US Patent 9366336 Transmission service warm-up feature

A service warm-up feature warms transmission fluid to normal operating temperature faster than normal idle without requiring continuous technician attention. This facilitates checking the transmission fluid level. The feature increases the warm-up rate by commanding an increased line pressure and an increased idle speed, which causes more heat to be generated as the fluid flows through restrictions at an increased flow rate with an increased pressure drop. The warm-up rate may be further increased by holding the turbine shaft stationary to increase torque converter heat generation. Various precautions prevent accidental vehicle movement.