The U0101 DTC can be found in many vehicles, including Cadillac, Chevrolet, GMC, Buick, and Nissan. It means that the transmission control module is not communicating with one or more modules that are connected with it through the CAN bus/controller area network system.
How Serious is the Code?
The transmission problems associated with a U0101 diagnostic trouble code can be fairly severe, to the point that your vehicle may be locked in Limp Mode that will restrict the transmission to a single gear (often 2nd or 3rd).
Symptoms of a U0101 include:
- The transmission will not change gear
- Transmission will not shift out of a forward gear
- Limp mode
- Damaged wiring
- Damaged connectors
- Damage to ground connection
- Failed TCM
How to Diagnose the Code?
The first step to figuring out what is causing a U0101 OBDII code, is to check the manufacturer’s TSB database to see if there is a known cause or solution. If none are found, then the wiring and connectors in the CAN bus system will need to be checked for signs of damage and corrosion. All of the ground connections will need to be checked as well. Any fuses or relays that are related to the TCM will need to be tested. If no problems are found at this point, the TCM itself will need to be checked.
What Repairs Will Fix U0101?
- Repair damaged wiring or connectors
- Repair ground connections
- Replace TCM