What Does Code U0100 Mean? U0100 stands for “Lost Communication with ECM/PCM.” The Engine Control Module (ECM) is the computer responsible for controlling the engine. The ECM communicates with other ...

For example, an older vehicle may use an ECM and a TCM (transmission control module) to accomplish many of the same tasks as a PCM does in a newer car. The PCM and ECM perform similar duties when ...