What Does U0101 Mean?
The requesting module has lost communication with the transmission control module (TCM). This prevents proper coordination between engine and transmission systems.
Safety Warning
May cause transmission to remain in limp mode or default gear. Vehicle may experience harsh shifting or fail to shift properly, creating unsafe driving conditions.
Common Causes
30%
Failed or failing transmission control module (TCM)
25%
Open or damaged CAN bus wiring to transmission control module
20%
Loss of power supply to TCM due to blown fuse or wiring issue
15%
Corroded or damaged TCM electrical connector
10%
Poor ground connection at TCM or transmission case
Diagnostic Steps
1
Step 1: Check all fuses related to TCM power and verify voltage at TCM power supply pins (should match battery voltage)
2
Step 2: Inspect TCM connector for corrosion, moisture intrusion, or damaged pins; clean and repair as needed
3
Step 3: Verify ground circuit continuity from TCM to battery negative and clean ground connection points
4
Step 4: Check CAN bus communication lines at TCM connector for proper voltage (~2.5V on each line with ignition on)
5
Step 5: Test TCM by swapping with known good unit if available, or check for software updates and TSBs
Estimated Repair Cost
$150 - $2,200
Parts + labor, varies by vehicle and location
The requesting module has lost communication with the transmission control module (TCM). This prevents proper coordination between engine and transmission systems.
The most common cause of U0101 (Lost Communication with TCM) is: Failed or failing transmission control module (TCM)
Typical repair costs for U0101 range from $150 to $2,200, depending on the vehicle, location, and whether you do it yourself or go to a shop.
May cause transmission to remain in limp mode or default gear. Vehicle may experience harsh shifting or fail to shift properly, creating unsafe driving conditions.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to U0101 to identify the root cause.
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Quick Info
Category
Network
System
Transmission Control
Difficulty
Type
Generic (SAE)
Recommended Tools
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