Cruise control is a speed control system that maintains a desired vehicle speed
under normal driving conditions. However, steep grades may cause variations in the
selected speeds. The electronic cruise control system has the capability to CRUISE,
COAST, RESUME SPEED, ACCELERATE, TAP-UP or TAP-DOWN.
The main parts of the cruise control system are:
| • | The powertrain control module (PCM) |
| • | The function control switches |
| • | The stop lamp switch assembly |
The cruise control system uses the powertrain control module (PCM) to maintain
the desired vehicle cruise speed . The PCM assembly contains a low speed limit which
will prevent system engagement below a minimum speed of 40 km/h (25 mph).
The PCM assembly is not serviceable.
Cruise control operation is controlled through the function control switches
located on the multifunction turn signal lever. The cruise control function control
switches includes the ON/OFF, SET/COAST, R/A (resume/accelerate). The switch assembly
provides driver control of the cruise control system.
The stop lamp switch is used to disengage the cruise control. A cruise control
release switch circuit and a stop lamp switch circuit are used. The stop lamp switch
is mounted to the brake pedal bracket . To disengage the system the driver presses
the brake pedal. The speed of the vehicle at brake actuation will be stored in the
memory of the PCM.
With cruise control, the vehicle 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 cruise control ON/OFF switch or ignition switch, the cruise control
turns off. The vehicle speed stored in the memory of the PCM will be lost.
Ignition positive voltage is supplied from the HVAC fuse, to the cruise control
switch. When the cruise control ON/OFF switch is on, ignition positive voltage is
applied to the cruise on switch signal circuit terminal of the PCM. If the driver
has not pressed the brake pedal, ignition positive voltage is supplied through the
stop lamp switch, TCC/Brake signal contacts to the cruise control brake pedal switch
signal circuit terminals of the PCM. Cruise control is canceled when the driver presses
the brake pedal. The stop lamp switch contacts close, applying battery positive voltage
to the stop lamp signal circuit of the PCM. At the same time, the TCC/Brake contacts
of the stop lamp switch open and voltage is removed from the brake pedal signal circuit
at the PCM. When pressing the SET/COAST button on the multifunction turn signal lever,
ignition positive voltage is applied to the set/coast switch signal terminal of the
PCM. 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 PCM.
When the cruise switch is in the ON position, and the driver presses the SET/COAST
button, the PCM then checks to see that the cruise control enable criteria is met.
If the cruise control criteria has been met the PCM sends a class 2 message
to the instrument panel cluster (IPC) to illuminate the cruise light.
The PCM will inhibit cruise control:
| • | When the PCM detects that the center high mounted stop lamp (CHMSL) in
not operating properly. |
| • | When vehicle speed is less than 40 km/h (25 mph). |
| • | When in PARK, REVERSE, NEUTRAL, or 1st gear. |
| • | 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 |
If the PCM determines that any of the cruise control inhibit conditions are
present, the PCM will disengage the cruise control. If the PCM disables the cruise
control for an inhibiting event it will record the reason for disengagement in the
Disengage Definition data file.
