Is your 2007, 2008, or 2009 GMC Yukon suffering from frustrating transmission problems like harsh shifting, getting stuck in gear, or a persistent check engine light? You’re not alone. The Transmission Control Module (TCM) is the brain of your automatic transmission, and when it fails, it can make your reliable SUV feel unpredictable and unsafe. This replacement T42 TCM, part number YNXS, is the definitive solution, arriving expertly programmed to your vehicle’s VIN for a true plug-and-play fix.
From the Diagnostic Bay: The Yukon That Wouldn’t Shift
A customer brought in their ’08 Yukon, stuck in what we call ‘limp mode’—it wouldn’t shift past 3rd gear. They were worried they needed a full transmission rebuild, a multi-thousand-dollar job. After plugging in my scan tool, I saw the classic P0700 code, a general transmission fault. Digging deeper, I found communication errors with the TCM. Instead of a costly mechanical repair, the fix was simple: a new, VIN-programmed TCM. In under an hour, we had the new module in, codes cleared, and the Yukon was shifting like it just rolled off the factory floor. This part saved the customer a massive headache and a huge repair bill.
Is Your Yukon Exhibiting These Telltale Signs?
A failing TCM doesn’t always mean a complete transmission breakdown. Often, the signs are subtle at first. Here’s what to look for:
- âś” Erratic or delayed gear shifts that feel harsh or unpredictable.
- âś” The vehicle feels sluggish or refuses to shift into higher gears.
- âś” Your dashboard is lit up with a Check Engine Light or Transmission Warning Light.
- âś” Diagnostic Trouble Codes (DTCs) are present, especially P0700, P0750-P0758 (solenoid codes), or communication codes.
- âś” A noticeable drop in fuel economy as the transmission isn’t operating efficiently.
- âś” The transmission gets stuck in a single gear (limp mode) to prevent further damage.
A Straightforward Guide to Installation
One of the best features of this module is its simple, direct installation. Because we program it to your VIN before shipping, you don’t need a trip to the dealership. For a 2007-2009 Yukon TCM, the process is very accessible for a DIYer.
- Safety First: Disconnect the negative terminal from your vehicle’s battery to prevent any electrical shorts and to help reset the system.
- Locate the Module: On most GMT900 trucks like the Yukon, Tahoe, and Sierra, the TCM is conveniently located in the engine bay, right next to the battery.
- Disconnect and Remove: Carefully unplug the electrical connectors. Press the release tabs firmly. Then, unbolt the module from its mounting bracket.
- Install the New Module: Bolt the new VIN-programmed TCM into place and securely reconnect the electrical harnesses. You should hear a click as they lock in.
- Final Steps: Reconnect the battery terminal. While the system may reset, it’s best practice to use a basic OBD2 scan tool to clear any stored fault codes. Start the vehicle and take it for a test drive to confirm smooth shifting.
Verified Vehicle Compatibility
This T42 TCM (part YNXS and others) is a direct-fit replacement for a wide range of General Motors vehicles equipped with 4-speed automatic transmissions like the 4L60E, 4L65E, and 4L70E. While this page focuses on the 2007-2009 Yukon TCM, it also fits the following models. Please verify your specific model and location notes.
- GMC Yukon / Yukon XL 1500 (2007-2009): Located next to the battery.
- Chevrolet Tahoe / Suburban 1500 (2007-2009): Located next to the battery.
- Chevrolet Silverado / GMC Sierra 1500 (2007-2013): Located next to the battery (for new body style ’07+).
- Chevrolet Avalanche 1500 (2007-2008): Located next to the battery.
- Cadillac DTS (2006-2011): Located in the RH front engine compartment.
- Buick Lucerne (2006-2011): Located in the LH engine compartment.
- Chevrolet Impala (2006-2011): Located in the lower air cleaner housing.
- Hummer H3 (2008-2010): Located in the RH rear engine compartment.
- …and many other GM cars, trucks, and vans from 2006-2014. See full list for details.
Frequently Asked Questions
What is the main benefit of a VIN-programmed TCM?
A VIN-programmed TCM is ready for installation right out of the box. It eliminates the need for expensive and time-consuming programming at a dealership, saving you hundreds of dollars and getting your vehicle back on the road faster.
Will this fix a P0700 trouble code on my GMC Yukon?
Yes. The P0700 code is a general fault indicator requested by the TCM. If the TCM itself is the source of the problem (which is very common), replacing it with this module will resolve the root cause and allow the code to be cleared.
Is this part difficult to install myself?
Not at all. For most trucks like the 2007-2009 Yukon, the TCM is located next to the battery and requires only basic hand tools to replace. The entire job can typically be completed in under 30 minutes.
What happens if I don’t replace a failing TCM?
Ignoring a failing TCM can lead to more severe issues. Continued harsh shifting can cause premature wear on mechanical parts like clutches and bands, potentially leading to a complete transmission failure that is far more expensive to repair.
Is there a core charge for this part?
No, there is no core charge. You can keep your old part without the hassle of returning it, making the process simpler and more convenient for you.