This post is part of our “Deep Delve” series, where we’ll focus on one part at a time. The goal of these posts is to provide our customers with the knowledge they need to make informed decisions about their vehicle. We can’t reveal all the knowledge we have about these parts, but hopefully the information below will help you find the issue in your vehicle.
If you own a GMC or Chevrolet truck equipped with the Allison 1000 6-speed automatic transmission, chances are you’ve heard about the notorious issues with the Transmission Control Module (TCM). For years, these modules have been plagued with high failure rates—and worse, zero support from the dealership network. At XeMODeX, we recognized the scope of this problem early on and committed our R&D resources to solve it. Today, we’re proud to offer a reliable, high-success-rate repair service for these hard-to-find TCMs.
The Problem: A Failing Module with No Fix in Sight
The affected modules are found on 2006–2015 GM trucks equipped with the Allison transmission, including models such as:
- Chevrolet Silverado 2500HD / 3500HD
- GMC Sierra 2500HD / 3500HD
- And other GM vehicles with the Duramax diesel and Allison transmission pairing
Over time, these TCMs developed a reputation for failure, leaving many vehicles stuck in limp mode—or worse, inoperable. Unfortunately, the issue was compounded by a lack of available replacements. For several years, these modules were completely unavailable from GM dealers, and alternative repair options simply didn’t exist.
Common Symptoms of a Failing Allison TCM
Drivers and technicians commonly report the following issues:
- Transmission stuck in limp mode
- Hard shifting or failure to shift
- No communication with the TCM via scan tools
- Check engine light (CEL) illumination
- “PRNDL” gear position indicator is not displayed in the instrument cluster
- Transmission goes to neutral when driving
- Transmission is stuck in third gear
- Transmission suffers from erratic shifting
Frequent diagnostic trouble codes (DTCs) include:
- U0101 – Lost Communication with Transmission Control Module
- P0700 – Transmission Control System Malfunction
- P0802 – Transmission Control System MIL Request Circuit
A Challenge Accepted by XeMODeX
In 2022, we began receiving a growing number of requests from frustrated customers asking if we could do anything about these modules. With no one offering a viable repair, our R&D team took on the challenge—knowing it would be neither easy nor cheap. We invested substantial time, capital, and technical effort into understanding the intricate failure modes of these TCMs. Unlike simpler modules, these units feature a hybrid of microelectronic and mechanical failure points that make diagnostics and repair extremely difficult. But giving up wasn’t an option.
Innovation First: The XeMODeX Solution
After extensive research and development, XeMODeX became the first company to offer a reliable repair service for GM’s Allison TCMs. We didn’t just fix the most common failures—we developed a comprehensive repair procedure that brings modules back to full working condition.
Today, our repair success rate for these modules sits at 99%, thanks to our advanced in-house testing equipment, proprietary repair methods, and technician expertise. This is not a patch job—this is a full, professional-grade restoration.
Imitated, But Never Equaled
Since we launched our repair service, other shops have tried to replicate it. But XeMODeX was the first, and we continue to lead in terms of quality, and long-term reliability. Our process is not something easily duplicated—it was born from deep technical know-how and a commitment to solving a problem no one else could.
Why Choose XeMODeX?
- Industry-Leading Repair Accuracy: 99% success rate
- Fast Turnaround: We minimize downtime
- Real Solutions: No guesswork or “reflow” hacks—just proper repair
- Proven Track Record: Trusted for over 18 years in advanced electronics repair
GM’s Allison TCM issues left thousands of trucks sidelined. At XeMODeX, we turned that frustration into innovation. Our repair solution isn’t just a fix—it’s proof that when others walk away, we get to work.
Need help with your TCM?
Choose the company that brought the first real solution to market. Check out our GM TCM repair service on our website www.xemodex.com
For GMC trucks
US Customers: https://xemodex.com/us/product/transmission-control-module-repair-for-gmc/
Canadian Customers: https://xemodex.ca/ca/product/transmission-control-module-repair-for-gmc/
For Chevrolet trucks
US Customers: https://xemodex.com/us/product/transmission-control-module-repair-for-chevrolet/
Canadian Customers: https://xemodex.ca/ca/product/transmission-control-module-repair-for-chevrolet/
