Program a Spare Key Fob (Sentry Key)

The Magnum’s Sentry Key immobiliser means a newly cut spare will crank the wagon but the engine won’t stay running until the key’s chip is taught to the car. If you have two valid programmed keys and a US-market model, the Customer Learn procedure lets you add spares in the driveway without a locksmith, and it enrols the remote-entry buttons in the same pass. Keep both good keys and the blank together before you begin.

How you know a key needs programming

An untaught key starts the Magnum for a second or two and then stalls as the immobiliser cuts fuel, usually with the security lamp flashing in the cluster. A blank that has never been cut won’t turn the lock at all. Owners often meet this after buying a used wagon that came with only one key, or after ordering a cheap online transponder blank — it opens the doors but will not sustain a start, which is the classic sign the chip has never been enrolled.

1. Have each blank key cut to match the ignition lock so it turns freely.
2. Insert the first valid Sentry Key and turn the ignition to On.
3. After the ignition has been On for more than 3 seconds but less than 15, turn it Off; within 15 seconds swap in the second valid key and turn to On.
4. About 10 seconds later the security indicator flashes — you are now in Customer Learn mode.
5. Within 60 seconds turn Off, insert the blank key, and turn to On.
6. After roughly 10 seconds the indicator stops flashing, glows solid for about 3 seconds, then goes out — the key is programmed. Cycle the ignition and start the wagon to confirm.

Why you need two working keys

The two-key requirement is the immobiliser’s security lock: the car only opens its Learn window when it already recognises two trusted transponders, which prevents anyone with a single copied blank from adding more. Each chip answers a rolling challenge from the immobiliser module on every start, so an unprogrammed key never completes the handshake and the powertrain controller shuts the fuel off.

When it’s a dealer job

Respect the timing: missing the 3-to-15-second gap or the 60-second Learn window makes the system exit with nothing stored, so confirm the new key both starts and keeps the wagon running before you assume it worked — don’t retry endlessly. A key already coded to another vehicle, or any key on a non-US country-code car, will be refused. With only one working key, or none, an owner has no way in: a dealer or locksmith with the car’s PIN and a scan tool is required. The Magnum holds up to eight keys, so repeat the full sequence for each spare, then stand back and test the fob’s lock and unlock buttons to confirm the remote programmed alongside the immobiliser chip.