2021 GMC Sierra 2500HD Key Fob Programming

Quick reference

Step-by-step on-board programming

The 2021 GMC Sierra 2500HD does not support DIY on-board programming for key fobs. This means you cannot program a new key fob yourself using a series of key turns or door open/close sequences. The immobilizer system in your Sierra 2500HD requires specialized equipment (a scan tool) to program new key fobs. This equipment communicates with the vehicle's computer to securely link the new fob to your truck.

Because of this, you will need to visit a GMC dealer or a qualified automotive locksmith to have a new key fob programmed. They have the necessary tools and software to perform this procedure correctly and ensure your vehicle's security system functions as intended.

Battery replacement

1. Locate the small release button or tab on the side of the key fob. Press and hold it, then pull out the emergency key blade.
2. With the emergency key removed, you will see a slot. You can use a small flat-head screwdriver or a coin to gently pry open the two halves of the fob.
3. Carefully separate the two halves. You'll see the circuit board and the CR2032 coin cell battery.
4. Note the orientation of the old battery (usually positive side facing up). Gently pry out the old CR2032 battery.
5. Insert the new CR2032 battery, ensuring the positive (+) side is facing the correct direction.
6. Align the two halves of the key fob and press them firmly together until they snap securely into place.
7. Reinsert the emergency key blade.

Where to buy a replacement fob

When it comes to purchasing a replacement key fob for your 2021 GMC Sierra 2500HD, you have a few options, each with its pros and cons:

• GMC Dealership:

  • Pros: Guaranteed to be an authentic OEM part, and they will program it for you. You're ensured compatibility and proper function.
  • Cons: This is typically the most expensive option. Expect to pay between $200 and $350 for the fob and programming.

• Independent Automotive Locksmith:

  • Pros: Often more affordable than a dealership. Locksmiths also have the necessary programming equipment and can often come to your location (mobile service). They can provide both OEM and quality aftermarket fobs.
  • Cons: Ensure the locksmith is reputable and specializes in automotive keys. Prices can vary, but generally fall between $150 and $300 for the fob and programming.

• Online Retailers (e.g., Amazon, eBay, KeylessEntryRemoteFob.com):

  • Pros: This is often the cheapest way to purchase just the key fob itself.
  • Cons: You're only buying the physical fob; you still need to pay for programming services. There's also a risk of purchasing a non-compatible or counterfeit fob. Be very careful to match the FCC ID (DDJFLIP-T21) and OEM Part Numbers (13529661, 13589920) exactly to avoid issues. Aftermarket options like Strattec 5928127 or Keyless2Go K2GMC-53R are generally reliable.

If on-board programming isn't supported

As mentioned, since your 2021 GMC Sierra 2500HD requires a scan tool for programming, you'll need professional assistance. The cost for programming typically ranges from $50 to $150, in addition to the cost of the key fob itself. Many locksmiths will offer a bundled price for the fob and programming.

Your vehicle uses a sophisticated immobilizer system with a transponder chip embedded in the key fob. This chip communicates with your Sierra's computer, preventing the vehicle from starting if the correct, programmed chip isn't detected. This is why a simple "on-board" procedure isn't sufficient; the new fob must be electronically linked to your vehicle's immobilizer system using specialized equipment.

If you're getting a completely new key, the physical key blade will also need to be cut to match your vehicle's locks. This can usually be done by a locksmith or a dealership, often included in the service if you purchase the key from them, or for a small fee if you bring your own uncut key.

Find a mobile locksmith or shop on Repairius.