U0100 Toyota Code - Lost Communication with Engine Control Module

U0100 Toyota Code - Lost Communication with Engine Control Module |Code U0100 Toyota Possible Causes NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes. Faulty Controller Area Network (CAN) Communication System Faulty Control Module Control Module harness is open or shorted Control Module circuit poor electrical connection |Code U0100 Toyota Tech Notes When there are problems with the way different systems in a vehicle communicate with each other using a technology called Controller Area Network (CAN) communication, Diagnostic Trouble Codes (DTC) are displayed. These codes can be caused by issues with the main bus or branch of the communication network, or with the Electronic Control Units (ECUs) and sensors that make up the different systems. If you see code for both the CAN communication problems and internal or power source problems at the same time, you should focus on fixing the internal or power source problems first.