GM Service Manual Online
For 1990-2009 cars only

Caution: Do not use the cruise control on slippery roads, steeply graded roads, or in heavy traffic of heavy or varying volume. Failure to follow these CAUTIONS could possibly cause you to loose control of the vehicle and result in damage to the vehicle and personal injury.

Cruise control is a speed control system that maintains a desired vehicle speed under normal driving conditions. The cruise control allows the driver to maintain a constant speed of 40 km/h (25 mph) or higher without depressing the accelerator. Any steep grades up or down may cause variations in the selected speeds. The cruise control system performs the following functions:

    • Cruising
    • Coasting
    • Resuming Speed
    • Accelerating

The cruise control system consists mainly of the following components:


Object Number: 488527  Size: MH
    • The cruise control servo assembly (6)
    • The cruise control release and clutch pedal position (CPP) switch, manual transmission only

Object Number: 488520  Size: MH
    • The cruise control mode switch - RESUME/ ACCEL, COAST/ SET, and CANCEL (1)

Object Number: 812034  Size: SH
    • The main cruise control switch - CRUISE ON/OFF
    • The powertrain control module (PCM)
    • The transmission range switch, automatic transmission only
    • The stoplamp switch
    • The vehicle speed sensor (VSS)

The cruise control servo assembly allows the system to control and maintain the desired vehicle speed. The functions of the cruise control system are received and acted upon by the cruise control module. The cruise control module is incorporated into the cruise control servo assembly. The cruise control module sends a command through the cruise control servo to engage the system when the module receives one of the following signals from the cruise control mode switch:

    • Cruise
    • Coast
    • Resume
    • Accelerate

When a command is received by the servo, the direct current (DC) servo turns a worm gear. The turning of the worm gear moves the accelerator cable in order to adjust the throttle angle. The DC servo and the worm gear connect mechanically only when a magnetic clutch, situated between the DC servo and the worm gear, energizes.

The system is disengaged when the cruise control module sends a command to the cruise control servo. The cruise control module receives a cancel signal from any of the following components:

    • The stop lamp switch

Object Number: 812034  Size: SH
    • The main cruise control switch - CRUISE ON/OFF

Object Number: 488520  Size: MH
    • The cruise control mode switch - RESUME/ ACCEL, COAST/ SET, and CANCEL (1)
    • The transmission range switch, automatic transmission only
    • The clutch pedal position (CPP) switch, manual transmission only

Upon receiving a cancel signal, the cruise control servo assembly de-energizes the magnetic clutch. When the magnetic clutch de-energizes, the DC servo motor and the worm gear mechanically disconnect. The throttle returns to the idle position.

Cruise Control Servo Assembly

The cruise control servo assembly is mounted to the left inner wheelhouse panel in the engine compartment. The cruise control servo assembly consists of the following components:

    • The DC servo
    • The worm gear
    • The magnetic clutch
    • The cruise control module

The cruise control servo actuates the accelerator cable in order to increase and decrease the throttle angle in response to signals from the following locations:


Object Number: 812034  Size: SH
    • The main cruise control switch - CRUISE ON/OFF

Object Number: 488520  Size: MH
    • The cruise control mode switch - RESUME/ ACCEL, COAST/ SET, and CANCEL (1)
    • The vehicle speed sensor (VSS) - speedometer

The input signals received by the cruise control servo assembly are broken down into the following categories:

    • The ON/OFF input
    • The speed control input
    • The throttle position
    • The cancel input

Object Number: 812034  Size: SH

The main cruise control switch - CRUISE ON/O5FF provides the ON/OFF signal to the cruise control servo assembly in order to activate and deactivate the cruise control system.


Object Number: 488520  Size: MH

The cruise control mode switch (1) provides the following speed control input signals:

    • The RESUME/ACCEL - resume/accelerate
    • The COAST/SET

The cruise control servo assembly uses the speed control input signals and the vehicle speed signal from the VSS in order to determine, maintain, or alter the vehicle speed. The vehicle speed depends on the driver commands.

