Grand Cherokee 2WD V8-318 5.2L VIN Y MFI (1994)
Overdrive Switch: Description and Operation
Circuit Operation
CIRCUIT OPERATION
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 a Light Emitting Diode (LED) which
illuminates for the overdrive ON/OFF indicator.
If overdrive is currently enabled, it is disabled when the operator depresses the overdrive switch. Also, if the operator already disabled overdrive,
it is enabled when the switch is depressed.
Circuit T9 from the overdrive switch connects to cavity C13 of the PCM and provides the overdrive signal. Circuit Z1 provides ground for the
switch.
In the RUN position, the ignition switch connects circuit A1 from fuse 8 in the Power Distribution Center (PDC) with circuit A22. Circuit A22
powers circuit F71 through fuse 12 in the junction block. Circuit F71 supplies power for the overdrive ON/OFF indicator LED. The PCM turns the
overdrive ON/OFF indicator ON or OFF by providing ground on circuit G68. Circuit G68 connects to cavity C6 of the PCM.
