U0101 on Toyota Corolla E170: Lost Communication With TCM

Short answer: U0101 means “Lost Communication With TCM”. The car’s computer has found a fault in the Network system and turns on the Check engine light (MIL). First check: check battery voltage and the main fuses.

Standard OBD-II code Same meaning on all cars (SAE J2012). Not checked against this car’s factory manual.

Code

U0101

System

Network

Dashboard light

Check engine light (MIL)

Applies to

Generic OBD-II meaning. Not every code is used by this car.

Confidence

medium (generic OBD-II definition, not checked against the factory manual for this car)

Source

obd-codes.com

Symptoms and when it is set

1. Check engine light on
2. Vehicle will not shift
3. Vehicle stays in one gear (usually 2nd or 3rd)

Likely causes

1. Typically the causes for this code to set are
2. Open in the CAN bus + circuit
3. Open in the CAN bus - circuit
4. Short to power in either CAN bus circuit
5. Short to ground in either CAN bus circuit
6. Rarely - faulty control module

What to check, in order

1. Check battery voltage and the main fuses
2. Check the connectors of the module named in the code
3. Read codes from all modules with a capable scanner

Related on this car

• All fault codes for this car
• Warning lights
• Where the parts are (parts map)
• Common problems

Same code on other cars

• U0101 · Toyota Passo (1st gen)
• U0101 · Toyota Corolla (10th gen, E140)
• U0101 · Honda City (5th gen, GM2)
• U0101 · Honda Civic (10th gen, FC)
• U0101 · Suzuki Wagon R (Pakistan, K10B)
• U0101 on all cars compared

← U0100

Clearing the code does not fix the fault. If it comes back, the problem is still there. For brakes, airbags and steering, see a trained mechanic.