U0101: Lost communication with TCM
Drive carefully. Get it checked within a week or two.
Can I drive with U0101?
Yes, but drive carefully and get it checked soon. Vehicle lost contact with transmission computer; transmission will lock in safe limp gear.
What does U0101 mean?
U0101 stands for Lost Communication with TCM (Transmission Control Module).
Symptoms you may notice
- Multiple warning lights on dashboard simultaneously (ABS, CEL, Airbag)
- Speedometer or instrument cluster needles bouncing or freezing
- Transmission may shift harshly or default to safe limp gear
How much does it cost to fix?
Repair costs for code U0101 depend on the specific underlying root cause, ranging from simple DIY checks to component replacement. The table below lists the most common causes and rough price ranges in USD:
- Blown transmission module fuse or weak relay
- Low battery voltage during starting
- Corroded TCM connector or damaged harness
- Defective Transmission Control Module
What to do next
- Check transmission fuses in the underhood fuse box.
- Inspect battery voltage (should exceed 12.4V at rest).
- Drive gently in limp mode directly to a repair shop.
Last updated: October 2026
Related codes
General guidance only, not a professional diagnosis. If the check-engine light is flashing, or the car is running rough, overheating or losing power, stop driving and get help.
About this code
Code U0101 means modules across the vehicle can no longer communicate with the Transmission Control Module (TCM). The transmission will typically default to 3rd gear limp mode to prevent mechanical damage. You can drive slowly to a repair shop.