RAM 1500 Van V6-239 3.9L Magnum (1995)
Overdrive Switch: Description and Operation
CONSTRUCTION
Automatic transmission equipped vehicles have an overdrive switch. The operator disables or enables overdrive when the switch is depressed.
The overdrive system consists of a switch connected to the Powertrain Control Module (PCM) and an overdrive ON/OFF indicator lamp.
OPERATION
If overdrive is currently enabled, it is disabled when the operator depresses the overdrive switch. Conversely, if the operator already disabled
overdrive, it is enabled when the switch is depressed.
Circuit T6 from the overdrive switch connects to cavity 10 of the PCM and provides the overdrive signal. Circuit Z1 provides ground for the
switch. The grounding point for circuit Z1 is on the instrument panel above headlamp switch.
In the START and RUN position, the ignition switch connects circuit A1 from fuse A7 in the Power Distribution Center (PDC) with circuit A21.
Circuit A21 connects to the bus bar in the fuse block that powers circuit G5. Power for the lamp is supplied by circuit G5 from fuse 17 in the fuse
block. The PCM turns the overdrive ON/OFF indicator lamp ON or OFF by providing a ground for the lamp on circuit T61.
