Cruise control is a speed control system that maintains
a desired vehicle speed under normal driving conditions. However, steep grades
up or down may cause variations in the selected speeds. The electronic cruise
control system has the capability to CRUISE, COAST, RESUME SPEED, ACCELERATE,
and TAP-UP or TAP-DOWN.
The main parts of the cruise control system are:
| • | The cruise control module assembly |
| • | The function control switches |
| • | The cruise control release switch |
| • | The stoplamp switch assembly |
| • | The vehicle speed sensor |
The cruise control system uses the cruise control module assembly to
maintain the desired vehicle cruise speed and operation. The cruise control
module assembly has a controller and an electric stepper motor to vary the
throttle in each different cruise control mode. Two important components
in the module assembly help to do this. The first is the electronic controller
and the second is an electric stepper motor. The controller monitors vehicle
speed and operates the stepper motor. The stepper motor operates in response
to the controller, to maintain the desired cruise speed. The electric stepper
motor moves a strap that is attached to the cruise control cable which moves
the throttle linkage. The cruise control module assembly contains a low
speed limit which will prevent system engagement below a minimum speed
of 40 km/h (25 mph). The module assembly is not serviceable.
The operation of the controller is controlled by the function control
switches located on the cruise control lever. The cruise control function
control switches includes the ON/OFF, SET/COAST, R/A (resume/accelerate)
and CANCEL switch. The switch assembly provides driver control of the cruise
control system.
The cruise control release switch, stoplamp switch and cancel switch
are used to disengage the cruise control. A release switch assembly and a
stoplamp switch assembly are mounted on the brake pedal bracket and the
cancel switch is located on the cruise control lever. To disengage the system
the driver either presses the brake pedal or activates the cancel switch.
The speed of the vehicle at brake actuation will be stored in the memory
of the cruise module.
The vehicle speed sensor (VSS) is mounted to the automatic transaxle
assembly and produces an AC signal. The frequency of this signal is proportional
to the speed at which the automatic transaxle assembly output shaft rotates,
which in turn is proportional to the speed of the vehicle. The AC signal
is supplied to the powertrain control module (PCM). The PCM converts the
number of pulses per mile per second to determine vehicle speed. The signal
is then sent to the cruise control module assembly and speedometer assembly
at a rate of 4000 pulses per mile.
With cruise control, you can maintain a speed of about 40 km/h (25 mph)
or more without keeping your foot on the accelerator. When the driver turns
off the on/off switch, ignition switch, or the cancel switch, the cruise
control turns off. The vehicle speed stored in the memory of the cruise
module will be lost.
Ignition positive voltage is supplied from the cruise control
fuse, to the cruise control module. The cruise control module is grounded
to the chassis. When the cruise control ON/OFF switch is on, ignition positive
voltage is applied to the cruise on switch signal terminal of the cruise
control module. If the driver has not pressed the brake pedal, ignition
positive voltage is supplied through the cruise control release switch,
to the cruise control brake pedal switch signal terminal of the cruise control
module. When the driver presses the brake pedal, battery positive voltage
is supplied from the stop lamp fuse, through the closed stop lamp switch
to the stop lamp switch signal terminal of the cruise control module. When
the SET/COAST is pressed on the control switch, ignition positive voltage
is applied to the set/coast switch signal terminal of the cruise control
module. When pressing the R/A (resume/accelerate) on the control switch,
ignition positive voltage is applied to the resume/accelerate
switch signal terminal of the cruise control module.
The cruise control module receives a vehicle speed signal input from
the powertrain control module (PCM). In operation, the voltage varies between
0 V and 5 V.
The cruise control module, cruise indicator control terminal, sends
a signal to the PCM when cruise is engaged. The cruise control module, cruise
cancel signal terminal, is a circuit used by the PCM to inhibit cruise control
when conditions inconsistent with cruise operation are present.
The PCM will inhibit cruise control:
| • | When vehicle speed is less than 40 km/h (25 mph). |
| • | When PARK,REVERSE, NEUTRAL, or 1st gear is indicated by
the transaxle range switch. |
| • | With high engine RPM (fuel cut-off) |
| • | When vehicle speed is to high |
| • | When an over or under charged battery voltage condition exists |
| • | Antilock brake system/traction control system is active for more
than 2 seconds |
| • | A 6 MPH or more decrease in non-drive wheel speed in 0.4 seconds
with out seeing the extended brake travel contacts of the TCC/Brake switch
transition. |
If the PCM determines that any of the cruise control inhibit conditions
are present, the PCM requests that the cruise control module disengage cruise
control. The PCM accomplishes this request by opening the cruise control
cancel signal circuit. If the cruise indicator control signal, sent by the
cruise control module to the PCM, indicates that the cruise control is still
engaged after the PCM has requested that the cruise control disengage, the
PCM sets a DTC.
