2021 Chrysler 300 Key Replacement

2021 300 key specs

For 2019 the 300 kept the same fob shape but moved to a Hitag AES transponder and a new FCC ID, M3M-40821302, so a 2018 fob will not program to a 2019 car even though the two look alike. Buttons are lock, unlock, trunk and panic, with remote start on equipped cars, and the emergency blade slides out of the case. The final 2023 model year included a 300C with the 6.4-liter V8, and its key follows the same pattern.

What's specific to the 2021 300

The 2021 Chrysler 300 is the third of 5 model years in the 300 LD (2nd generation, AES smart key) (2019–2023), so it shares its key system with the rest of that run, which makes replacement parts easy to source. A 2021 Chrysler 300 is about 5 years old now. Original fob batteries are near the end of their life at this age, so weak range or a "key not detected" message is often a battery before it is a failed fob. Cars this age are often on their second owner, which is when a single remaining key and a request for a spare tend to show up.

Smart-key cars like the 2021 300 can be targeted with relay attacks that extend the fob's signal from inside your home, so keep fobs away from exterior walls or in a signal-blocking pouch, and have any missing fob erased from the car.

Key options for the 2021 Chrysler 300

• Smart proximity key (push-to-start). Making a new smart key is mostly a programming job. The fob has to match the vehicle's FCC ID, frequency and chip, and then the keyless system must be told to accept it, normally through the OBD-II port. Depending on the platform, that can mean entering a PIN, waiting through a timed security procedure, or on some newer vehicles, using manufacturer online access. When every key is lost, certain models need a module removed and read on the bench. For your Chrysler 300 LD (2nd generation, AES smart key), we'll tell you which of those applies, and if a step is dealer-only, you'll hear it before we drive out. The emergency blade hidden inside the fob is cut by code during the same visit.

How the Chrysler immobilizer works on the 300

• Supplier listings show the 2019–2023 300 fob with an NXP Hitag AES 128-bit chip, the same family used in the 2017-and-later Pacifica.
• The 2023 model year was the last for the Chrysler 300.
• The secure gateway module that arrived for 2018 still applies, so tool access is part of every key job on these cars.

Programming a 2021 300 key

These cars combine the AES fob with the secure gateway module, so programming needs a current tool, a gateway bypass or authenticated connection, and the vehicle PIN. Adding a spare to a car with a working fob is usually straightforward. With every fob lost, some cars can be done over OBD-II and others need the radio frequency hub handled on the bench or a dealer visit, so we confirm by VIN first.

Spare fobs are routine; all-keys-lost on these AES cars sometimes needs module work or a dealer visit.

Lost every key to your 300?

Losing every key is usually recoverable on a Chrysler without towing it to a dealer. For bladed keys, we decode a door lock or cut by code from the VIN record after confirming you own the vehicle, then program a new transponder or remote-head key through the OBD-II port. Fobik-equipped vans and sedans need no ignition cut, so that work is mostly electronic plus a new emergency insert for the door. The harder cases are the AES-encrypted smart keys on the Pacifica, Voyager, 2015–2017 200 and 2019–2023 300, where some vehicles need the radio frequency hub handled directly or a dealer visit, and the Crossfire, whose Mercedes-derived keys are normally ordered pre-coded. We tell you which case applies before we drive out.

1. Gather your documents and the VIN. Call with the year, make, model and VIN if you can read it through the windshield, plus where the car is parked. Those details let us confirm whether your Chrysler 300 can be done on-site and bring the right key, so the first trip is the only trip.
2. Get into the vehicle without damage. Entry comes before key-making because we need access to the ignition, the OBD-II port and sometimes the documents in the glove box. We take care with weather stripping, door frames and paint, and we confirm the dash VIN matches your registration before going any further.
3. Originate a new key from the car. Originating a key means building it without a sample. The door lock usually reveals most of the cuts; any it doesn't are worked out by test-cutting and trying the ignition or a second lock. The finished blade should feel like a factory key, not a forced fit.
4. Program the key to the immobilizer. Next, the new key is introduced to the car's security system. Many vehicles allow this through the OBD-II port with a PIN or security procedure. Some all-keys-lost cases require reading a module on the bench, and a few platforms only allow dealer programming, which we'll tell you up front.
5. Erase missing keys and add a spare. Once the car starts, we remove the lost keys from memory wherever the system allows, so they can't start the engine if someone finds them. Making a second key during the same visit costs much less than a repeat all-keys-lost call down the road.

Why a spare key pays for itself

• A spare stored safely at home rescues you from a locked car with the fob sitting on the seat, a key dropped somewhere along a hiking trail, or a fob that stops responding on a busy morning. Keep it indoors, never in a magnetic box under the bumper.
• Some vehicles make it hard to add a key once you're down to one. Certain immobilizer systems let an owner program an extra key on-board only when two working keys are present, so a second key preserves the easy options for later and avoids a full reset.
• Electronics fail without warning. A fob dropped on concrete, run through the washing machine or soaked at the pool can quit for good. With a second programmed key, that's an annoyance you fix on your own schedule, not a stranded car that needs attention today.

Dealer or mobile locksmith?

Dealers have one clear advantage: direct access to the manufacturer's own systems. Some newer vehicles tie key programming to online authorization that only a dealer can use, and certain all-keys-lost situations on specific platforms still require it. A good locksmith knows where those lines are. Where we can do the job, we use professional programming equipment that talks to the same immobilizer and keyless systems through the OBD-II port, and in many cases the result is identical: a properly registered key that starts the car. Where we can't, we can often still help by opening the vehicle, cutting a mechanical blade from code, or helping you gather what the dealer will ask for so that visit goes smoothly. For your Chrysler 300, ask us directly and you'll get a plain answer.

