Cruise Control Servo Assembly: Notes

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:

Fig 1: Main Cruise Control Switch - CRUISE On/OFF Positions

Courtesy of GENERAL MOTORS CORP.

• The main cruise control switch - CRUISE On/OFF.
  Fig 2: Cruise Control Mode Switch - RESUME/ACCEL, COAST/SET & CANCEL

  Courtesy of GENERAL MOTORS CORP.
• 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 main cruise control switch - CRUISE ON/OFF
• The ON/OFF input
• The speed control input
• The throttle position
• The cancel input

Fig 3: Main Cruise Control Switch - CRUISE ON/OFF Positions

Courtesy of GENERAL MOTORS CORP.

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

Fig 4: Cruise Control Mode Switch

Courtesy of GENERAL MOTORS CORP.

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:

Fig 5: Cruise Control Switch CANCEL Button

Courtesy of GENERAL MOTORS CORP.

• 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.