Cruise Control: Description and Operation
General DescriptionThe cruise control system maintains a desired vehicle speed under normal driving conditions. The system also has the capability to coast, resume speed, accelerate, and increase or decrease speed in 1.6 kph (1 mph) increments.
The main components of the system are the multi-function switch, cruise control module, vehicle speed sensor (VSS), VSS calibrator, release switches, and electrical harness.
The cruise control module contains an electronic controller and an electric stepper motor. The controller monitors vehicle speed and operates the electric stepper motor. The motor moves a ribbon, which is connected by a cable to the throttle, in response to the controller in order to maintain the desired cruise speed.
The cruise control module contains a low speed lock-out that prevents system engagement below a minimum speed of approximately 40 kph (25 mph).
The controller operates in response to the control switches located on the multifunction switch.
Release switches are used to disengage the cruise control. When either the brake or clutch pedal is depressed, the cruise control system is electrically disengaged, and the throttle returns to the idle position.
CAUTION: To keep the vehicle under control and to prevent possible vehicle damage, do not use the cruise control on slippery roads. It Is not recommended to use the cruise control In conditions such as on winding roads or In traffic of varying volume. When traveling down a steeply graded hill, the cruise control should be disengaged by depressing the brake or clutch pedal lightly. The transmission can then be shifted to a lower gear range to help control vehicle speed.
Cruise Control Module
The cruise control module mounts to the cowl panel. The module has an electronic controller and an electric stepper motor to vary the throttle with each mode. The module is not serviceable.
Release Switches
Either one or two electrical release switches is employed in the cruise control system. One of the switches mounts to the brake pedal, and also functions as the stop lamp switch. On vehicles equipped with manual transmissions, a second switch is used in addition to the brake switch. The switch is mounted to the clutch master cylinder push rod, and also functions as the clutch start switch. When either the brake or clutch pedal is depressed, the release switch cuts off the voltage supplied to the cruise control circuit in the PCM/VCM. The engagement switch must be energized to return the cruise control to operation.
Vehicle Speed Sensor
The Vehicle Speed Sensor (VSS) mounts to the automatic or manual transmission assembly and uses a permanent magnet generator to produce an Alternating Current (AC) signal. The frequency of this signal is proportional to the speed at which the transmission output shaft rotates, which in turn is proportional to the speed of the vehicle.
The AC signal produced by the VSS is amplified and converted by the VSS calibrator. The signal is supplied to the PCM/VCM,
cruise control module, and speedometer by the VSS calibrator. The VSS calibrator produces the signal by opening and closing internal solid-state switches to ground. The VSS calibrator is integral to the PCM/VCM and is not serviceable.
The signal to the PCM/VCM, cruise control module, and speedometer pulses at a rate of 4,000 times per mile. The PCM/VCM, cruise control module, and speedometer internally convert the number of pulses per mile to determine vehicle speed.
Vehicle Speed Sensor Calibrator
The Vehicle Speed Sensor (VSS) calibrator receives a signal from the VSS indicating the speed of the vehicle. A This signal is then processed by the VSS calibrator and supplied to the Powertrain Control Module (PCM) (2.2 liter engine) or Vehicle Control Module (VCM) (4.3 liter engine), cruise control module, and the speedometer.
Multifunction Switch
OFF-ON-R/A
The OFF-ON-R/A (Resume/Accelerate) slide switch, located on the multifunction switch, controls four functions.
The OFF/ON Function
When the OFF-ON-R/A switch is in the OFF position the system cannot be engaged. When the switch is in the ON position, the system may be engaged at any speed above approximately 40 kph (25 mph).
The accelerator may be depressed at any time to override the cruise control system. Release of the accelerator will return the vehicle to the previously set cruise speed.
The Resume Function
If the cruise control system has been disengaged by depressing the brake or clutch pedal, it may be reactivated by momentarily sliding the OFF-ON-R/A switch to the R/A position. This will cause the vehicle to accelerate to the previously set speed and cruise at that speed. The resume function will not work if the OFF-ON-R/A switch has been moved to the OFF position, the ignition switch has been cycled since the last time the cruise control was active, or the vehicle speed is below the low speed lockout of 40 kph (25 mph).
The Accelerate Function
By sliding the OFF-ON-R/A switch to the R/A position and holding it, the vehicle will accelerate until the switch is released. The cruise control must be engaged and operating and the vehicle speed must be above the low speed lockout of 40 kph (25 mph) for this function to operate.
