DTC U2106: Lost Communication With Transmission Control Module (TCM): Description

Serial data on the CAN bus is transferred at a rate of 125 kilobytes-1 megabytes per second to ensure "real-time" response is maintained between Engine Control Module (ECM), Electronic Brake/Traction Control Module (EBTCM), and Transmission Control Module (TCM). When ignition switch is turned to ON position, modules begin to transmit data between each other. Each message sent on this data line has a unique identifier to classify the content and a priority assignment to denote importance. With this embedded information, only those modules on the CAN bus that have access to the message can receive the message. When more than one module on the network trys to transmit simultaneously, the message with highest priority gets access first.

The CAN bus circuit is continuously monitored by each module once ignition switch is turned to ON position. The ECM and EBTCM monitor received messages from TCM for corruption or missing messages. DTC U2106 will be set if ECM and/or EBTCM does not receive a message back from TCM 3 seconds after initialization, or if the message is corrupted. If ECM sets DTC U2106, SERVICE ENGINE SOON light on the second consecutive drive cycle that the diagnostics run and fail. If EBTCM sets DTC U2106, a malfunction DTC is stored, traction control system is disabled, and traction control indicator light will be illuminated.

A current DTC U2106 in ECM will clear when conditions for setting DTC are no longer present and ECM will turn off CHECK ENGINE SOON light after 3 consecutive drive cycles, ECM battery voltage is interrupted, or a scan tool is used to clear DTCs. A history DTC U2106 in ECM will clear after 40 consecutive warm-up cycles, if no failures are present by this diagnostic or any other emission-related diagnostic.

A current DTC U2106 in EBTCM will clear when conditions for setting DTC are no longer present, or a scan tool is used to clear DTCs. A history DTC U2106 in EBTCM will clear after 100 consecutive warm-up cycles with no malfunction detected.