Grand Prix V6-3.8L (2007)
Cruise Control: Description and Operation
Cruise Control Description and Operation (3.8L)
Cruise control is a speed control system that maintains a desired vehicle speed under normal driving conditions at speeds above 40 km/h (25 mph).
Steep grades may cause variations in the selected vehicle speeds.
The following are the main components of the cruise control system:
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The accelerator pedal
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The brake pedal position sensor
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The body control module (BCM)
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The driver information center (DIC)
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The instrument panel cluster (IPC)
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The ON/OFF switch
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The powertrain control module (PCM)
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The RES/+ switch
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The SET/- switch
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The throttle actuator control (TAC) module
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The TAC motor
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The vehicle speed sensor
Cruise Control Engaged
The cruise control system will engage and adjust vehicle speeds, based on the activation of the following cruise control switches:
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The ON/OFF switch
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The RES/+ switch
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The SET/- switch
The powertrain control module (PCM) monitors the signal circuit of the cruise control switches. The PCM uses the cruise control set/coast and
resume/accelerate switch signal circuit in order to determine when to capture and maintain the selected vehicle speed. The PCM uses the throttle actuator
control (TAC) module and the TAC motor in order to maintain the vehicle speed. For further review of the TAC system, refer to Throttle Actuator
Control (TAC) System Description for the 3.8L (L26 and L32) engine.
Ignition voltage is supplied to the cruise control switch from the 2-ampere CRUISE SW fuse located in the IP fuse block. The cruise control function
switches are arranged in a resistive ladder design, with each cruise control function switch having a different resistance value. The PCM detects a
specific voltage value that is associated with the cruise control function switch being activated. When the normally open cruise control ON/OFF switch is
turned ON, the switch closes and the PCM detects a predetermined voltage signal on the cruise control cruise control set/coast and resume/accel switch
signal circuit indicating that the ON/OFF switch is active. When the RES/+ switch or the SET/- switch are activated, the PCM detects the predetermined
voltage signal on the cruise control set/coast and resume/accel switch signal circuit. To engage the cruise control system, turn the cruise control system
ON by pressing the cruise ON/OFF button and momentarily activating the SET/- switch. The PCM will engage the cruise control system and the TAC
module will record the vehicle speed. The PCM sends a class 2 message to the DIC in order to activate the CRUISE SET message. The PCM also sends
a class 2 message to the instrument panel cluster (IPC) in order to illuminate the Cruise indicator. The SET/- switch or the RES/+ switch will remain
inactive when the PCM has not received the predetermined voltage signal from the ON/OFF switch. Pressing the accelerator pedal, while the cruise
control system is engaged, will allow the driver to override the cruise control system in order to accelerate the vehicle beyond the current set vehicle
speed. When the accelerator pedal is released, the vehicle will decelerate and resume the current set vehicle speed. The driver can also override the
current set vehicle speed via the SET/- switch and the RES/+ switch. When the cruise control system is engaged, activating and holding the SET/- switch
will allow the vehicle to decelerate from the current set vehicle speed without deactivating the cruise control system. When the SET/- switch is released,
the vehicle will maintain the current vehicle speed as the new set vehicle speed. When the cruise control system is engaged, momentarily activating the
SET/- switch will allow the vehicle to decelerate at 1.6 km/h (1 mph) increments for each time that the SET/- switch is activated, with the minimum
vehicle speed being 37 km/h (23 mph). Activating and holding the RES/+ switch, when the cruise control system is engaged, will allow the vehicle to
accelerate to a greater vehicle speed than the current set vehicle speed. When the RES/+ switch is released, the vehicle will maintain the current vehicle
speed. When the cruise control system is engaged, momentarily activating the RES/+ switch will allow the vehicle to accelerate at 1.6 km/h (1 mph)
increments for each time that the RES/+ switch is pressed, with a maximum acceleration of 16 km/h (10 mph) over the current set vehicle speed.
Momentarily activating the RES/+ switch will recall the previous vehicle speed, after the cruise control system is disengaged by pressing the brake pedal.
Cruise Control Disengaged
The powertrain control module (PCM) disengages the cruise control operation based on the signals from one of the following:
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The brake pedal position (BPP) sensor
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The ON/OFF switch
The BPP sensor is mounted on the brake pedal bracket. Pressing the brake pedal while the cruise control is engaged will disengage the cruise control