Which of the following is a main function of the transmission control module (TCM)?

The transmission control module (TCM) plays a crucial role in the operation of an automatic transmission by managing the gear shifting process. One of its primary functions is to control gear shifts based on various factors, including vehicle speed, load conditions, and engine performance. By utilizing input from various sensors, the TCM can determine the optimal timing for shifting gears to ensure smooth acceleration, fuel efficiency, and overall performance of the transmission system.

In terms of vehicle operation, the TCM collects data from sensors that monitor aspects such as throttle position and vehicle speed, allowing it to execute gear shifts appropriately. This not only enhances driving comfort by providing smoother transitions between gears but also contributes to the engine's efficiency by optimizing the power band under different driving conditions.

The other choices pertain to functions that are handled by different components of the vehicle. Regulating the engine's air-fuel mixture is primarily the responsibility of the engine control module (ECM). Monitoring tire pressure is typically managed by a tire pressure monitoring system (TPMS). Filtering transmission fluid is a function carried out by the transmission filter, which is separate from the control mechanisms governed by the TCM. Thus, the primary function of controlling gear shifts aligns specifically with the competencies of the TCM.