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Description
Holley Terminator X Engine Management Systems 550-904TERMINATOR X MPFI, 4. 8 6. 0 EARLY TRUCK Take control of your LS engine with Terminator X! Don't settle for a junkyard ECU with a cumbersome tuning interface when you can have complete control of your engine, self learning fuel strategies and the proven, race winning technology of Holley EFI at a budget friendly price! Terminator X features real time fuel learn, high impedance injector drivers, an integrated 1bar MAP sensor, and 4 programmable inputs
TERMINATOR X MPFI, 4.8-6.0 EARLY TRUCK
Take control of your LS engine with Terminator X! Don't settle for a junkyard ECU with a cumbersome tuning interface when you can have complete control of your engine, self-learning fuel strategies and the proven, race-winning technology of Holley EFI at a budget-friendly price! Terminator X features real-time fuel learn, high impedance injector drivers, an integrated 1bar MAP sensor, and 4 programmable inputs and outputs. The inputs and outputs are ideal for electric fans, boost control solenoids, progressive nitrous control, and much more. Terminator X comes fully loaded with base maps for common LS engine combinations to get you out of the garage and on the road/track fast. The 3.5" touch screen LCD handheld contains an easy to use calibration wizard as well as tuning and gauge display functions. Also included is Holley EFI's industry-leading, easy to use software suite that allows full laptop access for advanced users. Whether you are building a budget beater or a boosted race car, Terminator X has the features and technology you need at a price that won't break the bank!
Features:
- For GM LS Engines with 24x crank reluctor and Multec 2 Injectors
- Real-Time fuel map learn, takes the guess work out of tuning your base fuel table.
- High Impedance Injector Drivers will safely power most Stock LS injectors, and Holley EFI Injectors. Injector support chart provided in the instructions (Will not control Low Impedance Injectors)
- All of the new Terminator X systems utilize the Bosch LSU 4.9 wideband to relay AFR information to the ECU for accurate reading and precise tuning control.
- MAP Sensor vacuum hose adapters (1/8th – ¼ and 3/16ths)
- 4 Outputs – Ground, PWM - , for accessories such as; fans, boost control, nitrous control, IAC Kit, and More
- 4 Inputs – 12v, Ground, 5v, and Frequency, for things such as additional pressure sensors, or activation triggers for nitrous activation, or a trans brake
- Boost Control – Boost vs Time, Boost vs Gear, Boost vs RPM, Boost vs Speed, Boost Safeties
- Nitrous Control – Single Channel of Wet or Dry, Progressive or Non-Progressive, Rich/Lean Safeties, and target Closed Loop AFR
- On-Board Diagnostic LEDS for: ECU Power – Engine Run – Wideband Status – TPS Calibration – Crank Signal –Cam Signal. Allow you to identify any Critical engine issues at a glance
- Advanced Tables – 4x 1D Tables, 1x 1D per Gear Table, 4x 2D Tables, 1x 2D per Gear Table, can be used for any custom tables you can dream up, such as Flex Fuel Sensor Offset Table, or a custom fuel or oil pressure safety!adjustable through included 3.5” f
- The included 3.5" Touchscreen Handheld contains a calibration wizard, that allows you to quickly build a base tune for any LS engine. Additionally the handheld provides internal data-logging and a fully customizable gauge display.
- The compact ECU size allows you to mount it virtually anywhere. Remember, diagnostic LEDS must face up!
- Plug and play compatible with more Holley EFI accessories such as; analog style gauges, shift lights, various modules, and coming soon, 12.3" digital dash support!
- Free EFI Tuning Software for complete control of your Terminator X power plant
- Includes: 24x LS Engine Main Harness - Multec 2 Injector Harness - Terminator X ECU - ECU Main Power Harness - Bosch LSU 4.9 Wideband Oxygen Sensor - Input/Output Harness - and assorted vacuum adapters.
