds, then turn it OFF and remove it.
- Within 15 seconds, insert the second valid key and turn it to ON. Wait about 10 seconds until a chime sounds and the security warning light flashes — this signals the system has entered key-programming mode.
- Within 60 seconds, insert the new key (blank, ready to be programmed) and turn it to ON. A single chime confirms the new key is now programmed.
- To add another key, repeat step 3 with the next blank key while still in programming mode. Up to eight keys can be programmed to the vehicle in total.
When It Won’t Work
- You only have one working key: the self-programming method cannot start, so a dealer or locksmith with a scan tool is the only route.
- The new key’s blade has not been cut, or it is the wrong type of blank — it may program the transponder but still won’t turn the lock, or won’t be recognised at all.
- The 15-second or 60-second window lapsed: the car drops out of programming mode. Turn everything off and start again from the first valid key.
- An aftermarket key of the wrong FCC ID or frequency won’t pair with the Sentry Key system — use a correct-specification blank for the LX 300.
Frequently Asked Questions
Can I program a key with only one key?
No. The Chrysler 300 LX requires two valid, already-programmed keys to self-program a spare. With a single key, you’ll need a dealer or an auto-locksmith who has a scan tool.
How many keys can the car hold?
Up to eight keys can be programmed to a first-generation 300 at any one time.
Does the blade need cutting too?
Yes. Programming the transponder only teaches the car to accept the key electronically; the metal blade must still be cut to match your door and ignition locks. A locksmith or dealer can cut it.
Is this the same as starting with a dead fob?
No. This is about adding a working spare key. Starting the car when a key fob’s battery is flat is a separate procedure covered in its own guide.
If the security or theft-warning light stays on after programming, or a related fault code is stored, you can look the code up on autodtcs.com.
Independent guide — not affiliated with Chrysler. Always follow your official service manual and safety precautions. Read our full disclaimer.