U0101: How to Diagnose & Fix — Lost Communication with TCM
7 vehicles · 6 makes · $200-$3,500 repair
How to diagnose and fix U0101: most-reported vehicles
Ranked by owner reports. Each card gives the symptoms, how to confirm the cause, the fix, parts and sources for that vehicle.
Chrysler Town & Country · 2008–2016
The ignition switch inside the Wireless Ignition Node (WIN) fails, preventing the vehicle from starting or causing intermittent no-start conditions. The WIN contains the ignition switch, reads the transponder in the key fob (FOBIK) for the immobilizer, and communicates with the PCM. Failure causes 'no bus' communication errors. On 2008-2010 vans built through June 17, 2010, a worn switch can also let the key slip out of Run and shut the engine off while driving (NHTSA recalls 11V-139 and 14V-373).
Common Symptoms
- Vehicle cranks but won't start
- Security light flashing on dashboard
- Key won't turn in ignition
- Intermittent no-start that resolves after waiting
- Engine shuts off while driving if the key is bumped (2008-2010 recall)
How to Fix
Check the VIN for NHTSA recalls 11V-139 / 14V-373 (Chrysler campaigns L02/L25, later R03): on 2008-2010 vans built January 26, 2007 to June 17, 2010, dealers replace the WIN ignition switch and key fobs free. Out of the recall, replace the WIN module; the new WIN and keys must be programmed to the vehicle at a dealer or an equipped shop. First rule out a weak fob battery and a low vehicle battery.
Call to confirm they can assess your vehicle and perform the stated work. Search results do not confirm qualification, eligibility or coverage.
Sources for this issue (2)
Ford Fiesta · 2011–2015
The DPS6 PowerShift's Transmission Control Module, mounted on the transmission and exposed to heat, fails electrically. The car suddenly loses drive while moving, will not start, drops into limp mode, or the cluster throws a transmission fault with stored U0101 (Lost Communication with TCM). Ford acknowledged it with Customer Satisfaction Program 14M02, extending TCM coverage on 2011-2015 Fiestas to 10 years / 150,000 miles. A replacement TCM must be programmed to the car by a Ford dealer, and parts shortages in 2019-2021 left owners waiting weeks.
Common Symptoms
- Sudden loss of transmission engagement while driving
- Intermittent no-start or no-crank
- Transmission fault / wrench warning on cluster
- Lack of power, stuck in a gear or limp mode
- U0101 lost communication with TCM
How to Fix
Replace the TCM and reprogram it to the vehicle (dealer only for the initial flash). Covered free under Ford program 14M02 for 10 yr/150k mi from warranty start (coverage transfers to later owners); outside that window a TCM is roughly $600-$1,200 installed. Verify U0101/P0700 rather than assuming clutches — if the TCM is not the cause, 14M02 does not pay.
Call to confirm they can assess your vehicle and perform the stated work. Search results do not confirm qualification, eligibility or coverage.
Sources for this issue (3)
GMC Sierra 3500HD · 2008–2019
The Allison 1000 transmission paired with the Duramax diesel in Sierra 3500HD trucks has a high failure rate for the Transmission Control Module (TCM). GM issued technician information (PIP4560 series) on Allison TCM parts restrictions. Additional issues include input/output speed sensor failures causing no-forward/reverse conditions, and certain 2012 trucks built with incorrect thrust bearings (GM Customer Satisfaction Program 14043).
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
Scan for transmission and U-codes and check TCM connectors and input/output speed sensor wiring before replacing the TCM. For 2012 trucks, ask a dealer whether GM Customer Satisfaction Program 14043 (thrust bearing replacement) was completed; the free repair window ended March 31, 2016.
Call to confirm they can assess your vehicle and perform the stated work. Search results do not confirm qualification, eligibility or coverage.
Sources for this issue (2)
Chevrolet Silverado 3500HD · 2006–2019
Dodge Dart · 2013–2016
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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?
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.
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?
Repair costs for U0101 range from $200 to $3,500, depending on the vehicle and root cause.
Which vehicles are affected by U0101?
Au7o has documented U0101 across 7 vehicle models from 6 manufacturers: Chevrolet, Chrysler, Dodge, Ford, GMC, Mercedes-Benz.
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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.