U0101 on GMC: How to Diagnose & Fix
Lost Communication with TCM
1 GMC model · 1 documented issue · 1 critical · $500-$3,500 repair
U0101 on GMC by model: symptoms, diagnosis and fix
The Allison 1000 transmission paired with the Duramax diesel in 2008-2015 Sierra 3500HD trucks has a high failure rate for the Transmission Control Module (TCM). A class action suit was filed covering these years. Additional issues include input/output speed sensor failures causing no-forward/reverse conditions, and certain 2012 trucks built with incorrect thrust bearings.
Common Symptoms
- Intermittent no forward or reverse movement
- Flashing PRNDL display
- Range Shift Inhibited message
- Harsh or delayed shifts
- Transmission noise or whine
- Check engine light with transmission codes
How to Fix
Sources for this issue (1)
U0101 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does U0101 mean on a GMC?
U0101 stands for "Lost Communication with TCM." This is a network communication code meaning a control module on the vehicle's data bus has lost communication with the Transmission Control Module (TCM). Modern vehicles use a shared data network (commonly CAN bus) so modules can exchange information; when the TCM stops responding or its messages disappear, other modules set this code. Because the transmission relies on this communication to shift properly, the vehicle may go into 'limp' mode, hold one gear, or refuse to shift normally. It generally indicates a wiring, power, ground, or connector problem on the network — or a failed TCM itself — rather than an internal mechanical transmission fault. On GMC it is documented across 1 model: Sierra 3500HD.
What are the most common causes of U0101?
The most common causes of U0101 are: Damaged, corroded, or loose TCM wiring or connectors, Open or short in the CAN bus data wiring, Blown fuse or lost power/ground to the TCM, Corrosion or water intrusion at the TCM connector, Faulty Transmission Control Module, Another faulty module dragging down the data bus, Poor ground connection in the network. The specific cause varies by vehicle.
How much does it cost to fix U0101 on a GMC?
Published repair estimates on GMC range from $500 to $3,500 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.