Application
- 2003 - 2006 Chevrolet Express
- 2003 - 2006 GMC Savana
- 1999 - 2006 Chevrolet Silverado
- 1999 - 2006 GMC Sierra 1500
- 2000 - 2006 Chevrolet Tahoe
- 2000 - 2006 GMC Yukon
- 2002 - 2007 Chevrolet Avalanche
- 2002 - 2006 GMC Yukon XL 1500
- 2003 - 2005 Chevrolet TrailBlazer EXT
- 2003 - 2004 Isuzu Ascender
- 2003 - 2004 GMC Envoy XL
- 2003 - 2004 Chevrolet SSR
- 2004 Buick Rainier
- 2002 - 2007 Chevrolet Silverado 1500
Specs
| Brand | Holley EFI |
|---|---|
| Crank Reluctor | 24x |
| Emission Code | 3 |
| Ignition Type | GM LS 24x |
| Injector Connector | Multec 2 |
| Product Type | Terminator X LS MPFI |
| Terminator LS Options | Fuel, Spark |
| Part Number | 550-904 |
Shipping Notes
- Free Standard Shipping on $100+ Orders to the USA.
- Except Preorder products are shipped in 48 hours.
- Delivery to the USA:
- Standard Shipping : 3-10 business days
- If time is of the essence, please consider selecting expedited delivery for faster service.
Exchange/Return Notes
- We offer a 30-day return/exchange service after receiving.
- Final sale items are not eligible for returns or exchanges.
- To process your return/exchange, please contact us at [email protected]
- Please click here for more details>>> Return & Exchange Policy
4.1 ★★★★★
Based on 17 reviews
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Product Reviews
★★★★★ 5
The Toy Annie Always Comes Back To
Size: X-Small, Color: Pink
⭐⭐⭐⭐⭐
These have become one of Annie's all-time favorite toys.
Annie is a tiny 4-pound dog, and she can be surprisingly picky about toys. She has a basket full of options, but she consistently comes back to her nubby Nylabones.
I think the size and texture are a big part of why she likes them so much. They're easy for her to carry around, chew on, and play with by herself. Whenever I buy a new one, it quickly becomes part of her regular toy rotation.
As a small-dog owner, I appreciate finding toys that are appropriately sized and actually get used instead of being ignored after a few days.
If you have a tiny dog who loves to chew, these are definitely worth trying. They've been a favorite in our house for a long time.
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Reviewed in the United States on May 30, 2026
★★★★★ 4
Dogs love these!
Size: Small, Color: Pink
My miniature Goldendoodle puppies love these! The only drawback is after several weeks of chewing, the bones develop pretty sharp edges long before the actual bone has been worn down. At that point, they are dangerous for the dog’s gums and must be thrown away.
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Reviewed in the United States on June 3, 2026
★★★★★ 5
🦴 Micro Bone, Major Relief; Perfect Puppy Teething Chew Toy
Size: X-Small, Color: Blue, Size: X-Small, Color: Blue
🐾 Hi, I’m PVD; teething survivor, nub enthusiast, and gum massage advocate.
This tiny blue bone was my day-one favorite from 8 weeks to 5.5 months, it handled every chew session, tantrum, and tooth eruption with dignity. I’ve officially “aged out,” but I still salute it.
⭐ Why it earned 5 stars:
✔️ Perfect XS size for toy breed jaws
✔️ Soft on sore gums, durable enough for dramatic chewing
✔️ Ridges + nubs = mouth spa treatment
✔️ Chilling it = elite teething relief
✔️ Kept me busy and prevented chewing on illegal things (furniture, shoes… mother)
🌀 Why I’m now gracefully retiring it (but still recommending):
✘ Jaw strength and confidence grew but I didn’t vibe with the larger size versions (tried and rejected them with judgment)
✘ Texture now too gentle for my post-teething chew style
✘ Advanced chewers may get bored once the rage-chewing era passes
✘ I get gum relief via Nylabone Nubz edible chews now
Best For:
• XS-Small breed puppies, especially under 5 lbs
• Teething stages + gum relief
• Delicate chewers or fur babies still in the love-bite phase
• First-time puppy parents (trust me, this bone prevents household drama!)
