Cruise Control: Description and Operation

CRUISE CONTROL DESCRIPTION AND OPERATION

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, 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. 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 steering wheel. The cruise control functional control switches include the ON/OFF, SET/COAST, R/A (resume/accelerate). The switches provide driver control of the cruise control system.

The cruise control release switch, cancel switch and stoplamp 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 cruise control cancel switch is located on the steering wheel. To disengage the system the driver presses the brake pedal or presses the cancel switch. The speed of the vehicle at brake actuation will be stored in the memory of the cruise module.

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 or ignition switch, the cruise control turns off. The vehicle speed stored in the memory of the cruise module will be lost.

Ignition 1 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 1 voltage is applied to the cruise control on switch signal circuit of the cruise control module. If the driver has not pressed the brake pedal or cancel switch, ignition 1 voltage is supplied through the TCC/Brake (cruise release) and cruise control cancel switches, to the cruise release signal circuit 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 circuit of the cruise control module. When the SET/COAST button is pressed , ignition positive voltage is applied to the cruise control set/coast switch signal circuit of the cruise control module. When pressing the R/A (resume/accelerate), ignition positive voltage is applied to the cruise control resume/ accelerate switch signal circuit 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 engaged circuit, sends a signal to the PCM when cruise is engaged. The cruise control module, cruise inhibit signal circuit, is a circuit used by the PCM to disengage cruise control when conditions inconsistent with cruise operation are present.

After the cruise control engaged criteria has been met and the cruise ON and Set/Coast have been commanded, the cruise control module sends a signal to the PCM that the cruise control is engaged.The PCM then sends a class 2 message to the instrument panel cluster (IPC) to illuminate the cruise light.

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.
- With low engine RPM
- 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 will disengage the cruise control. The PCM accomplishes this by opening the cruise control inhibit signal circuit.