If your 2007-2008 GMC Yukon XL 1500 is suffering from erratic shifting, getting stuck in gear, or throwing transmission codes, the culprit is often a failing Transmission Control Module (TCM). As a technician with over two decades of experience diagnosing GM powertrain issues, I’ve seen firsthand how a faulty TCM can sideline an otherwise reliable truck. This T42 series TCM, part number 24240400, is the definitive solution, arriving pre-programmed to your vehicle’s specific VIN for a true plug-and-play repair.
The TCM is the brain of your automatic transmission, managing everything from shift points and line pressure to torque converter lockup. When it starts to fail, communication between the engine and transmission breaks down, leading to the frustrating symptoms you’re likely experiencing. Instead of paying for expensive diagnostic time and programming fees at a dealership, this module allows you to restore your vehicle’s performance right in your own driveway.
From the Diagnostic Bay: The “Limp Mode” Yukon
A customer brought in his ’08 Yukon XL, complaining it felt dangerously sluggish and the check engine light was on. The truck was stuck in what we call “limp mode”—3rd gear only. A quick scan pulled a P0700 (Transmission Control System Malfunction), a general code that points to a deeper issue. In my experience, this code on these GM trucks, combined with the limp mode symptom, almost always points to the TCM. After verifying power and ground at the module connector, we swapped in one of our VIN-programmed units. The entire job took less than 20 minutes. After a quick battery disconnect to clear the memory and a final scan to confirm no codes returned, the truck was shifting perfectly. The customer saved hundreds compared to a dealership visit and was back to hauling his family the same day.
Is Your Yukon XL Showing These Telltale Signs?
A failing TCM doesn’t always mean a complete transmission failure. Catching it early can save you from more costly repairs down the road. Here are the most common indicators that your 2007-2008 Yukon XL 1500 TCM is on its way out:
- âś” Harsh, slamming shifts or delayed gear engagement.
- âś” The vehicle is stuck in a single gear (often 2nd or 3rd) and will not upshift or downshift.
- âś” Check Engine Light or Transmission Warning Light is illuminated on the dash.
- âś” Diagnostic Trouble Codes (DTCs) are present, such as P0700, P0750, P0753, P0758, or other solenoid-related faults.
- âś” A noticeable decrease in fuel economy due to inefficient shifting.
- âś” The transmission seems to slip between gears or struggles to find the correct gear.
A Straightforward Guide to Installation
One of the biggest benefits of this module is its simple, no-hassle installation. You don’t need specialized tools or a trip to the dealer. For the 2007-2008 Yukon XL 1500, the TCM is conveniently located in the engine bay.
- Safety First: Disconnect the negative terminal from your vehicle’s battery to prevent any electrical shorts and to help reset the system’s adaptive memory.
- Locate the Module: On your Yukon XL, the TCM is typically mounted right next to the battery in the engine compartment. It’s a silver box with electrical connectors.
- Disconnect and Remove: Carefully unclip the electrical wiring harnesses from the old TCM. Then, unbolt the module from its mounting bracket.
- Install the New Module: Bolt the new, pre-programmed TCM into place. Securely reconnect the wiring harnesses, ensuring they click into place.
- Final Steps: Reconnect the negative battery terminal. Start the vehicle and let it idle for a few minutes. It’s a good practice to use a basic OBD2 scanner to clear any lingering fault codes from the computer’s memory.
Verified Vehicle Compatibility
This T42 TCM is a direct replacement for part number 24240400 and is interchangeable with many other GM service numbers. While this page focuses on the 2007-2008 Yukon XL 1500 TCM, it also fits a wide range of other GM vehicles equipped with 4-speed automatic transmissions like the 4L60E, 4L65E, and 4L70E. Please verify your specific model below:
- GMC Yukon / Yukon XL 1500: 2007-2008 (Transmission; next to battery)
- Chevrolet Tahoe / Suburban 1500: 2007-2008 (Transmission; next to battery)
- Chevrolet Silverado 1500 / GMC Sierra 1500: 2007-2013 (New Style, next to battery, w/o hybrid)
- Chevrolet Avalanche 1500: 2007-2008 (Transmission; next to battery)
- Cadillac DTS: 2006-2011 (Transmission; RH front engine compartment)
- Buick Lucerne: 2006-2011 (Transmission; LH engine compartment)
- And many more GM cars, trucks, and SUVs from 2006-2014.
What does a VIN-programmed TCM mean for me?
What does a VIN-programmed TCM mean for me?
It means the module arrives ready for installation right out of the box. We flash it with the latest GM software and calibrate it to your vehicle’s unique Vehicle Identification Number (VIN). This eliminates the need for a dealership visit for programming, saving you time and hundreds of dollars in fees.
Is this part difficult to install on my 2007 Yukon XL 1500?
Not at all. For your specific vehicle, the TCM is located next to the battery. The replacement process involves disconnecting the battery, unplugging a few connectors, unbolting the old module, and bolting in the new one. Most DIYers with basic hand tools can complete the job in under 30 minutes.
Will this fix a P0700 trouble code?
In many cases, yes. The P0700 code is a general fault code indicating the TCM has detected a problem. If the root cause is an internal failure of the TCM itself (which is very common), replacing it with this pre-programmed unit will resolve the code and the underlying issue.
Do I need to send my old TCM back?
No, there is no core charge or requirement to return your old part. You can dispose of it or keep it, making the transaction simple and hassle-free.
How do I know this is the right part for my truck?
This module, part number 24240400, is the correct fit for the 2007-2008 GMC Yukon XL 1500. To be 100% certain, you can provide us with your VIN during checkout, and we will ensure it is programmed for a perfect match before shipping.