U0101 on GMC
Lost Communication with TCM
U0101 on GMC vehicles indicates lost communication with tcm. Au7o has documented this code across 1 GMC model — most commonly on Sierra 3500HD. 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. Typical repair costs on GMC range from $500 to $3,500, depending on the specific model and root cause.
Common Causes of U0101
- •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
U0101 on GMC by Model
GMC Sierra 3500HD(1 issue)
- Allison 1000 Transmission Control Module and Sensor Failures2008-2019
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.
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View U0101 across all makes →Frequently Asked Questions
What does U0101 mean on 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 specifically, this code is documented across 1 model.
What causes U0101 on GMC vehicles?▼
Common causes on GMC: 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. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix U0101 on a GMC?▼
Repair costs on GMC range from $500 to $3,500, depending on the specific model and root cause.
Which GMC models have U0101 documented?▼
Au7o has documented U0101 on 1 GMC model: Sierra 3500HD.