TrailBlazer 4WD L6-4.2L (2007)
Cruise Control: Description and Operation
Cruise Control Description and Operation (4.2L)
Cruise control is a speed control system that maintains a desired vehicle speed under normal driving conditions at vehicle 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 powertrain control module (PCM)
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The On/Off switch
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The Resume/Accel switch
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The Set/Coast switch
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The torque converter clutch (TCC) brake switch
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The stop lamp switch
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The throttle actuator control (TAC) motor
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The vehicle speed sensor (VSS)
Cruise Control Engaged
The cruise control system will engage and adjust the vehicle speed based on the activation of the following cruise control switches:
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On/Off
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Resume/Accel
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Set/Coast
The cruise control switches are located on the multifunction/turn signal lever.
The powertrain control module (PCM) monitors the signal circuits of the cruise control switches in order to determine when to capture and maintain the
selected vehicle speed. The PCM uses the throttle actuator control (TAC) module motor in order to control the vehicle speed. For further information on
the TAC system, refer to Throttle Actuator Control (TAC) System Description.
Ignition positive voltage is supplied from the 10-amp HVAC 1 fuse to the cruise control switch via the ignition 3 voltage circuit. When the normally
open cruise control On/Off switch is turned ON, the switch closes and the PCM detects a high signal voltage on the cruise control on switch signal
circuit. When the normally open Set/Coast switch is pressed, the switch closes and the PCM detects a high signal voltage on the cruise control set/coast
switch signal circuit. To engage the cruise control system, turn the On/Off switch ON and momentarily press the Set/Coast switch. The PCM will
confirm that the cruise control enable criteria has been achieved. The PCM will engage the cruise control system and record the selected vehicle speed.
The PCM sends a class 2 message to the instrument panel cluster (IPC) in order to illuminate the cruise control indicator. 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/Coast switch and the Resume/Accel switch. When the cruise control system is engaged, pressing and
holding the Set/Coast switch will allow the vehicle to decelerate from the current set vehicle speed without deactivating the cruise control system. When
the Set/Coast switch is released, the PCM will record the vehicle speed and maintain the vehicle speed as the new set vehicle speed. When the cruise
control system is engaged, momentarily pressing the Set/Coast switch will allow the vehicle to decelerate at 1 mph increments for each time that the
Set/Coast is momentarily pressed, with a minimum vehicle speed of 23 mph. When the normally open Resume/Accel switch is activated, the switch
closes and the PCM detects a high signal voltage on the cruise control resume/accel switch signal circuit. Activating and holding the Resume/Accel
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 Resume/Accel switch is released, the PCM will record the vehicle speed and maintain the vehicle speed as the new set vehicle speed. When the
cruise control system is engaged, momentarily activating the Resume/Accel switch will allow the vehicle to accelerate at 1 mph increments for each time
that the Resume/Accel switch is momentarily activated, with the maximum acceleration total of 10 mph over the current set vehicle speed. Momentarily
activating the Resume/Accel switch, after the cruise control system has been disengaged by pressing the brake pedal, will recall the previous set vehicle
speed that is recorded in the PCM.
Cruise Control Disengaged
The powertrain control module (PCM) disengages the cruise control operation based on the signals from the following switches:
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The On/Off switch
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The torque converter clutch (TCC) brake switch
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The stop lamp switch
The TCC brake switch and the stop lamp switch are incorporated into an assembly and are mounted to the brake pedal bracket. Pressing the brake pedal
while the cruise control is engaged will disengaged the cruise control system. The PCM monitors the TCC brake switch/cruise control release signal
circuit and the stop lamp switch signal circuit. When the brake pedal is pressed, the normally closed TCC brake switch opens and the normally open stop
lamp switch closes. The PCM detects a low signal voltage on the TCC brake switch/cruise control release signal circuit and detects a high signal voltage