2018 GMC Sierra 2500HD Key Fob Programming Guide

As an ASE-certified electrical technician and automotive locksmith, I frequently get calls from 2018 GMC Sierra 2500HD owners who have lost a key or just need a spare. GM trucks are rugged workhorses, but when it comes to modern security systems, they are just as complex as any luxury vehicle.

If you are looking to replace or program a key fob for your 2018 Sierra 2500HD, this guide breaks down everything you need to know, from battery replacement to programming requirements.

Quick reference

Step-by-step on-board programming

If you are hoping to program a new key fob for your 2018 GMC Sierra 2500HD in your driveway without tools, I have some bad news: GM eliminated on-board, DIY key and remote programming for this generation of the Sierra.

In older GM trucks, you could navigate through the Driver Information Center (DIC) to a "Relearn Remote Key" screen. For the 2018 Sierra 2500HD, this feature is no longer accessible to the user. The vehicle's theft-deterrent system requires a professional OBD2 diagnostic scan tool with active subscription access to GM's immobilizer programming network to pair new fobs.

The Professional Programming Process (What to expect):

1. Key Cutting: The blank high-security HU100 key blade must be laser-cut by a professional using a specialized CNC key machine to match your ignition.
2. OBD2 Connection: The locksmith or dealer connects a specialized programming tool to the OBD2 port under the driver's side dash.
3. Security Access: The tool communicates with the vehicle’s Body Control Module (BCM) and bypasses a timed security wait (usually 10 to 12 minutes).
4. Key Learning: Once security access is granted, the system is wiped of lost keys (optional but recommended) and the new transponder/remote data is paired to the vehicle.
5. Testing: The technician cycles the ignition and tests all remote functions (lock, unlock, panic, remote start).

Battery replacement

If your current fob is just suffering from poor range or an intermittent signal, it likely just needs a new battery. The 2018 Sierra fob uses a standard CR2032 battery.

1. Press the chrome button to deploy the flip-key blade.
2. Look inside the channel where the key blade usually rests. You will see a small seam for the back cover.
3. Insert a flathead screwdriver or a trim tool into the seam and gently pry the back cover off.
4. Remove the old CR2032 battery.
5. Insert the new battery with the positive (+) side facing up.
6. Snap the back cover back into place firmly until all edges are seated.

Where to buy a replacement fob

You have three main options when sourcing a replacement key fob for your Sierra 2500HD:

• The Dealership: Buying directly from a GMC dealer ensures you get an OEM key that will work flawlessly. However, it is the most expensive route. Expect to pay anywhere from $150 to $250 for the fob itself, plus another $100 to $150 for cutting and programming.
• An Automotive Locksmith: Locksmiths usually stock both OEM and high-quality aftermarket keys. A locksmith can come directly to your home or job site, cut the key, and program it on the spot. Expect to pay $150 to $250 total for an aftermarket key, cutting, and programming.
• Amazon / Online Retailers: You can buy aftermarket fobs online for as little as $20 to $50. Pros: Very cheap upfront cost. Cons: You still have to pay a locksmith to cut and program it (usually $75-$125). Keep in mind that some locksmiths will not guarantee customer-supplied online parts, as cheap circuit boards often fail during the programming process.

If on-board programming isn't supported

Since on-board programming is not an option for the 2018 Sierra 2500HD, you are dealing with a robust immobilizer system. The key utilizes a GM transponder chip embedded directly into the flip-key housing. When the key is turned in the ignition, the truck's anti-theft system energizes an antenna ring that reads this chip. If the chip isn't recognized, the fuel system is disabled, and the truck will not start.

If you have lost all your keys, expect the cost to be slightly higher, as a locksmith will need to decode your door lock cylinder to originate a new key cut from scratch, rather than simply duplicating an existing key.

Need a professional to get your truck back on the road? Find a mobile locksmith or shop on Repairius.