U0101: How to Diagnose & Fix — Lost Communication with TCM
8 vehicles · 7 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 and SKREEM (Sentry Key Remote Entry Module) fail, preventing the vehicle from starting or causing intermittent no-start conditions. The SKREEM module reads the transponder in the key and communicates with the PCM. Failure causes 'no bus' communication errors.
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
How to Fix
Replace ignition switch (Mopar 4685863AH) and/or SKREEM module (Mopar 56046149AE). New keys may need to be programmed at dealer. Try cleaning key and ignition cylinder first - cleaning the key transponder ring around the ignition cylinder resolves intermittent issues for some owners.
Sources for this issue (2)
Jeep Grand Wagoneer · 2021–2024
The Quadra-Trac transfer case encoder motor on Grand Wagoneer models fails to properly shift between 2WD, 4WD Auto, 4WD Low, and Neutral modes, leaving the vehicle stuck in a single drive mode or displaying a 'Service 4WD System' message. The BorgWarner transfer case encoder motor and position sensor can develop electrical faults or mechanical binding, particularly after exposure to water or road salt. Owners report being unable to disengage 4WD Low or experiencing grinding/clunking when attempting mode changes.
Common Symptoms
- 'Service 4WD System' warning on instrument cluster
- Transfer case stuck in 4WD Low or unable to engage
- Grinding or clunking noise during mode change attempt
- 4WD selector buttons unresponsive on center console
- Vehicle behaves as though in wrong drive mode for road conditions
How to Fix
Replace the transfer case encoder motor assembly (Mopar part reference BorgWarner 4406/4407 encoder motor). A TSB may require updated transfer case control module software reflash via dealer scan tool. Full transfer case replacement may be needed if internal damage has occurred from prolonged incorrect engagement.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine Mopar 68679351AA active transfer-case shift motor/actuatorOEMMopar 68679351AA
Active shift-motor replacement when TSB 21-048-24 applies or service diagnostics independently confirm motor failure Fitment/availability: 2022-2024 Grand Wagoneer 3.0L/6.4L with the applicable DKA or DHR transfer-case branch; supersedes…
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Dodge Dart · 2013–2016
The 2.4L Dart paired with the Aisin 6-speed automatic experiences TCM failures that cause erratic shifting, failure to shift, and limp mode. The TCM mounted on the transmission is exposed to heat and vibration, leading to internal circuit board failures. Unlike the DDCT issues on 1.4T models, this affects the conventional automatic transmission.
Common Symptoms
- Transmission stuck in limp mode (2nd gear only)
- Erratic or harsh shifting
- Check engine light with transmission codes
- Transmission fails to shift into higher gears
- Delayed engagement when shifting from Park
How to Fix
Replace the TCM (Mopar 68164473AH or equivalent). The replacement TCM must be programmed with the VIN and transmission adaptation data at the dealer using wiTECH. Aftermarket remanufactured TCMs are available but must still be dealer-programmed. Cost is $600-$1,200 installed.
Sources for this issue (1)
Chevrolet Silverado 3500HD · 2006–2019
Mercedes-Benz AMG GT · 2019–2025
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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 8 vehicle models from 7 manufacturers: Chevrolet, Chrysler, Dodge, Ford, GMC, Jeep, Mercedes-Benz.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.