Jeep 1997 Grand Cherokee Service Manual page 1255

ZG
8W-31 TRANSMISSION CONTROL SYSTEM
DESCRIPTION AND OPERATION
GOVERNOR PRESSURE SENSOR . . . . . . . . . . . 7
OUTPUT SHAFT SPEED SENSOR . . . . . . . . . . . 7
OVERDRIVE SWITCH . . . . . . . . . . . . . . . . . . . . . 7
DESCRIPTION AND OPERATION
OVERDRIVE SWITCH
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 con-
nected 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 Cen-
ter (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 indica-
tor LED. The PCM turns the overdrive ON/OFF indi-
cator ON or OFF by providing ground on circuit G68.
Circuit G68 connects to cavity C6 of the PCM.
TRANSMISSION CONTROL RELAY
The transmission control relay powers the over-
drive solenoid, torque convertor clutch solenoid, and
variable force solenoid. All three solenoids are
molded together.
When the ignition switch is in the START or RUN
positions, it connects circuit A1 from fuse 8 in the
Power Distribution Center (PDC) to circuit A21. Cir-
cuit A21 powers circuit F99 through fuse 18 in the
PDC. Circuit F99 powers the coil side of the elec-
tronic transmission relay. The Powertrain Control
Module (PCM) provides ground for the relay on cir-
cuit T66. Circuit T66 connects to cavity B30 of the
PCM.
When the PCM grounds the relay, the relay con-
tacts connect circuit F92 from fuse 17 in the PDC to
circuit T20. Circuit T20 powers the solenoids.
8W - 31 TRANSMISSION CONTROL SYSTEM
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INDEX
SHIFT INTERLOCK . . . . . . . . . . . . . . . . . . . . . . . 7
TRANSMISSION CONTROL RELAY . . . . . . . . . . 7
TRANSMISSION SOLENOID ASSEMBLY . . . . . . 7
TRANSMISSION TEMPERATURE SENSOR . . . . 8
TRANSMISSION SOLENOID ASSEMBLY
The Torque Convertor Clutch (TCC) solenoid, over-
drive solenoid and variable force solenoid are molded
together. Circuit T20 from the electronic transmis-
sion relay supplies power for the solenoids. The Pow-
ertrain Control Module (PCM) operates each solenoid
individually by providing ground for each solenoid on
separate circuits.
• The PCM provides ground for the TCC solenoid
on circuit T22. Circuit T22 connects to cavity B11 of
the PCM.
• The PCM supplies ground for the overdrive sole-
noid on circuit T60. Circuit T60 connects to cavity
B21 of the PCM.
• On circuit T59, the PCM provides ground for the
variable force solenoid. Circuit T59 connects to cavity
B8 of the PCM.
SHIFT INTERLOCK
The shift interlock prevents the operator from
shifting the vehicle out of PARK unless the brake
pedal is pressed. When the ignition switch is in the
START or RUN position, circuit A21 feeds circuit F87
through fuse 5 in the junction block. Circuit F87
splices to power the shift interlock.
When the brake pedal is not depressed, the stop
lamp switch provides ground for interlock by connect-
ing circuit L53 to ground. When grounded, the inter-
lock prevents shifting the transmission out of PARK.
When the brake pedal is pressed, the stop lamp
switch disconnects circuit L53 from ground.
OUTPUT SHAFT SPEED SENSOR
The output shaft speed sensor generates a signal
indicating the speed of the transmission output shaft.
Circuits T13 and T14 connect the sensor to the Pow-
ertrain Control Module (PCM). Circuit T13 connects
to cavity B25 of the PCM. Circuit T14 connects to
cavity B28.
GOVERNOR PRESSURE SENSOR
The governor pressure sensor supplies the trans-
mission pressure input to the Powertrain Control
Module on circuit T25. Circuit T25 connects to cavity
8W - 31 - 7
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