The "Tap Up" Function
For this function to operate, the cruise control must be engaged and operating. "Tapping up" is done by sliding the OFF-ON-R/A switch to the R/A position and immediately releasing it, or "tapping" the switch. Do not hold the switch in the R/A position or the system will revert to the accelerate mode. "Tap up" is a function in which cruise speed can be increased by 1.6 kph (1 mph) increments (one tap = 1.6 kph or 1 mph increase). The system cannot "tap up" beyond the vehicle's maximum speed.
SET Switch
The cruise control SET button switch controls three functions.
The Set Function
When the SET switch is depressed and then released, with vehicle speed above the low speed lockout point, and the OFF-ON-R/A switch in the ON position, the cruise speed will be set at the particular speed the vehicle was at when the switch was released. Cruise speed will be within 1.6 kph (1 mph) of the actual speed when engaged. The system will cruise until either the OFF-ON-R/A switch is moved to the OFF position, the ignition switch is turned to the OFF position, and/or the SET switch is depressed and held. Pushing the brake or clutch pedal disengages the system, but the set speed is maintained in memory, allowing the cruise speed to be resumed at a later time.
The Coast Function
When the SET switch is depressed, the vehicle speed can be raised or lowered. To increase cruise speed, accelerate to a new speed, depress the SET switch, so that the PCM/VCM releases the previously set speed, and release the switch. Upon releasing the switch, a new speed is set. An increased cruise speed can also be more easily set with the ON-OFF-R/A switch as described above. To decrease cruise speed, depress the SET switch to disengage the cruise control system, and allow the throttle to return to the idle position. When the vehicle has slowed to the desired lower cruise speed, release the switch to cause the system to cruise at the new speed.
The "Tap Down" Function
For this function to operate, the cruise control must be engaged and operating. "Tapping down" is done by depressing the SET switch and immediately releasing it, or "tapping" the switch. Do not hold the switch in the depressed position or the system will revert to the coast mode. "Tap down" is a function in which cruise speed can be decreased by 1.6 kph (1 mph) increments (one tap = 1.6 kph or 1 mph decrease). The system can "tap down" to the low speed lockout of 40 kph (25 mph). Below this speed, the cruise control will not operate.
Circuit Operation
The Electro-Motor Cruise Control is a speed control system which maintains a desired vehicle speed under normal driving conditions. The system has the capability to CRUISE, COAST, RESUME SPEED, ACCELERATE, TAP-UP and TAP-DOWN.
Depressing the Set and R/A Switches simultaneously will cancel cruise control operation, without removing memory speed.
An Electronic Controller and Electric Motor are contained in the Cruise Control Module. The Controller monitors vehicle speed and operates the Stepper Motor. In response to the Controller, the motor moves a connecting strap that is attached to the Cruise Control Cable. The Cruise Control Cable moves the Throttle Linkage to vary throttle position in order to maintain the desired speed. The Cruise Control Module prevents system engagement below a minimum speed of approximately 25 mph. The module is controlled by mode control switches which are part of the multifunction lever.
With the Ignition Switch in RUN battery voltage is applied to the Cruise Control Module through the BRN (441) wire. When the Cruise Control Switch is moved to the ON position, battery voltage is applied to the Cruise Control Module through the GRY (397) wire. If the brake pedal or clutch is not depressed, battery voltage is present at the module through the BRN/WHT (379) wire for manual transmission vehicles or the PPL (420) wire for automatic transmission vehicles. When the brake pedal is pressed, battery voltage is applied to the Cruise Control Module through the WHT (17) wire and removed from the PPL (420) wire. When the Clutch Pedal is pressed, battery voltage is removed from the BRN/WHT (379) wire When the Cruise Control Switch is moved to the RIA position, battery voltage is applied to the module via the GRY/BLK wire. With the Set/Coast Switch depressed, battery voltage is present at the module through the DK BLU (84) wire.The Cruise Control Module receives vehicle speed signal inputs through the BRN (818) wire if the vehicle is equipped with a 2.2L engine or the DK GRN/WHT (817) wire for a 4.3L engine. In operation, voltage will oscillate between a high of 4 to 5 volts and a low of near 0 volts. Ground for the Cruise Control Module is provided through the BLK/WHT (151) wire.