Restore Your Truck’s Shifting Performance
Is your 2001-2005 GMC Sierra or Chevrolet Silverado HD experiencing erratic shifting, getting stuck in one gear, or showing a check engine light with transmission-related fault codes? These are classic signs of a failing Transmission Control Module (TCM). The TCM is the electronic brain of your Allison transmission, and when it fails, it can sideline your powerful workhorse. This replacement TCM, part number 15169835, is the definitive solution to get your truck back to operating with the reliability and precision you depend on.
Unlike a generic module from a parts store, this unit is delivered to you fully programmed to your vehicle’s specific Vehicle Identification Number (VIN). We load the latest GM-authorized software updates, which often correct factory-level shifting issues and improve transmission longevity. This VIN-matching process is critical for ensuring seamless communication between the TCM, the Engine Control Module (ECM), and the transmission itself, eliminating the need for an expensive trip to the dealership for programming.
From the Diagnostic Bay
We had a 2004 Silverado 2500HD come into the shop with the classic “limp mode” complaint. The driver said it would shift hard from 1st to 2nd, and then get stuck in 3rd gear, making it dangerously slow on the highway. We scanned it and pulled codes P0700 (Transmission Control System Malfunction) and U0100 (Lost Communication With ECM/PCM). After checking the wiring harness and connectors for any obvious damage—a common issue on these trucks—we found everything to be intact. The symptoms pointed directly to an internal failure of the TCM. Instead of a costly dealer replacement, the owner opted for one of our pre-programmed modules. We provided the VIN, received the new module two days later, and installed it in under 30 minutes. The truck immediately started and shifted perfectly through all gears on the test drive. No more codes, no more limp mode—just a happy customer back on the road.
Common Symptoms of a Failing Allison TCM
- ✔ Harsh or delayed shifting between gears.
- ✔ The transmission getting stuck in one gear (limp mode).
- ✔ Illumination of the Check Engine Light or Transmission Warning Light.
- ✔ Diagnostic trouble codes (DTCs) related to the transmission, such as P0700, P0751, P0756, or U-series communication codes.
- ✔ Inaccurate or erratic gear indicator display on the dashboard.
- ✔ A complete loss of drive, where the truck won’t move in any gear.
- ✔ Unexplained battery drain, as a faulty module can fail to shut down properly.
The Importance of a Programmed 2001-2005 Sierra 2500 TCM
The Allison 1000 series (RPO code M74) 5-speed automatic transmission found in these GM HD trucks is a legendary piece of equipment, but its performance is entirely dependent on the TCM. The module processes data from sensors throughout the vehicle—like vehicle speed, engine RPM, and throttle position—to make instantaneous decisions about when to shift, how firmly to engage the clutches, and when to lock up the torque converter. When you install a 2001-2005 Sierra 2500 TCM that isn’t programmed to your truck’s VIN, it won’t have the correct information about your vehicle’s specific configuration (like axle ratio and tire size), leading to poor performance and potential transmission damage. Our service eliminates this risk by handling all the programming for you before the part ever leaves our facility.
Simple Installation Process
This TCM is located on the driver’s side of the engine bay, mounted to the fan shroud for cooling. Installation is a straightforward process for a DIY mechanic or any professional technician. Simply disconnect the battery, unplug the electrical connectors from the old TCM, unbolt it from the fan shroud, and install the new one in its place. Reconnect the connectors and the battery, and you’re ready to go. No additional programming or relearn procedures are required.
Guaranteed Fitment
This module is a direct replacement for vehicles equipped with the 5-speed Allison automatic transmission (option code M74). Please verify fitment for your specific truck:
- 2001-2005 GMC Sierra 2500 / 3500 Pickup (with Allison AT, 5 speed, opt M74)
- 2001-2005 Chevrolet Silverado 2500 / 3500 Pickup (with Allison AT, 5 speed, opt M74)
Cross-Reference Part Numbers (SERV NO):
This module replaces the following service numbers: 15768288, 15071240, 15163072, 15163073, 15169833, 15169834, 15169835, 15183963, 15187103, 15187104, 29537441, 09385220, 09387820.
Frequently Asked Questions
How do I provide my VIN for programming?
After you complete your purchase, you can add your 17-digit VIN to the notes section of your order or send us a message with your order number and VIN. We cannot ship your part until we receive this information.
Is any additional programming needed after installation?
No. This 2001-2005 Sierra 2500 TCM arrives fully programmed with the latest GM software matched to your VIN. It is a true plug-and-play solution, requiring no further action from a dealer or mechanic.
Will this fix my truck’s limp mode issue?
If the limp mode is caused by an internal failure of the TCM, then yes, this part is the correct fix. It is one of the most common failure points for these symptoms. However, you should always verify that the wiring harness and connectors are in good condition, as damaged wiring can cause similar issues.
Where is the TCM located on my truck?
On 2001-2005 GM HD trucks with the Allison transmission, the TCM is a silver metal box with cooling fins, bolted to the driver’s side of the radiator fan shroud inside the engine bay.
Do I need to send my old part back?
No core charge or return is required for this part. You can keep or dispose of your old module at your convenience.