Cruise Control System
Gasoline Engines
The cruise control system on gasoline engines consists of the following
components:
| • | The vehicle control module (VCM) |
| • | The cruise control module |
| • | The multifunction lever |
| • | The brake release switch |
The cruise control module contains a stepper motor that is used to change
throttle position. The cruise control module receives commands from the multifunction
lever. The cruise control module receives vehicle speed from the VCM.
The cruise control module controls speed based on these input commands
and the vehicle speed.
Diesel Engines
The cruise control system on the diesel engines consists of the following
components:
| • | The powertrain control module (PCM) |
| • | The electronic throttle control system |
| • | The vehicle speed sensor buffer (VSSB) |
| • | The multifunction lever |
| • | The brake release switch |
The PCM receives commands from the multifunction lever. The PCM also
receives vehicle speed information from the VSSB. The PCM sends information
to the electronic throttle control system in order to control vehicle
speed based on these input commands and vehicle speed.
Brake Release Switch
Gasoline Engines
The cruise control module uses an electronic brake switch that contains
one normally open and one normally closed switch contact. These switch contacts
are part of the zero adjust brake switch.
When the brake pedal is depressed, the two brake switch contacts change
their input state at the cruise control module. The cruise control module
then shuts off all cruise control outputs.
Diesel Engines
The powertrain control module (PCM) uses an electronic brake switch
that contains one normally open and one normally closed switch contact. These
switch contacts are part of the zero adjust brake switch.
When the brake pedal is depressed, the two brake switch contacts change
their input state at the PCM. The PCM then shuts off all cruise control outputs
to the electronic throttle system.
Vehicle Speed Signal
Gasoline Engines
The vehicle speed sensor (VSS) at the transmission generates the vehicle
speed signal. This signal is then translated by the vehicle control module
(VCM).
The VSS mounts to the automatic transmission assembly and produces an
AC signal. The frequency of this signal equals the transmission output shaft
speed.
The AC signal is sent to the VCM to be amplified and converted to a
digital square wave that represents the vehicle speed in terms of pulses per
mile. The VCM provides a 4,000 pulses per mile signal to the cruise
control module and the speedometer in the instrument cluster.
Diesel Engines
The vehicle speed sensor (VSS) at the transmission generates the vehicle
speed signal. This signal is then translated by the VSS buffer.
The VSS mounts to the automatic transmission assembly and produces an
AC signal. The frequency of this signal equals the transmission output shaft
speed.
The AC signal is sent to the VSS buffer to be amplified and converted
to a digital square wave that represents the vehicle speed in terms of pulses
per mile. The VSS buffer provides a 4,000 pulses per mile signal.
This 4,000 pulses per mile signal is provided to the powertrain
control module (PCM) and the speedometer in the instrument cluster.
Cruise Control Module
Gasoline Engines
The cruise control module on gasoline engines maintains a desired vehicle
speed under normal driving conditions. The typical cruise control system operates
in the following way:
| • | The cruise ON/OFF switch must be in the ON position. |
| • | When the SET button is activated, the cruise control module stores
the last vehicle speed input from the VCM into memory. |
| • | The stepper motor, part of the cruise control module, increases
or decreases throttle position depending on the load (going up or down a hill)
in order to maintain vehicle speed. |
| • | When the cruise ON/OFF switch is moved to the OFF position, or
if the brake is applied, the cruise control module turns off the cruise control
system. |
Diesel Engines
The powertrain control module (PCM) on diesel engines takes the place
of the cruise control module. The typical cruise control system operates in
the following way:
| • | The cruise ON/OFF switch must be in the ON position. |
| • | When the SET button is activated, the PCM stores the last vehicle
speed input from the VSS buffer into memory. |
| • | The PCM then sends signals to the electronic throttle control
system. |
| • | The PCM controls the electronic throttle in order to maintain
the vehicle speed stored in the memory. |
| • | The electronic throttle is a servo system that sends position
information to the PCM. |
| • | The PCM will increase or decrease throttle position depending
on the load (going up or down a hill) in order to maintain vehicle speed. |
| • | When the cruise ON/OFF switch is moved to the OFF position, or
if the brake is applied, the PCM turns off the cruise control system. |
Multifunction Lever
ON/OFF Switch
The ON and OFF position slide switch, on the multifunction lever assembly,
controls electrical power to the cruise control system. When the switch is
OFF, you cannot engage the system. When the switch is ON, you can engage
the system by the SET or RESUME switch at any speed above approximately
40 km/h (25 mph).