300 key battery

If a new CR2032 doesn't bring the fob back, the battery wasn't the problem. Common culprits include a battery holder whose solder joints have cracked from drops, contacts corroded by moisture, worn rubber button pads that no longer reach the circuit, or a board damaged by water. We can test whether the fob is transmitting at all and inspect the board closely. Sometimes a new shell or a resoldered holder solves it; sometimes the fob has to be replaced and programmed. Meanwhile, the car can usually still be started with the fob held at the backup spot described in the owner's manual.

How the job works

1. Identify the exact key your 300 uses. We ask a few quick questions on the phone: the year, whether the car starts with a turn key or a button, how many keys you have left, and whether the remote still works the doors. Then we check the VIN against our programming references so the van arrives with the correct blank or fob, not a close guess.
2. Verify ownership before any work. California holds licensed locksmiths responsible for knowing whose car they're making keys for. We record your name, the VIN and the plate on a work order. If you aren't the registered owner, you'll need the owner's written authorization along with your own photo ID before we begin.
3. Get the key code or decode the lock. If you still have a working key, we can read its cuts directly and check them against the factory depths for the Chrysler keyway. A worn key gets corrected back to spec during this step, so the new key turns crisply instead of reproducing years of wear in a fresh piece of metal.
4. Cut the blade on-site. Our van carries a code-cutting machine that handles both traditional edge-cut blades and the laser-cut, side-milled profiles common on newer keys. The blade is cut to the code, then test-fitted in a door lock and the ignition or emergency keyhole to confirm smooth operation before any programming begins.
5. Program the chip, remote or smart key. With the blade done, we connect to the OBD-II port and register the new key with the immobilizer. Depending on the Chrysler system, this may involve a security PIN, a timed waiting period, or on-board button sequences for the remote. On some vehicles we clone a working key's chip instead, when that's the more reliable path.
6. Test everything and clear out old keys. The last step is a short walkthrough. We show you how many keys the car now recognizes, point out the dead-fob start method for your vehicle, and hand you an itemized receipt. If a spare makes sense, it's simplest to add it during this same visit while the equipment is already connected.

What affects the price of a 300 key

• The type of key. Price follows complexity. The more the key does, the more it costs to replace: brass blade, then chip, then remote buttons, then full keyless entry and push-button start. If your 300 came with different key styles by trim, the one your car actually uses is the one that sets the quote.
• Factory or aftermarket parts. Factory keys and fobs carry the manufacturer's part number and usually the highest parts cost. Quality aftermarket keys use compatible electronics at a lower price and work well on many vehicles. We tell you which options we trust for your car, and where an aftermarket version has known range or fit issues, we steer you to OEM.
• Blade style and cutting. The blade still matters on keyless cars, because the emergency insert has to fit the door lock. Cutting by code is standard for us. Decoding a door lock when no key or code exists adds time, and so does progressing any cuts the door lock doesn't show.
• Travel, timing and extra repairs. Sometimes a key problem is really a lock problem: an ignition that won't turn even with the right key, or a door cylinder that has been jammed for years. Fixing those is separate work. We point them out, explain the options, and quote the whole job up front so the bill holds no surprises.

Call (951) 903-3193 with your VIN and the keys you still have, and we'll quote the job before any work starts.

Common Chrysler key problems

• On 2008–2016 Town & Country vans and 2008–2010 300s, a fobik that will not turn or is not recognized may be a worn fob or a failing wireless ignition node. We test with a known-good fob before anyone replaces parts.
• Sebring orders get mixed up often: the sedan and convertible use Chrysler keys and fobs, while the 2001–2005 Sebring coupe uses Mitsubishi-based keys and remotes that fit none of the other Sebrings.
• Remotes bought online for 2004 and later Chryslers still have to be paired to the car. Some cars through about 2010 can learn one at home if you hold two working keys; otherwise it takes a programming tool, and used fobs must be unlocked first.
• Remote-head keys from the 2004–2014 era often crack where the blade meets the plastic head. A new shell can save the electronics, but the transponder chip has to move with them or the car will not stay running.

Tips from a mobile locksmith

• Be careful with discount fobs from online marketplaces. A listing may match your remote's shape while using a different frequency, chip or FCC ID, and many used smart keys are locked to their original vehicle. If you already bought one, send us the listing or a photo before the visit so nobody pays for a programming attempt that can't work.
• On any vehicle with a turn-key ignition, keep the key ring light. A heavy cluster of keys, tools and charms swings with every bump and slowly wears the ignition wafers and the key itself. When the key starts to stick or needs a wiggle to turn, deal with it early, before it stops turning entirely.
• Photograph the back of your fob and any key tag that came with the car. The FCC ID, part number and key code printed there make ordering a replacement faster and more accurate. Store the photos somewhere you can reach from any device, not only on the phone that might go missing along with the keys.

Proof of ownership

Making car keys is regulated work in California. Locksmiths are licensed and overseen by the Bureau of Security and Investigative Services under the Locksmith Act, Business and Professions Code section 6980 and following, and Julian's Locksmith holds company license LCO7891. Verification protects you more than anyone: a locksmith who will make a key for whoever asks will also make one for someone who wants your car. We record your name, the vehicle and its VIN on a work order, and we politely decline jobs where ownership can't be established. You can look up our license at search.dca.ca.gov.

Need a 2021 Chrysler 300 key?

Don't wait until the last key disappears. If your Chrysler 300 is down to one key, or the one you have is falling apart, call (951) 903-3193. We're a licensed California locksmith, license LCO7891, serving Southern California and the rest of the Inland Empire with mobile car key service every day from 6:30 a.m. to 11:30 p.m.