• 8 weeks–6 months old
🚫 Not for adult teeth or advanced chew techniques.
📝 Final Re-Barks:
Iconic starter bone for toy breed pups. Affordable, safe, and genuinely soothing during teething chaos. It carried me through the hardest months (and saved several legs; both human and furniture). I’ve outgrown it; but I’ll forever endorse it for the next generation of tiny chewers.
— PVD (Tiny Tooth Graduate, Former Chew Therapy Success Story 🧊🦴)
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Reviewed in the United States on September 17, 2025
★★★★★ 3
Nylabone Puppy Treat Starter Pack - A Mixed Bag of Delight and Disappointment
Size: Small, Color: Blue
I recently purchased the Nylabone Puppy Treat Starter Pack for my adorable 5lb puppy, and overall, I have mixed feelings about this product. While I was initially satisfied with the variety pack, one of the bones in particular left me disappointed due to its lack of durability.
Let's start with the positives. The Nylabone Puppy Treat Starter Pack comes with three different toys: a blue puppy teething toy, a nylon dog toy, and a chew treat. This variety is great for keeping my puppy engaged and entertained, especially during the teething phase. The blue puppy teething toy is specifically designed for soothing sore gums, and my puppy seemed to find great relief when chewing on it. It has a pleasant texture that is gentle on the teeth and gums, making it an ideal choice for teething puppies.
The nylon dog toy included in the pack is durable and sturdy. It has a satisfyingly textured surface that provides an excellent chewing experience for my little furry friend. The toy is designed to withstand the strong chewing habits of puppies, and it has certainly proven to be long-lasting compared to other toys I've tried in the past. My puppy enjoys gnawing on it for extended periods without any signs of damage.
Now, let's address the bone that failed to meet expectations. One of the bones included in the pack was devoured by my puppy within a single evening. I was taken aback by how quickly it was consumed, especially considering my puppy's small size. While the other bones in the pack held up well, this particular one lacked the durability I had hoped for. I understand that puppies have strong jaws, but I expected the bone to withstand more than a few hours of chewing.
Despite this disappointment, I must mention that the bone did not cause any harm to my puppy. It is important to supervise your puppy while they chew on any toys, especially if they have a tendency to swallow large chunks. In this case, I was fortunate that my puppy did not experience any adverse effects after consuming the bone. However, it's crucial to exercise caution and ensure that your puppy doesn't ingest anything that could potentially be harmful.
Overall, while the Nylabone Puppy Treat Starter Pack has its upsides, I cannot ignore the fact that one of the bones failed to meet expectations in terms of durability. However, the other toys included in the pack provided a satisfactory experience for my puppy, and they have proven to be long-lasting. I would recommend this product with the caveat that you closely monitor your puppy's chewing habits and potentially avoid the bone that didn't hold up well in my particular case.
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Reviewed in the United States on May 31, 2023
★★★★★ 5
⭐⭐⭐⭐⭐ Great for teething puppies
Size: Small, Color: Pink
I purchased the Nylabone puppy chew toys for my teething puppy, and they’ve been a big help. The toys are the perfect size for a young puppy and feel durable without being too hard.
My puppy enjoys chewing on them, and they’ve helped redirect chewing away from furniture and shoes. I also like that they’re designed specifically for puppies, so they’re gentle enough for growing teeth and gums.
The variety in the set keeps my puppy interested, and the toys have held up well with daily use. They’re easy to clean and feel safe to give to a puppy.
Overall, these are great chew toys for puppies. They’re effective, well made, and helpful during the teething stage. I would definitely recommend them to new puppy owners.
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Reviewed in the United States on December 15, 2025