SET/COAST Button
The SET/COAST button controls the following 3 functions:
- The SET Function
When the SET/COAST button is pressed and then released, with vehicle
speed above the low speed limit point, and the ON/OFF switch in the ON position,
the cruise speed sets at the particular speed the vehicle was at when
the button was released. Cruise speed will be within 1.6 km/h
(1 mph) of actual vehicle speed when engaged.
The system will cruise until you do any of the following functions:
| • | Move the ON/OFF switch to the OFF position. |
| • | Turn the ignition switch to the OFF position. |
| • | Push in the SET/COAST button and hold. |
| • | This disengages the system, but the set speed is stored in memory allowing
a RESUME at a later time. |
- The COAST (TRIM) Function
When the SET/COAST button is fully pressed, the driver can raise or
lower the control speed. In order to increase control speed, accelerate to
a new speed and fully press the button. The VCM releases the previously
set speed. Then, release the button. When the button is released, this
sets a new speed.
You can also more easily set an increased control speed using the RESUME/ACCEL
switch. Refer to the description of the RESUME/ACCEL R/A Switch in this section.
In order to decrease cruise speed, hold in the SET/COAST button in order
to disengage the cruise system. This allows the throttle to return to the
idle position. When the vehicle slows to the desired lower cruise speed,
releasing the button causes the system to cruise at the new speed.
- The TAP DOWN Function
In order to make this function operate, the cruise must be engaged and
operating. Tapping down means quickly pressing the SET/COAST button and quickly
releasing the SET/COAST button or" tapping" the button. If
you hold in the button, the system reverts to a "coast" mode.
With the tap down function, cruise speed can be decreased by 1.6 km/h
(1 mph) increments. One tap equals a 1.6 km/h (1 mph)
decrease. The system can tap down to the engage speed lockout of 40 km/h
(25 mph). Below this speed, the cruise control will not operate.
You can press the accelerator at any time to override the cruise system.
Releasing the accelerator allows the vehicle to return to the previously set
cruise speed.
RESUME/ACCEL (R/A) Switch
The RESUME/ACCEL switch controls the following 3 functions:
The RESUME Function
| • | If the cruise system has been disengaged by pressing the brake
pedal, you can reactivate the system by momentarily holding the RESUME/ACCEL
switch. The vehicle will accelerate to the previously set speed. The
vehicle will cruise at that speed. |
| • | The RESUME function will not work under the following conditions: |
| • | The cruise ON/OFF switch, or the ignition switch, has been cycled
since the last time the cruise was active. |
| • | The vehicle speed is below the low speed lockout of 40 km/h
(25 mph). |
The ACCELERATE Function
| • | Sliding the RESUME/ACCEL switch to the right and holding the switch
will make the vehicle accelerate until you release the switch. |
| • | The ACCELERATE function works under the following conditions: |
| • | The cruise ON/OFF switch must be ON. |
| • | The vehicle speed must be above the low speed lockout of 40 km/h
(25 mph). |
The TAP UP Function
| • | Tapping up means pressing the slide switch toward the R/A position
and quickly releasing the switch, or tapping the lever. If you hold the
lever in the R/A position, the system will revert to the ACCEL mode. |
| • | With the TAP UP function, cruise speed can be increased by 1.6 km/h
(1 mph) increments. One tap equals a 1.6 km/h (1 mph)
increase. The system cannot tap up beyond 201 km/h (125 mph). |
| • | In order to operate this function, the cruise must be engaged
and operating. |