The powertrain control module (PCM) provides the throttle position signals to the cruise control servo assembly through of the throttle position (TP) sensor. The throttle position signals allow the cruise control servo assembly to constantly monitor the throttle position during the operation of the cruise control system.

The cancel input signals are provided to the cruise control assembly by the following components:


Object Number: 488520  Size: MH
    • The cruise control switch CANCEL button (2)
    • The stop lamp switch
    • The transmission range switch - automatic transmission only
    • The clutch pedal position (CPP) switch - manual transmission only

The cancel input signals inform the cruise control servo assembly to immediately suspend the cruise control operation.

An output signal is sent to the open side of the DC servo motor when the cruise control servo assembly senses a drop in the vehicle speed below the desired cruise speed. The output signal causes the DC servo motor to perform the following actions:

    • Turn the worm gear
    • Open the throttle
    • Increase the vehicle speed to the desired cruise speed

An output signal is sent to the closed side of the DC servo motor when the cruise control actuator assembly senses that the vehicle speed is above the desired cruise speed. The output signal causes the DC servo motor to perform the following actions:

    • Turn the opposite direction
    • Close the throttle
    • Decrease the vehicle speed to the desired cruise speed

The cruise control servo assembly de-energizes the magnetic clutch when a cancel input signal is received. The cancel signal disengages the DC servo motor from the worm gear. Disengaging the DC servo motor causes the throttle to go to the idle position. The cruise control operation cancels when the throttle is in the idle position.

Vehicle Speed Sensor (VSS)

The vehicle speed sensor (VSS) is mounted on either the transfer case or transmission. The VSS converts the vehicle speed into a pulse signal. The pulse signal sends the input to the cruise control servo assembly.

Cruise Control Release and Clutch Pedal Position (CPP) Switch - Manual Transmission

The cruise control release and clutch pedal position (CPP) switch mounts under the instrument panel, directly above the clutch pedal. The CPP switch closes, providing a ground to the cruise control servo assembly, whenever you press the clutch pedal. The cruise control servo assembly disengages the cruise control system operation as soon as the ground signal is sensed.

Transmission Range Switch - Automatic Transmission

The transmission range switch mounts to the transmission. The transmission range switch closes, providing a ground to the cruise control servo assembly, when the manual lever is in the PARK or the NEUTRAL position. The cruise control servo assembly disengages the cruise control system operation as soon as the ground signal is sensed.

Stop Lamp Switch

The stop lamp switch is under the instrument panel, directly above the brake pedal. When you press the brake pedal, 1 set of the stop lamp switch contacts close. The closed contacts provide a voltage signal to the cruise control servo assembly. The cruise control servo assembly disengages the cruise control operation as soon as the voltage signal is sensed.

When you press the brake pedal, another set of stop lamp switch contacts open. The open contacts interrupts the voltage circuit from the cruise control servo assembly to the magnetic clutch, inside the assembly. With the voltage removed from the magnetic clutch, the actuator DC servo disengages from the worm gear. This action permits the throttle to return to the idle position. This ensures the cancellation of the cruise control operation during vehicle braking.

Throttle Position (TP) Sensor

The throttle position (TP) sensor supplies a throttle position voltage signal input to the powertrain control module (PCM). The PCM converts the TP sensor signal into a throttle duty signal. The duty signal is relative to the rate at which the throttle plate is opening. The cruise control actuator assembly uses the information in order to determine the throttle opening angle.

Cruise Indicator


Object Number: 488517  Size: MH

The cruise indicator is in the upper center portion of the instrument cluster (1). The cruise indicator lights in order to inform the driver that the cruise control system is operational.

Main Cruise Control Switch (CRUISE ON/OFF)


Object Number: 812034  Size: SH

The main cruise control switch - CRUISE ON/OFF has 2 momentary contact buttons. The main cruise control switch is on the instrument panel, to the right of the steering column. The switch turns the cruise control system ON or OFF. Once the main cruise switch is turned ON, it will be operational whenever the ignition switch is turned on.

