Jeep 1997 Grand Cherokee Service Manual page 1262

8W - 33 - 6
DESCRIPTION AND OPERATION
VEHICLE SPEED CONTROL
The Powertrain Control Module (PCM) operates
the vehicle speed control system. The vehicle speed
control switches are located in the steering wheel.
Circuit V32 from cavity C11 of the PCM connects
to circuit V30 through the stop lamp switch. Circuit
V30 powers the vehicle speed control servo.
Circuit K95 from PCM cavity C32 connects to the
vehicle speed control switches. The switches are
wired in parallel and each contains a separate resis-
tor. The voltage level present on circuit K95 (at PCM
cavity C32) depends on which speed control switch is
selected. Circuit K4 from PCM cavity A4 supplies
ground for the speed control switches.
• When the ON/OFF switch is open, the voltage
level on circuit K95 at PCM cavity C32 has a nomi-
nal value of 5.0 volts with a range from 4.8 to 5.0
volts.
• When the ON/OFF switch closes, the voltage
level on circuit K95 at PCM cavity C32 has nominal
value of 1.51 volts with a range from 1.31 to 1.61
volts.
• When the SET switch closes, the voltage level on
circuit K95 at PCM cavity C32 has nominal value of
3.8 volts with a range from 3.6 to 3.9 volts.
• When the RESUME/ACCEL switch closes, the
voltage level on circuit K95 at PCM cavity C32 has
nominal value of 4.4 volts with a range from 4.2 to
4.5 volts.
• When the COAST switch closes, the voltage
level on circuit K95 at PCM cavity C32 has nominal
value of 2.92 volts with a range from 2.72 to 3.02
volts.
• When the CANCEL switch closes, the voltage
level on circuit K95 at PCM cavity C32 has is 0.1
volts or less.
The PCM controls the vent and vacuum functions
of the vehicle speed control servo on circuits V35 and
V36. Depending on the signal it receives from vehicle
speed control switches, the PCM either applies vac-
uum to or vents vacuum from the servo. Circuit V36
from cavity C4 of the PCM sends the vacuum signal
to the servo. Circuit V35 from cavity C5 sends the
vent signal.
Circuit L53 provides the stop lamp switch sense
input to the PCM at cavity C24. The stop lamp
switch connects circuit L53 to ground on circuit Z1.
When the brake pedal is depressed, the stop lamp
switch opens and disconnects circuits L53 and Z1,
and circuits V32 and V30. When the stop lamp
8W - 33 VEHICLE SPEED CONTROL
8W-33 VEHICLE SPEED CONTROL
switch disconnects circuits V32 and V30, power is
removed from the speed control servo.
HELPFUL INFORMATION
Circuit K4 also provides ground for some of the
engine control sensors that provide inputs to the
PCM.
VEHICLE SPEED CONTROL (DIESEL)
The Powertrain Control Module (PCM) operates
the vehicle speed control system. The vehicle speed
control switches are located in the steering wheel.
Circuit V32 from the PCM connects to circuit V30
through the stop lamp switch. Circuit V30 connects
to circuit Z2 ground. Circuit L53 from the PCM con-
nects to Circuit Z1 ground, through the stop lamp
switch.
Circuit K95 from the PCM connects to the vehicle
speed control switches. The switches are wired in
parallel and each contains a separate resistor. The
voltage level present on circuit K95 at the PCM
depends on which speed control switch is selected.
Circuit K4 from PCM supplies ground for the speed
control switches.
• When the ON/OFF switch is open, the voltage
level on circuit K95 at the PCM has a nominal value
of 5.0 volts with a range from 4.8 to 5.0 volts.
• When the ON/OFF switch closes, the voltage
level on circuit K95 at the PCM has nominal value of
1.51 volts with a range from 1.31 to 1.61 volts.
• When the SET switch closes, the voltage level on
circuit K95 at the PCM has nominal value of 3.8
volts with a range from 3.6 to 3.9 volts.
• When the RESUME/ACCEL switch closes, the
voltage level on circuit K95 at the PCM has nominal
value of 4.4 volts with a range from 4.2 to 4.5 volts.
• When the COAST switch closes, the voltage
level on circuit K95 at the PCM has nominal value of
2.92 volts with a range from 2.72 to 3.02 volts.
• When the CANCEL switch closes, the voltage
level on circuit K95 at the PCM is 0.1 volts or less.
Circuit L53 and V32 provide stop lamp switch
sense input to the PCM. When the brake pedal is
depressed, the stop lamp switch opens and discon-
nects circuits L53 and Z1, and circuits V32 and V30
indicating brakes are applied.
HELPFUL INFORMATION
Circuit K4 also provides ground for some of the
engine control sensors that provide inputs to the
PCM.
ZG