2021 Subaru Legacy Key Replacement

2021 Legacy key specs

The final Legacy generation uses the H chip in both of its key types. Lower trims have a four-button remote-head key with a side-cut blade, while upper trims have Keyless Access with push-button start. Subaru's bulletin lists a new key part number for 2020, and 2024 cars use a newer remote-head key with a thicker CR2025 battery. Smart fobs have a hidden emergency blade, and they are not interchangeable with the fobs of 2019 and earlier.

What's specific to the 2021 Legacy

The 2021 Subaru Legacy is the second of 6 model years in the Legacy BW (seventh generation) (2020–2025), so it shares its key system with the rest of that run, which makes replacement parts easy to source. A 2021 Subaru Legacy 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 Legacy 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 Subaru Legacy

• Remote head key. Remote-head keys look similar across many vehicles, but the electronics inside are not interchangeable. Getting the right one for a Subaru Legacy means matching the FCC ID and part number printed on the back or inside the case, the operating frequency, which is commonly 315 MHz on US-market cars, the transponder type, and the button layout. A trim with remote start or a power liftgate may use a four- or five-button version where a base trim uses three. We check those details against your VIN and your existing key, if you have one, before cutting the blade. A wrong match can look perfect and still refuse to program.
• Smart proximity key (push-to-start). A smart or proximity key lets a 2021 Subaru Legacy open when you touch the door handle and start with a push of a button while the fob stays in your pocket or bag. Antennas in the doors and cabin send out a low-frequency wake-up signal; the fob answers on a higher radio frequency with an encrypted reply, and the car only allows a start once it confirms the fob is inside. When the fob battery is weak, that conversation fails, which is why most designs include a backup: hold the fob against the start button or set it in a designated pocket. The owner's manual shows where, and it's worth checking before you need it.

How the Subaru immobilizer works on the Legacy

• Subaru's bulletin lists the 2020 Legacy remote-head key as part 57497AN00A and the 2021 key as AN00B.
• The 2024 remote-head key, FCC ID CWTB1G496, takes a CR2025 battery and covers the 2024 Legacy and Outback.
• Smart fobs with FCC ID HYQ14AKB, part 88835XC00A, are listed for 2019-2024 Legacy, Outback and Ascent models.
• Subaru ended the Legacy after the 2025 model year.

Programming a 2021 Legacy key

Adding a key with one working key present is routine over OBD-II, and the remote is registered alongside the transponder. All-keys-lost is more involved on these DST-AES cars: it can usually be done with dedicated Subaru software or an emulator connected through the OBD-II port, and a few cars need a module read on the bench. We confirm coverage from your VIN, and if a dealer visit is the only route, we say so up front.

Spare keys are routine. All-keys-lost needs specialized Subaru software or emulators, and a few cars may need the dealer.

Lost every key to your Legacy?

With every key gone, the model year decides the job. A 2000-2004 Subaru, a Baja, or a base model built before its line got an immobilizer just needs a key cut by code or by decoding the door lock. On 4D62 cars from 2005 through 2011 and on remote-head cars of the G-chip years, we cut the blade, erase the missing keys and program new ones in one visit. Keyless Access cars of the G-chip years and every H-chip car are harder: some tools need a working key, so we use dedicated Subaru software or an emulator, and a few cars have to go to the dealer. Brand-new platforms, including the 2026 Outback and Subaru's electric models, are usually dealer jobs for now. We tell you plainly which route your car needs and check ID and proof of ownership before any work.

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 Subaru Legacy 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. If the car is locked, we open it with non-destructive tools such as an inflatable wedge and a long-reach rod, or by picking the door lock. Some vehicles need a careful approach to avoid triggering the alarm, which can interfere with programming later.
3. Originate a new key from the car. With no key to copy, the cuts come from the vehicle itself. We retrieve the key code through manufacturer channels where possible, or decode a door lock with a pick-decoder tool. Then we cut the blade on our code machine and confirm it turns the lock smoothly.
4. Program the key to the immobilizer. All-keys-lost programming often takes longer than adding a key, because the car has no trusted key to authorize the change. We follow the procedure your Subaru Legacy requires, then confirm the engine starts and keeps running and the remote or keyless functions respond.
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

• Two drivers sharing one key is a daily negotiation. A second key lets a partner, teenager or coworker use the vehicle without handing keys back and forth in parking lots, and it means one person losing their key ring doesn't leave the whole household stuck.
• 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.

