Envoy 4WD V8-5.3L VIN M (2005)
Cruise Control: Description and Operation
CRUISE CONTROL DESCRIPTION AND OPERATION (5.3L)
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 engine control module (ECM)
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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/cruise release 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 engine control module (ECM) monitors the signal circuits of the cruise control switches in order to determine when to capture and maintain the
selected vehicle speed. The ECM uses the throttle actuator control (TAC) motor in order to control the vehicle speed. For further information on the
TAC system, refer to Throttle Actuator Control (TAC) System Description in Computers and Control Systems - 5.3L.
Ignition positive voltage is supplied from the 10-amp CRUISE 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 ECM 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 ECM 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 ECM will
confirm that the cruise control enable criteria has been achieved. The ECM will engage the cruise control system and record the selected vehicle
speed. The ECM sends a class 2 message to the instrument panel cluster (IPC) in order to illuminate the Cruise 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 ECM will record 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 1.6 km/h (1 mph) increments for each time
that the set/coast is momentarily pressed, with a minimum vehicle speed of 37 km/h (23 mph). When the normally open resume/accel switch is
activated, the switch closes and the ECM 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 ECM will record 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 1.6 km/h (1 mph) increments
for each time that the resume/accel switch is momentarily activated, with the maximum acceleration total of 16 km/h (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 ECM.
Cruise Control Disengaged
The engine control module (ECM) 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/cruise release switch
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The stop lamp switch
The TCC brake/cruise release 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 ECM 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 ECM detects a low signal voltage on the TCC brake switch/cruise control release signal circuit and
detects a high signal voltage on the stop lamp switch signal circuit. The cruise control system will disengage when the cruise control on/off switch is
turned OFF. When the cruise control system is disengaged, the ECM sends a class 2 message to the instrument panel cluster (IPC) in order to
deactivate the Cruise indicator. The vehicle speed stored in the memory of the ECM will be erased when the cruise control on/off switch is turned to
OFF, or the ignition switch is turned OFF.
The cruise control system will disengage when the ECM detects that the accelerator pedal override is active for greater than 60 seconds.