Circuit Description
WARNING: This page does not describe the selected car, but rather 14 other vehicles, including the 1998 GMC Savana Special, 1998 GMC Savana Camper Special, 1998 GMC Savana, 1998 Chevrolet RV Cutaway, and 1998 Chevrolet Cutaway. However, it is still accessible from the selected car via links, so may be relevant.
VCM monitors difference between engine speed and transmission output speed. VCM calculates turbine shaft speed and TCC slip speed by using inputs from input speed sensor, output shaft speed sensor and other transmission components. In "D3" with TCC engaged, engine speed should closely match transmission output speed. In "D4" with TCC engaged, TCC slip speed should be -25 to 30 RPM. DTC P1870 will set if VCM detects excessive TCC slip when TCC is engaged.