Cruise Control Description and Operation With Throttle Actuator Control
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:
• | The powertrain control module (PCM) |
• | The Resume/Accel switch |
• | The torque converter clutch (TCC)/brake switch |
• | The throttle actuator control (TAC) module |
• | The vehicle speed sensor (VSS) |
Cruise Control Engaged
The throttle actuator control (TAC) module monitors the signal circuits of the
following cruise control switches:
The powertrain control module (PCM) will engage and adjust vehicle speed based
on the information received from the TAC module via the universal asynchronous receiver
transmitter (UART) serial data link. For further information on the TAC system, refer
to
Throttle Actuator Control (TAC) System Description
in Engine Controls - 4.8L, 5.3L, and 6.0L.
The cruise control switches are located on the multifunction/turn signal lever.
Ignition positive voltage is supplied from the 10-amp IGN E fuse to the
cruise control switch via the ignition 1 voltage circuit. When the normally
open cruise control On/Off switch is turned ON, the switch closes and the TAC module
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 TAC module
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 TAC module sends a UART message to the PCM, in order to
confirm that the cruise control enable criteria has been met. 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 1.6 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 TAC module 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 1.6 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 PCM.
Cruise Control Disengaged
The powertrain control module (PCM) disengages the cruise control operation
based on the information received from the throttle actuator control (TAC) module.
The TAC module and the PCM monitor the signal circuits of the following switches:
• | The torque converter clutch (TCC)/brake 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 TAC module monitors
the stop lamp switch signal circuit and the PCM monitors the TCC brake switch/cruise
control release signal circuit. When the brake pedal is pressed, the normally closed
TCC brake switch opens and the normally open stop lamp switch closes. The TAC module
detects a high signal voltage on the stop lamp switch signal circuit and the PCM detects
a low signal voltage on the TCC brake switch/cruise control release signal circuit.
The TAC module sends a universal asynchronous receiver transmitter (UART) message
to the PCM indicating the status of the stop lamp switch. The Cruise Control System
will disengage when the cruise control On/Off switch is turned OFF. The vehicle speed
stored in the memory of the PCM 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 PCM detects that the driver
has the accelerator pedal override active for approximately 60 seconds.
When the Cruise Control System is disengaged, the PCM sends a class 2
message to the instrument panel cluster (IPC) in order to deactivate the cruise control
indicator.
Cruise Control Inhibited
The powertrain control module (PCM) inhibits the cruise control operation when
any of the following conditions exist:
• | A Cruise Control System related DTC has been set. |
• | The vehicle speed is less than 40 km/h (25 mph). |
• | The vehicle is in PARK, REVERSE, NEUTRAL, or 1st gear. |
• | The engine RPM is too low. |
• | The engine RPM is too high. |
• | The vehicle speed is too high. |
• | The system voltage is not between 6-16 volts. |
• | The Antilock Brake System (ABS)/Traction Control System (TCS) is active
for more than 2 seconds. |
Cruise Control Description and Operation Without Throttle Actuator Control
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:
• | The powertrain control module (PCM) |
• | The Resume/Accel switch |
• | The torque converter clutch (TCC) brake switch |
• | The cruise control module |
• | The vehicle speed sensor |
Cruise Control Engaged
The cruise control system will engage and adjust vehicle speed based on the
activation of the following cruise control switches:
The cruise control switches are located on the multifunction/turn signal lever.
The cruise control module monitors the signal circuits of the cruise control
switches in order to determine when to capture and maintain the selected vehicle speed.
The cruise control module receives the vehicle speed signal from the powertrain control
module (PCM), via the vehicle speed signal circuit. The cruise control module is an
electronic controller and an electric stepper motor. The electric controller monitors
the vehicle speed and operates the electric stepper motor. The electric stepper motor
moves a strap that is attached to the cruise control cable in order to move the throttle
linkage. Voltage is supplied from the 15-amp PCM IGN 1 fuse to
the cruise control module via the ignition 1 voltage circuit.
Voltage is supplied from the 10-amp IGN E fuse, to the cruise
control switch via the ignition 1 voltage circuit. When the normally open cruise
control On/Off switch is turned ON, the switch closes and the cruise control module
detects a high signal voltage on the cruise ON switch signal circuit. When the normally
open Set/Coast switched is pressed, the switch closes and the cruise control module
detects a high signal voltage on the Set/Coast signal circuit. To engage the cruise
control system, the On/Off switch must be ON and the set button momentarily pressed.
