U0101 on Mercedes-Benz: How to Diagnose & Fix
Lost Communication with TCM
1 Mercedes-Benz model · 1 documented issue · 1 critical
U0101 on Mercedes-Benz by model: symptoms, diagnosis and fix
On the X290 four-door AMG GT (GT 43 / GT 53), the transmission wiring harness can be routed incorrectly so that the electrical connector sits where it is exposed to water and road spray. The connector corrodes, and the corroded contacts can short-circuit — which Mercedes-Benz itself describes as increasing the risk of fire, and which can also strand the car with transmission fault messages. NHTSA campaign 22V533000 covered 2019-2022 GT 53 and 2021-2022 GT 43. That remedy did not hold: campaign 24V445000 was opened afterward for 2019-2025 GT 53 and 2021-2024 GT 43 because the harness connection 'might not have been correctly wired during a prior recall repair or during production' — meaning cars that already had the first recall performed can still be defective. This is a four-door X290 issue tied to the 9G-TRONIC installation and does not transfer to the C190 two-door's rear transaxle DCT.
Common Symptoms
- Transmission fault or limp-home message
- Intermittent shifting faults that come and go with weather
- Burning-plastic smell from under the vehicle
- Corroded green residue on transmission harness connector
How to Fix
Free recall remedy. Under 22V533000 the dealer inspects and repairs the connector, reroutes the harness and installs a retaining bracket. Under the superseding 24V445000 the dealer replaces the two-part wiring harness and the connector outright — the more durable fix. Do not accept 'recall already done' as closing this out on a GT 43/GT 53: check the VIN specifically against 24V445000, since that campaign exists precisely to catch cars the earlier repair left wrong. If the car is showing intermittent transmission faults, have the connector inspected for green corrosion before any transmission control unit is condemned.
Sources for this issue (2)
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 Mercedes-Benz?
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 Mercedes-Benz it is documented across 1 model: AMG GT.
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 Mercedes-Benz?
Repair costs vary widely with the root cause and Mercedes-Benz model; each issue on this page carries its own estimate where one is published.
Looking for U0101 on a different make?
View U0101 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.