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 Subaru Legacy, ask us directly and you'll get a plain answer.

Legacy key battery

Battery details for the 2021 Legacy: CR2025 (2024 remote-head key); CR2032 (smart fob). Swap cells one at a time and match each one exactly; if a key still fails with a fresh battery, the board, buttons or programming may be the problem, which we can test on site.

How the job works

1. Identify the exact key your Legacy uses. Every job starts with the VIN, the trim and a look at any key you still have. From those we confirm the keyway, the transponder or smart-key chip, the remote frequency, the FCC ID and the button layout. Two Subaru Legacy keys that look identical can carry different electronics, so this step keeps the wrong part from ever reaching the car.
2. Verify ownership before any work. Before cutting or programming, we compare your government photo ID with the vehicle registration or title and check that the VIN on the paperwork matches the VIN on the dash. If the registration is locked inside, we open the car first, confirm the documents, and only then make the key.
3. Get the key code or decode the lock. A key is cut from a code, not a guess. When the factory code can be retrieved through manufacturer channels after ownership is verified, we use it. When it can't, we decode a door lock with a pick-decoder tool that reads the wafer positions without damaging anything, then work out any missing cuts.
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 Subaru 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. Before we leave, every function gets checked: doors, trunk or liftgate, panic button, remote range, engine start, and the emergency blade in the driver's door. If keys are missing, we delete them from the car's memory where the system allows, so a lost key can no longer start the engine.

What affects the price of a Legacy key

• The type of key. The biggest factor is technology. A plain mechanical key is a cutting job only. A transponder key adds a chip and programming. Remote-head and flip keys add a circuit board, and a proximity fob for a push-button Subaru Legacy is the most involved of all, both in the part itself and in the programming.
• All keys lost or adding a key. On some vehicles, losing the last key changes the programming entirely, from a quick add-key procedure to a full immobilizer reset or a module read on the bench. That extra labor shows up in the price, and it's the strongest argument for keeping a spare in the house.
• Programming complexity and security access. Two cars with similar-looking keys can program very differently. Newer platforms often guard key programming behind encrypted access or paid credentials, while older systems allow straightforward OBD-II pairing. We check the exact procedure for your VIN before quoting, so the number reflects the real work involved.
• Travel, timing and extra repairs. Because we come to you, the distance from our San Bernardino base and the time of the call play a part. So does anything we find along the way, such as a worn ignition cylinder or a seized door lock. You hear about each item and get a quote before we start work.

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

Common Subaru key problems

• If a Keyless Access fob battery dies, the car can usually still be started with the backup method in the owner's manual, which uses the fob and the start button. The emergency blade hidden in the fob opens the driver's door.
• Remote-head key shells tend to crack at the blade root after years on a heavy keyring. The remote board and transponder can usually be moved into a new shell with a freshly cut blade, which often costs less than a complete new key.
• Subaru smart keys use different emergency blades. Subaru's bulletin lists a 5+4 laser-cut emergency key for the 2014-2015 Forester, the 2014 Crosstrek Hybrid and the 2015 WRX, and a thinner 4+4 key on later cars. Cut the blade to match your fob, not just the model name.
• Remote-head keys from 2012 through at least 2022 mostly run on a CR1620 cell, while Keyless Access fobs from 2014 on take a CR2032. The 2024 remote-head key moved to a thicker CR2025. Inland Empire summer heat shortens coin-cell life, and shrinking range is the usual warning.

Tips from a mobile locksmith

• Learn your car's dead-fob start method now, in the driveway, rather than in a dark parking lot later. Depending on the make, you hold the fob against the start button or place it in a marked pocket in the console. Also find the hidden keyhole on the driver's door handle and practice using the emergency blade.
• 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.
• 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.

Proof of ownership

Before we cut or program a key for any vehicle, we verify that you have the right to it. Please have two things ready: the current registration or the title, and a government-issued photo ID with a matching name. We also check that the VIN on those documents matches the VIN plate on the dashboard. If the registration is locked inside the car, that's fine; we open the vehicle first, check the paperwork in the glove box, and only then make the key. If something doesn't line up, we stop and sort it out before any key is made.

Need a 2021 Subaru Legacy key?

The quickest route to a working key for a 2021 Subaru Legacy starts with a short phone call. Dial (951) 903-3193, share the VIN and where the car is parked in Southern California, and we'll tell you whether it's an on-site job, a dealer job, or a mix of both. No pressure and no surprise charges, just a straight plan.