RESUME/ACCEL Switch


Object Number: 488520  Size: MH

The RESUME/ ACCEL - Resume/ Accelerate switch (1) is a part of the cruise control mode switch. The RESUME/ ACCEL switch returns the cruise control system operation to the last speed setting after a cancel input signal is received by the cruise control servo assembly, such as vehicle braking.

The RESUME/ ACCEL switch activates when the cruise control switch momentarily rotates clockwise. Do not hold the cruise control switch in the RESUME/ACCEL position. If you hold the cruise control switch in the RESUME/ACCEL position for more the 1 second, the system will go into the accelerate mode.

Rotate and hold the cruise control switch in the RESUME/ ACCEL position in order to accelerate during the cruise control system operation. When the cruise control switch releases, the cruise control system will maintain the new cruise speed.

In order to use the accelerate mode, the following conditions must be present:

    • You must press the main cruise control switch - CRUISE ON/OFF.
    • The CRUISE indicator must be lit.
    • The vehicle speed must be over 25 mph (40 km/h).

COAST/ SET Switch


Object Number: 488520  Size: MH

The COAST/SET switch is part of the cruise control mode switch (1). The COAST/SET switch activates when the cruise control switch rotates counterclockwise into the COAST/SET position.

When you rotate the cruise control switch to the COAST/SET position and release the switch the vehicle will travel at the previously set speed. The following conditions must be present in order for the COAST/SET switch to operate:

    • You must press the main cruise control switch - CRUISE ON/OFF.
    • The CRUISE ON/OFF indicator must be lit.
    • The vehicle speed must be over 40 km/h (25 mph).

The COAST/ SET switch may be used in order to decease the cruise speed. Rotate the cruise control switch counterclockwise to the COAST/ SET position. Hold the cruise control switch in order to disengage the cruise control system and return the throttle to the idle position. When the new, lower cruise speed is reached, the cruise control switch will release from the COAST/ SET position. The cruise control system will re-engage and maintain the new cruise speed.

You may press the accelerator at any time in order to override the cruise control system operation. Release the accelerator in order to return the vehicle to the previously set cruise speed.

CANCEL BUTTON


Object Number: 488520  Size: MH

The CANCEL button (2) is part of the cruise control mode switch (1). When you press the CANCEL button, the button signals the cruise control servo assembly in order to immediately suspended cruise control operation.

When the ignition is turned to the ON position, battery voltage is applied to cavity 12 of the cruise control servo through the closed contacts of the main relay. Ground for the cruise control servo is applied at cavity 11. Depressing and releasing the main cruise control switch closes the momentary switch contacts and signals the cruise control servo at cavity 8 to turn ON. The cruise control servo then grounds cavity 10 to turn ON the cruise control switch indicator lamp. The vehicle speed sensor (VSS) signal is applied at cavity 1 of the cruise control servo and allows it to monitor vehicle speed.

Operating the cruise control mode switch applies the following resistances between cavities 5  and 8 of the cruise control servo:

    • CANCEL -- 0 ohms
    • RES/ACC -- 910 ohms
    • SET/COAST -- 230 ohms

Whenever the cruise control system is in operation, ground from cavity 4 of the cruise control servo is applied to the CRUISE indicator in the Instrument Cluster.

When the brake pedal is depressed, one set of the stop lamp switch contacts close and applies B+ voltage to the brake lights and to cavity 2 of the cruise control servo which cancels the cruise control operation. The other set of stop lamp switch contacts open and removes B+ voltage from cavity 6 of the cruise control servo which removes voltage to the magnetic clutch in the cruise control servo.

Cruise control operation is also canceled when ground is applied at cavity 9 of the cruise control servo during the following conditions:

    • Clutch pedal depressed - Manual Transaxle.
    • Manual selector placed in the P or N position - Automatic Transaxle.

The Powertrain Control Module (PCM) provides a throttle position sensor signal to cavity 7 of the cruise control servo. This signal is used by the cruise control servo as one of the factors in determining when to provide an overdrive cutoff signal to the PCM.

When certain driving conditions exist which require the vehicle to shift out of overdrive, the cruise control servo sends an overdrive cutoff signal from cavity 3 to the PCM.