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.
The 4WD low circuit consists of a transfer case switch, an indicator light and wiring. When 4WD low is engaged, voltage to VCM changes from ignition voltage to zero. The 4WD low switch signal corrects transmission output shaft speed signal to VCM. This signal compensates for transfer case gear reduction. VCM uses transmission output shaft speed signal to adjust shift points, line pressure and TCC apply and release. DTC P1875 will set if VCM detects a continuous open or short to ground in 4WD low circuit.