The PCM will confirm that the cruise control enable criteria has been met. When the
PCM determines that the cruise control enable criteria has been met, the PCM will
open the normally grounded cruise control inhibit signal circuit. The cruise control
module will provide a ground to the cruise control engaged signal circuit to the PCM.
The cruise control module will record the selected vehicle speed. 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 cruise control module
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 1.6 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 cruise control module 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 cruise control module 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 1.6 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 cruise control
module.
Cruise Control Disengaged
The cruise control module disengages the cruise control operation based on the
signals from the following switches:
• | The torque convert clutch (TCC)/brake switch |
The TCC/brake switch and the stop lamp switch are used to disengage the cruise
control. The stop lamp and TCC/brake switch are incorporated into an assembly and
are mounted to the brake pedal bracket. When the brake pedal is pressed, the normally
closed TCC/brake switch opens and the normally open stop lamp switch closes. The cruise
control module detects a low signal voltage on the TCC/brake signal circuit and detects
a high signal voltage on the stop lamp signal circuit. The vehicle speed stored in
the memory of the cruise control module will be erased when the cruise control On/Off
switch is turned OFF, or the ignition switch is turned OFF.
Cruise Control Inhibited
The powertrain control module (PCM) inhibits the cruise control operation when
any of the following conditions exist:
• | The vehicle is in PARK, REVERSE, NEUTRAL, or 1st gear. |
• | The engine RPM is high. |
• | The vehicle speed is high. |
• | The system voltage is not between 9-16 volts. |
• | The antilock brake system/traction control system is active for more than
2 seconds. |
When the PCM detects a malfunction, or the cruise control criteria has not been
met, the PCM grounds the cruise control inhibit signal circuit, and the cruise control
module detects a low signal voltage.
Cruise Control Description and Operation 6.6L
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:
• | The engine control module (ECM) |
• | The Resume/Accel switch |
• | The torque converter clutch (TCC)/brake switch |
• | The throttle actuator control (TAC) module |
• | The vehicle speed sensor (VSS) |
Cruise Control Engaged
The cruise control system will engage and adjust vehicle speed based on the
activation of the following cruise control switches:
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 monitors the vehicle speed sensor signal circuit in order to determine the
vehicle speed. The ECM uses the throttle actuator control (TAC) motor in order control
the vehicle speed. Ignition positive voltage is supplied from the 10-amp IGN E fuse,
to the cruise control switch via the ignition 1 voltage circuit. When the normally
open cruise control On/Off switch is turned ON, the switch closes and the engine control
module detects a high signal voltage on the cruise On/Off switch signal circuit. When
the normally open Set/Coast switched is pressed, the switch closes and the engine
control module detects a high signal voltage on the Set/Coast signal circuit. To engage
the cruise control system, the On/Off switch must be ON and the set button momentarily
pressed. The ECM will confirm that the cruise control enable criteria has been met.
When the ECM determines that the cruise control enable criteria has been met, the
ECM will engage the cruise control system and record the selected vehicle speed. The
ECM will then send a class 2 message to the instrument panel cluster (IPC)
in order to activate 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 engine control module 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 1.6 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 engine control module 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 engine control module 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 1.6 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 engine control
module.
Cruise Control Disengaged
The engine control module (ECM) disengages the cruise control operation based
on the signals from the following switches:
• | The torque converter clutch (TCC)/brake switch |
The TCC/brake switch and the stop lamp switch are used to disengage the cruise
control. The stop lamp and TCC/brake switch are incorporated into an assembly and
are mounted to the brake pedal bracket. When the brake pedal is pressed, the normally
closed TCC/brake switch opens and the normally open stop lamp switch closes. The engine
control module detects a low signal voltage on the TCC/brake signal circuit and detects
a high signal voltage on the stop lamp signal circuit. The vehicle speed stored in
the memory of the engine control module will be erased when the cruise control On/Off
switch is turned OFF, or the ignition switch is turned OFF.
The cruise control system will disengage when the ECM detects that the driver
has the accelerator pedal override active for approximately 60 seconds.
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 control
indicator.
Cruise Control Inhibited
The engine control module (ECM) inhibits the cruise control operation
when any of the following conditions exist:
• | A Cruise Control System related DTC has been set. |
• | The vehicle speed is less than 40 km/h (25 mph). |
• | The vehicle is in PARK, REVERSE, NEUTRAL, or 1st gear. |
• | The engine RPM is too low. |
• | The engine RPM is too high. |
• | The vehicle speed is too high. |
• | The system voltage is not between 9-16 volts. |
• | The Antilock Brake System (ABS)/Traction Control System (TCS) is active
for more than 2 seconds. |